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BA427E intrinsically safe 2-wire 4/20mA manual set point station Issue 1
Issue: 11st August 2013
2
1. Description
2. Operation2.1 Controls2.2 Displays
3. Intrinsic Safety Certification3.1 ATEX gas certification3.2 Zones, gas groups & T rating3.3 Special conditions for safe use3.4 4/20mA output3.5 Certification label information
4. System Design for Hazardous Areas4.1 4/20mA loop using Zener barriers4.2 4/20mA loop using Galvanic
Isolators.
5. Installation5.1 Location5.2 EMC5.3 Instalation procedure5.4 Scale card
6. Configuration and Calibration6.1 Summary of configuration functions6.2 Adjustment resolution6.3 Position of decimal point6.4 Calibration of display using external
meter.6.5 Calibration of display using internal
reference.6.6 High & low current output limits6.7 Pre-set outputs6.8 Maximum output rate of change6.9 Function of P push button in operating
mode.6.10 Encoder6.11 Security code6.12 Reset to factory defaults
7. Maintenance7.1 Fault finding during commissioning7.2 Fault finding after commissioning7.3 Servicing7.4 Routine maintenance7.5 Guarantee7.6 Customer comments
8. Accessories8.1 Scale card8.2 Tag information8.3 Display backlight
8.3.1 Loop powering the backlight8.3.2 Separately powering the
backlight.8.4 Rotary encoder
Appendix 1 Dust certification
Appendix 2 IECEx certification
The BA427E is CE marked to show compliance with theEuropean Explosive Atmospheres Directive 94/9/EC
and the European EMC Directive 2004/108/EC
CONTENTS
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1. DESCRIPTIONThe BA427E is an intrinsically safe, loop powered,panel mounting Set Point Station which enables thecurrent flowing in a 4/20mA loop to be manuallyadjusted from within a hazardous process area viathe front panel push buttons, or an optional externalrotary control. The BA427E output is adjustablebetween 3 and 22mA but the output range may berestricted if only limited adjustment is required. Inaddition to the output being continuously variable,five pre-set output currents may be configured andsubsequently selected from the front panel pushbuttons. To minimise plant disturbance themaximum output rate of change may be defined.
Adjustment of a plant parameters represented by a4/20mA current is the main application for BA427ESet Point Stations. A controller set point, actuatorposition or any 4/20mA variable may be manuallyadjusted.
The BA427E incorporates a 5 digit display and a 31segment bargraph which may be calibrated todisplay the 4/20mA output current in any linearengineering units. An optional factory fittedbacklight, which may be loop or separately powered,enables this display to be read in all lightingconditions.
All BA427E Set Point Stations and the optionalbacklight have been certified intrinsically safe foruse in gas and dust hazardous areas by NotifiedBody Intertek Testing and Certification Ltd. Thiscertification has been used to confirm compliancewith the European ATEX Directive 94/9/EC.
For international applications the BA427E hasIECEx certification which is described in Appendix 2.
2. OPERATIONThis instruction manual describes ATEX systemdesign and installation for use of the BA427E in agas hazardous area. Please refer to Appendix 1 fordetails of ATEX dust certification and to Appendix 2for IECEx certiification.
Fig 1 shows a simplified block diagram of theBA427E manual Set Point Station. The 4/20mAcurrent flowing in the loop may be manually set atany value between approximately 3 and 22mA usingthe front and panel push buttons. Initially theoutput current changes slowly, but after the buttonhas been pressed for five seconds the rate ofchange accelerates to allow large changes to bemade quickly.
The five pre-set outputs, which are selectable via theinstruments front panel push butons, allow theoperator to quickly select frequently used plant setpoints.
To prevent plant disturbance the maximum rate ofoutput current change initiated by operating the frontpanel push buttons, switching between pre-setoutputs or using an optional external encoder maybe defined.
The output resistance of the BA427E is very high,within the specified operating voltage range, the loopcurrent will therefore be unaffected by changes inthe supply voltage.
CautionThe BA427E output should not be used for
critical safety applications.
Versatile calibration facilities allow the 5 digit internaldisplay to show the 4/20mA output current in linearengineering units. For example, in an applicationwhere the BA427E is being used to adjust the setpoint of a speed controller, the internal indicator maybe calibrated to display the required speed in RPM.
For applications in poorly illuminated areas a factoryfitted green backlight is available which may be loopor separately powered. When loop powered thebacklight produces background illumination enablingthe display to be read at night or in poor lightingconditions. No additional power supply, intrinsicsafety interface or field wiring are required, but theSet Point Station voltage drop is increased. Whenseparately powered, the backlight is brighter but anadditional intrinsic safety interface and field wiringare required.
Fig 1 Simplified block diagram of BA427E
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2.1 ControlsThe BA427E Set Point Station is controlled andconfigured via four front panel push buttons locatedbelow the display. In the operating mode i.e. whenthe Set Point Station is controlling the loop currentand the display is showing the output in engineeringunits, these push buttons have the followingfunctions:
E + ▼ Output current slowly decreases. After fiveseconds the rate of change accelerates sothat large changes may be made quickly..Use of two buttons minimises possibility ofaccidental adjustment.
E + ▲ Output current slowly increases. After fiveseconds the rate of change accelerates sothat large changes may be made quickly..Use of two buttons minimises possibility ofaccidental adjustment.
E Continuously pushing this button for 5seconds allows the Set Point Stationoutput to be entered in engineering unitsdigit by digit using the ▲ or ▼ push buttonto adjust the flashing digit and the P buttonto move control to the next digit. Whenset as required, pressing the E button willenter the new set point.
P While this button is pushed the BA427ESet Point Station will display one of threealternatives depending upon how theinstrument has been configured:
Output current mA without bargraph
Output as a % of span
Pre-set outputs in engineering unitsThe display will flash. Whilecontinuing to press the P button,operating the ▼ or ▲ button willshow the identification of the pre-setclosest to the present Set PointStation output, followed by the pre-set value. Operating the ▼ or ▲button will scroll through the fivepre-sets and an ‘Abort’ position.Releasing both buttons will leave theselected pre-set value or ‘Abort’legend flashing for ten seconds,during which time operating the Ebutton will update the Set PointStation output to the displayed pre-set value. If the E button is notoperated during this period, the SetPoint Station output will not bechanged and the originalengineering display will be shown.
▼ While this button is pushed the Set PointStation will display the numerical value andanalogue bargraph the Set Point Stationhas been calibrated to display with a 4mA*output. When released the normal displayin engineering units will return.
▲ While this button is pushed the Set PointStation will display the numerical value andanalogue bargraph the Set Point Stationhas been calibrated to display with a20mA* input. When released the normaldisplay in engineering units will return.
* If the Set Point Station display has beencalibrated using the CAL function,calibration points may not be at 4 and20mA.
P + ▼ Firmware number followed by version.
P + E Access to configuration menu via optionalsecurity code.
2.2 DisplaysThe BA427E Set Point Station has a 5 digit displayplus a 31 segment bargraph.
The digital display may be calibrated using the ‘CAL’or ‘5Et’ functions to display the engineering variablerepresented by the Set Point Station’s 4/20mAoutput, such as temperature, pressure or speed.
The digital display shows the requested Set PointStation output in engineering units, the digital displaywill flash until the Set Point Station output is thesame as the requested output.
The bargraph, which is not adjustable, always showsthe actual Set Point Station output. The bargraphstarts and finishes at the two currents at which thedigital display was calibrated, usually 4 and 20mA.See sections 6.4 and 6.5.
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3. INTRINSIC SAFETY CERTIFICATIONAll BA427E Set Point Stations have ATEX andIECEx gas and dust intrinsic safety certification.This section of the instruction manual describesATEX gas certification. ATEX dust and IECExapprovals are described in Appendixes 1 and 2.
3.1 ATEX gas certificationNotified Body Intertek Testing and Certification Ltdhave issued the BA427E Set Point Station with anEC-Type Examination Certificate numberITS12ATEX27718X. This confirms compliance withharmonised European standards and it has beenused to confirm compliance with the EuropeanATEX Directive for Group II, Category 1Gequipment, Ex ia IIC T5 Ga Ta = -40 to +70ºC.The Set Point Station carries the community markand subject to local codes of practice may beinstalled in any of the European Economic Area(EEA) member countries. ATEX certificates are alsoacceptable for installations in Switzerland.
This section of the instruction manual describesATEX installations in explosive gas atmospheresconforming with EN60079-14 Electrical Installationsdesign, selection and erection. When designingsystems for installation outside the UK the localCode of Practice should be consulted.
3.2 Zones, gas groups and T ratingThe BA427E Set Point Station has been certifiedEx ia IIC T5 Ga. When connected to a suitablesystem the Set Point Station may be installed in:
Zone 0 explosive gas air mixturecontinuously present.
Zone 1 explosive gas air mixture likelyto occur in normal operation.
Zone 2 explosive gas air mixture notlikely to occur, and if it doeswill only exist for a short time.
Be used with gases in groups:Group A propaneGroup B ethyleneGroup C hydrogen
Having a temperature classification of:T1 450oCT2 300oCT3 200oCT4 135oCT5 100oC
At ambient temperatures between -40 and +70oC.
This allows the BA427E Set Point Station to beinstalled in all gas Zones and to be used with mostcommon industrial gases except carbon disulphideand ethyl nitrite which have an ignition temperatureof 95ºC.
3.3 Special conditions for safe useThe BA427E ATEX certificate has an ‘X’ suffixindicating that special conditions apply forinstallations in IIIC conductive dust atmospheres.No special conditions apply for installations in gas orin IIIA and IIIB dust atmospheres. See Appendix 1for information about use in dust atmospheres.
3.4 4/20mA outputInput safety parameters for the 4/20mA output,terminals 1 and 3 are:
Ui = 30V dcIi = 200mAPi = 0.84W
Equivalent maximum capacitance and inductancebetween the two 4/20mA output terminals 1 and 3 is:
Ci = 2.2nFLi = 0.01mH (8µH)
Maximum permitted loop cable parameters can becalculated by adding these figures to Ci and Li ofother instruments in the loop and subtracting thetotals from the maximum cable capacitance Co andcable inductance Lo permitted for the Zener barrier,galvanic isolator or associated apparatus poweringthe loop.
3.5 Certification label informationThe certification information label is fitted in a recesson the top outer surface of the instrument enclosure.It shows the ATEX certification information,instrument serial number, year of manufacture plusBEKA associates name and location. NonEuropean certification information may also beincluded, a typical label is shown below.
BA427E certification label
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4. SYSTEM DESIGN FOR HAZARDOUSAREAS
4.1 4/20mA loop using Zener barriersFig 2 illustrates a typical application in which aBA427E Set Point Station mounted in a hazardousarea is being used to adjust the setpoint of a speedcontroller located in a safe area. To enable thenegative side of both the speed controller and thepower supply to be connected together and earthed,a Zener barrier is required in series with both theoutgoing and return wires connected to the BA427ESet Point Station.
The Zener barrier(s) should be ATEX certified withcombined output parameters equal to or less thanthe maximum BA427E input safety parameters.Most Zener barriers are certified Ex ia IIC allowingthem to be connected to equipment located in anyZone and to be used with any gas group thussimplifying selection.
For this application a wide range of devices may beused. A 28V; 93mA positive polarity device in theoutgoing wire and a diode return barrier in the returnwire are industry standard devices which areavailable from most barrier manufactures oftenhoused in a single package.
The maximum permitted cable parameters are thosespecified by the Zener barrier certificate, less thesum of equivalent input capacitance and inductanceCi & Li of all the other instruments in the loop, in thisexample just the BA427E.
When designing the loop it is necessary to establishthat the maximum voltage drop caused by the SetPoint Station, both Zener barrier channels, the load(speed controller input) and the cable resistance isalways less than the minimum power supply voltage.
Fig 2 Typical application using barriers
In this example:
Minimum operating voltage of BA427E 6.1V
Maximum voltage drop caused by 28V 6.8V93mA Zener barrier(340 end-to- end resistance x 20mA)
Maximum voltage drop caused by 1.3Vdiode return barrier
Maximum voltage drop caused by 5.0Vspeed controller input.(250 x 20mA)
Maximum voltage drop caused by 0.2Vcable resistance(10 x 20mA)
______Total maximum voltage drop 19.4V
The minimum power supply voltage must thereforebe above 19.4V, but below 25.5V which is themaximum working voltage of a typical 28V Zenerbarrier.
If the BA427E Set Point Station includes an optionalbacklight which is loop powered, the minimumoperating voltage of the instrument increases from6.1 to 10V. See section 8.3.1
4.2 4/20mA loop using Galvanic IsolatorsGalvanic isolators, although more expensive thanZener barriers, do not require a high integrity earthconnection. For small systems where a highintegrity earth is not already available, the use ofgalvanic isolators often reduces the overallinstallation cost.
The example described in section 4.1 can besimplified by the use of a galvanic isolator as shownin Fig 3.
Fig 3 Typical application using a galvanic isolator
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Any 4/20mA ATEX certified 4/20mA galvanic isolatorwith output safety parameters equal to or less thanthe maximum BA427E certified input parametersmay be used.
The maximum permitted cable parameters are thosespecified on the galvanic isolator certificate, less thesum of equivalent input capacitance and inductanceCi & Li of all the other instruments in the loop, in thisexample just the BA427E.
When designing the loop it is necessary to ensurethat the supply voltage between terminals 1 & 3 ofthe BA427E Set Point Station always exceeds 6.1Vwhich is the minimum operating voltage.
If the BA427E Set Point Station includes an optionalbacklight which is loop powered, the minimumoperating voltage of the instrument increases from6.1 to 10V. See section 8.3.1
5. INSTALLATION
5.1 LocationThe BA427E Set Point Station has a robust glassreinforced modified PPO enclosure with atoughened glass window. The front of theinstrument has IP66 protection and a gasket sealsthe joint between the Set Point Station enclosureand the panel. The rear of the instrument has IP20protection.
Installation may therefore be in any panel providingthat the operating temperature is between –40ºCand +70ºC and intrinsic safety requirements aresatisfied.
Fig 4 shows the overall dimensions of the BA427Etogether with the recommended panel cut-outdimensions and terminal identifications. To achievean IP66 seal between the instrument enclosure andthe instrument panel an aperture with therecommended tolerance should be used.
The BA427E certification label carries a warning:
‘Potential electrostatic charging hazardclean only with a damp cloth’
Care should be taken when cleaning the front of theinstrument, although the warning only applies to thecase as the glass window and keypad will notsupport a static charge.
Fig 4 BA427E dimensions
CautionAlthough the front of the Set Point
Station has IP66 protection, it should beshielded from direct sunlight and severe
weather conditions.
5.2 EMCBA427E Set Point Stations comply with therequirements of the European EMC Directive2004/108/EC. For specified immunity all wiringshould be in screened twisted pairs, with the cablescreen earthed at one point within the safe area.
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5.3 Installation Procedure
a. Cut the specified aperture in the panel. Toachieve an IP66 seal between the instrumentenclosure and the instrument panel theaperture must have the dimensions specifiedin Fig 4.
b. Slide the gasket over the body of the Set PointStation before inserting the instrument into thepanel aperture.
c. Firstly ensure that both the panel mountingclamps are closed by turning the knurledscrews fully anti clockwise until the two pips inthe clamp foot align with holes in the clampbody.
d. Place a clamp in the recess on each side ofthe Set Point Station, pulling gently to slide itonto the dovetail as shown in Fig 5. Push theknurled screw slightly forward to engage thethread and tighten by turning clockwise until itis just finger tight. When both clamps are fittedensure that the gasket behind the front panelbezel is correctly positioned before fullytightening the clamps to secure the instrument.The maximum recommended clamp tighteningtorque is 22cNm (1.95 lbf in) which isapproximately equvalent to finger-tight plusone half turn. Do not over tighten.
e. Connect the panel wiring to the rear terminalblock(s) as shown in Fig 4. To simplifyinstallation, the terminals are removable sothat the panel wiring can be completed beforethe instrument is installed.
Fig 5 Fitting panel mounting clamps
5.4 Scale cardThe engineering units of measurement represent bythe Set Point Station’s 4/20mA output current maybe shown on a printed scale card in a window at theright hand side of the display. The scale card ismounted on a flexible strip that is inserted into a slotat the rear of the instrument as shown in Fig 6.Thus the scale card can easily be changed withoutremoving the Set Point Station from the panel oropening the instrument enclosure.
New instruments are supplied with a printed scalecard showing the requested units of measurement, ifthis information is not supplied when the instrumentis ordered a blank card will be fitted.
A pack of self-adhesive scale cards printed withcommon units of measurement is available as anaccessory from BEKA associates. Custom printedscale cards can also be supplied.
To change a scale card, unclip the end of the flexiblestrip that is accessible from the rear of theinstrument by gently pushing the strip upwards andpulling it out of the enclosure. Peel the existingscale card from the flexible strip and replace it with anew printed card, which should be aligned as shownin Fig 6. Do not fit a new scale card on top of anexisting card.
Install the new scale card by gently pushing theflexible strip into the slot at the rear of the Set PointStation, when it reaches the internal end-stopsecure it by pushing the end of the flexible stripdownwards so that the tapered section is held by therear panel.
Align the self-adhesive printedscale card onto the flexible stripand insert the strip into the SetPoint Station as shown below.
Fig 6 Inserting flexible strip carrying scale card into slot at the rear of Set Point Station.
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6. CONFIGURATION AND CALIBRATIONSet Point Stations are configured and calibrated viathe four front panel push buttons. All theconfiguration functions are contained in an easy touse intuitive menu that is shown diagrammaticallyin Fig 7.
Each menu function is summarised in section 6.1and includes a reference to more detailedinformation.
Throughout this manual push buttons are shown asP, E, ▼ or ▲ and the Set Point Station displaylegends are shown within inverted commas e.g.'CAL' and 'CodE'.
Access to the configuration menu is obtained byoperating the P and E push buttons simultaneously.If the Set Point Station security code is set to thedefault 0000 the first parameter 'rE5n' will bedisplayed. If a security code other than the defaultcode 0000 has already been entered, the Set PointStation will display 'CodE'. Pressing the P buttonwill result in ‘0000’ being displayed with one digitflashing. To gain access the four digit security codeshould be entered using the ▲ and ▼ push buttonsto set the flashing digit and the P button to movecontrol to the next digit. When the correct four digitcode has been entered, pressing E will cause thefirst parameter 'rE5n' to be displayed. If the code isincorrect, or a button is not pressed within twentyseconds, the Set Point Station will automaticallyreturn to the operating mode.
Once within the configuration menu the requiredparameter can be reached by scrolling through themenu using the ▲ or ▼ push buttons as shown inFig 7. When returning to the operating modefollowing recalibration or a change to any function,the Set Point Station will display ‘dAtA’ followed by‘SAVE’ while the new information is stored inpermanent memory.
All new Set Point Stations are supplied calibrated asrequested at the time of ordering. If calibration is notrequested, instruments will be supplied with thefollowing default configuration:
Default Configuration
Resolution ‘rE5n’ 10Display at 4mA output ‘2ero’ 0.00Display at 20mA output ‘5PAn’ 100.00Output current limits ‘H - - L’ 03.000 & 22.000Maximum output rate of change 000P button in operating mode ‘P.Fn’ PCPulses per rev of external encoder ‘EnC’ 12Security access code ‘CodE’ 0000
Default configuration can easily be changed on-site.
6.1 Summary of configuration functionsThis section summarises each of the configurationfunctions and includes a cross reference to a moredetailed description. Fig 7 illustrates the location ofeach function within the configuration menu.
Display Summary of function
'rE5n' Adjustment resolutionDefines the adjustment resolution of thefront panel ▲ and ▼ buttons and theoptional external rotary control whenadjusting the output current with the SetPoint Station in the operating mode.May be set to ‘1’, ‘10’ or ‘100’ leastsignificant digits of the display.See section 6.2
'dP' Decimal pointPositions a dummy decimal pointbetween any of the displayed digits orturns it off.See section 6.3
‘CAL’ and ‘SEt’ are alternative ways ofcalibrating the Set Point Station digital display.
'CAL' Calibration of the digital display usingan external current meter.Preferred method of calibrating the digitaldisplay which enables the zero and spanof the Set Point Station display to becalibrated to show the engineering unitsrepresented by the 4/20mA output.Calibration may be performed at anyoutput current providing the points are atleast 4mA apart. Requires an accurateexternal current meter.See section 6.4
'5Et' Calibration of digital display usinginternal references.Using the Set Point Station’s internalreference, this function enables thedigital display to be calibrated to showthe engineering units represented by theoutput current at 4mA and 20mA.Unlike the ‘CAL’ function, an accurateexternal current measuring instrument isnot required and the Set Point Stationdoes not have to be disconnected fromthe loop, but calibration can only beperformed at 4 and 20mA.See section 6.5
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Display Summary of function
'H - - L' High & low current output limitsDefines the lower ‘Lo’ and upper ‘Hi’4/20mA Set Point Station output currentlimits.See section 6.6
'P5Et' Pre-set outputsThe values of the five pre-set currentoutputs are defined by this function. Thepre-set output currents are identified‘5Et1’ to ‘5Et5’ and are displayed inengineering units.This function only appears in theconfiguration menu when ‘P5Et’, whichallows pre-set values to be viewed andselected in the operating mode, isselected in the ‘P.Fn’ function.See section 6.7
'rAtE' Maximum output rate of changeEnables the maximum rate of change ofthe 4/20mA output current to be defined.Adjustable between approximately 1 and100 seconds for full scale output travel.0 disables this rate of change limit.See section 6.8
'P.Fn' Function of P push button inoperating mode.The Set Point Station may be configuredto display the output current in milliamps,the output current as a percentage or toprovide access to the five pre-set outputswhen the P push button is pressed in theoperating mode.See section 6.9
'EnC' EncoderIn addition to the Set Point Station4/20mA output being adjusted by thefront panel push buttons, an externalquadrature encoder may be connected toprovide control via a rotary knob. Thisfunction allows the number of pulses perrevolution of the knob to be entered.See section 6.10
Display Summary of function
'CodE' Security codeDefines a four digit numeric code thatmust be entered to gain access to theconfiguration menu. Default code 0000disables this security function and allowsunrestricted access to all conditioningfunctions.See section 6.11
'r5Et' ResetReturns the Set Point Stationconfiguration to the default condition. Toprevent accidental use, reset must beconfirmed by entering ‘5urE’ before it willbe executed.See section 6.12
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11
12
6.2 Adjustment resolution: ‘rE5n’This function enables the adjustment resolution ofthe front panel ▲ and ▼ buttons and the optionalalternative external rotary control to be defined. Oneof three different resolutions may be selected ‘1’, ‘10’or ‘100’ least significant digits of the Set PointStation display. If ‘10’ is selected the leastsignificant displayed digit will always be zero and thesecond least significant digit will change when thefront panel E button plus the ▲ or ▼ button arepressed in the operating mode, or the optionalexternal rotary control is turned. Similarly, if ‘100’ isselected the least two significant displayed digits willalways be zero and the third least significant digitwill change when the front panel buttons areoperated, or the optional external rotary control isturned.
To define the adjustment resolution select ''rE5n'from the configuration menu and press P which willreveal the current adjustment resolution. To changethe resolution press the ▲ or ▼ button to select 1,‘10’ or ‘100’, followed by the E button to enter theselection and return to the configuration menu.
Notes:a. This function does not affect the resolution of
adjustments made within the configurationmenu.
b. If a pre-set output has a finer resolution thanthe selected adjustment resolution, the finerresolution will be used to determine the pre-setoutput, but the selected resolution will berestored when the output is adjusted using theE button plus the ▲ or ▼ button in theoperating mode,
6.3 Position of the decimal point: ‘dP’A dummy decimal point can be positioned betweenany of the displayed digits or it may be absent. Toposition the decimal point, select 'dP' from theconfiguration menu and press P. The decimal pointcan be moved by pressing the ▲ or ▼ push button.If a decimal point is not required it should bepositioned beyond the most or least significant digit.When positioned as required press the E button toenter the selection and return to the ‘dP’ prompt inthe configuration menu.
6.4 Calibration of the digital display using anexternal current meter: ‘CAL’This function is the preferred method of calibratingthe Set Point Station digital display to show theengineering units represented by the 4/20mA output.The function enables the Set Point Station outputcurrent to be set at two different values, Zero andSpan, measured by a calibrated external current
meter and the corresponding Set Point Stationdisplay to be entered.
The bargraph is not displayed while using the ‘CAL’function.
Although calibration is normally performed at4.000mA and 20.000mA, other currents may beused providing they differ by more than 4mA.
To calibrate the Set Point Station display, select'CAL' from the configuration menu and press P toenter the ‘2Ero’ sub-menu used for calibrating thedisplay at the lower of the two output currents,usually 4.000mA. Pressing P again will result in‘Adj’ being displayed which is an invitation to adjustthe Set Point Station output current using the ▲ or▼ push button. Pressing either of these buttons willcause the output current to change, graduallyaccelerating as the button is held. Alternatively theexternal rotary encoder may be used. When theexternal current meter shows the required loweroutput current e.g. 4.000mA, press P to reveal theexisting Set Point Station digital display with onedigit flashing. The flashing digit may be adjusted bypressing the ▲ or ▼ button, when this digit is set asrequired pressing P will transfer control to the nextdigit. When all the digits have been adjusted, pressE to enter the setting and return to the '2Ero' prompt.
Calibration of the Set Point Station display at theupper output current is performed in exactly thesame way using the ‘5PAn’ sub-menu which may beselected from the ‘2ero’ prompt using the ▲ or ▼button.
To obtain a reverse acting display i.e. the Set PointStation display decreases as the output currentincreases, the required display value entered into‘2Ero’ should be greater than that entered into‘5PAn’. The ▲ and ▼ buttons on the front of theinstrument always indicate which way the display willchange when the button is pushed.
The bargraph will start at the numerical displayentered for ‘2Ero’ calibration and finish at thenumerical display entered for ‘5Pan’ calibration,except for reverse acting calibration when thebargraph will also be reversed.
Note:a. If the specified ‘2Ero’ and ‘5PAn’ output
currents do not differ by 4 or more milliamps,they will not be stored when the E button ispressed to return the Set Point Station to theoperating mode.
6.5 Calibration of digital display using internalreference: ‘5Et’
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Using the Set Point Station’s internal reference, thisfunction enables the digital display to be calibratedto show the engineering units represented by theoutput current at 4mA and 20mA. Unlike the ‘CAL’function, an accurate external current measuringinstrument is not required and the Set Point Stationdoes not have to be disconnected from the loop,however calibration can only be performed at 4mAand 20mA. Although not traceable to a calibratedstandard, accuracy is adequate for many industrialapplications.
To calibrate the Set Point Station’s digital displayselect 'SEt' from the configuration menu and pressP. The Set Point Station will display '4.000',pressing P again will reveal the calibrated display at4mA output with one digit flashing. The flashingdigit may be adjusted by pressing the ▲ or ▼buttons, when the flashing digit is correct pressing Pwill transfer control to the next digit. When all thedigits have been adjusted, press E to return to the'4.000' prompt.
Calibration of the Set Point Station display at 20mAoutput is performed in exactly the same way usingthe ‘20.000’ sub-menu which may be selected fromthe ‘4.000’ prompt using the ▲ or ▼ button. Whenthe display corresponding to a 20mA output hasbeen entered pressing E twice will enter the settingand return to the ‘5Et’ prompt in the configurationmenu.
The bargraph is not displayed while using the ‘5Et’function
To obtain a reverse acting display i.e. the Set PointStation display decreases as the output currentincreases, the required display value entered into‘4.000’ should be greater than that entered into’20.000’. The ▲ and ▼ buttons on the front of theinstrument always indicate which way the display willchange when the button is pushed.
The bargraph will start at the numerical displayentered for 4mA output and finish at the numericaldisplay entered for 20mA output, except for reverseacting calibration when it will also be reversed.
6.6 High & low current output limits: ‘H - - L’The BA427E output is normally adjustable between3 and 22mA, but may be restricted by this function ifa limited adjustment range is required. e.g. toprevent a dangerously high and/or low temperaturebeing selected when used as the set point input fora temperature controller. When the Set PointStation’s output current equals the high limit, ‘oVEr’is displayed, similarly ‘undEr’ is displayed when theoutput current equals the low limit.
To restrict the Set Point Station’s output currentrange select 'H - - L' from the configuration menuand press P. Using the ▲ or ▼ button select ‘Lo’ toadjust the lower current output limit, or ‘Hi’ to adjustupper output current limit. Pressing E will displaythe selected output current limit in milliamps withone digit flashing. The flashing digit may be adjustedby pressing the ▲ or ▼ button, when the flashingdigit is correct pressing P will transfer control to thenext digit. When all the digits have been adjustedpress E to return to the 'Lo' or ‘Hi’ prompt followedby E to enter the adjustments and return to the ‘H - -L’ prompt in the configuration menu.
Notes:a. The Lo limit can not be adjusted to a value
above the present Set Point Station outputcurrent, and the Hi limit can not be adjusted toa value below the present Set Point Stationoutput current. The actual Set Point Stationoutput current should therefore be adjusted towithin the acceptable output range before theLo and Hi limits are adjusted.
b. If any of the five pre-set output currents are setbelow the Lo limit or above the Hi limit, they willnot be selectable and ‘oVEr’ or ‘undEr’ will bedisplayed.
6.7 Pre-set outputs: ‘P5Et’Up to five pre-set current outputs may be stored andrecalled from the front panel push buttons whichenables common output currents to be quicklyselected. e.g. frequently used operatingtemperatures when a BA427E is used as the setpoint input for a temperature controller.
To enter pre-set values select ‘P5Et’ from theconfiguration menu and press P which will result in‘5Et 1’, the first pre-set sub-menu being displayed,pressing P will then reveal the present value inengineering units with one digit flashing. Theflashing digit may be adjusted by pressing the ▲ or▼ button, when the flashing digit is correct pressingP will transfer control to the next digit. When all thedigits have been adjusted, press E to return to the'5Et 1' prompt from which any of the other four pre-sets may be selected via the ▲ or ▼ button andadjusted in the same way as ‘5Et 1’.
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Notes:a. ‘P5et’ only appears in the configuration menu
when ‘P5Et’ is selected in the ‘P.Fn’ menuwhich defines the function of the P push buttonin the operating mode. see section 6.9.
b. Maximum adjustment resolution is alwaysavailable for inputting pre-set values and isused to determine the current output when thepre-set is selected, irrespective of theadjustment resolution selected in function‘rE5n’ – see 6.2
c. If, after calibration of the Set Point Stationdisplay, previously entered pre-set values areoutside the revised output current range, whenselected the pre-set value alternating with‘oVEr’ or ‘undEr’ will be displayed.
6.8 Maximum output rate of change: ‘rAtE’To minimise plant disturbance when the Set PointStation output current is adjusted, the maximum rateof change is defined by this function. The maximumrate is adjustable between approximately 1 and 100seconds for full scale output travel from 4 to 20mA.If 0 seconds is selected the function is disabled.
To define the maximum rate of change of the SetPoint Station output select 'rAtE' from theconfiguration menu and press P which will reveal thepresent maximum rate of change in seconds withone digit flashing. The flashing digit may beadjusted by pressing the ▲ or ▼ buttons, when theflashing digit is correct pressing P will transfercontrol to the next digit. When all the digits havebeen adjusted, press E to enter the new value andreturn to the configuration menu.
When the output rate of change limitation isfunctioning, in the operating mode the Set PointStation digital display will show the requested outputand will flash until the requested output current isachieved. The bargraph display always shows theSet Point Station’s actual output.
Pressing the E button while the output is ramping toa new requested value will stop the output changing.
6.9 Function of the P push-button in operatingmode: ‘P.Fn’Using this function the Set Point Station may beconfigured to display the output current in milliamps,the output current as a percentage of the outputrange, or to provide access to the five pre-setoutputs when the P button is pressed in theoperating mode.
To check or change the function of the P pushbutton select 'P.Fn' from the configuration menu andpress P to reveal the present setting. Pressing the▲ or ▼ button will scroll the setting between:
'PC' Output as a percentage of outputrange.
'4-20' Output current in milliamps
‘P5Et’ Access to the five pre-set outputssee 6.7
When set as required, press E to return to the ‘P.Fn’prompt in the configuration menu.
6.10 Encoder: ‘EnC’For applications requiring the Set Point Station’s4/20mA output current to be controlled by a rotaryknob, an external three wire quadrature encodermay be directly connected to terminals 5, 6 and 7.The BEKA BA490 Is a panel mounting encoder thatgenerates 12 contact pulses per revolution whichcomplies with the requirements for simple apparatusand is intended for use with the BA427E. Otherencoders that produce a different number of contactpulses per revolution may also be used. So that allexternal encoders have a similar adjustmentresolution, the ‘EnC’ function enables the number ofpulses between 6 and 48 per revolution to bedefined.
To enter the number of pulses per revolution that theexternal encoder generates, select 'EnC' from theconfiguration menu and press P which will reveal theexisting setting with one digit flashing. The flashingdigit may be adjusted by pressing the ▲ or ▼button, when the flashing digit is correct pressing Pwill transfer control to the other digit. When bothdigits have been adjusted press E to return to the‘EnC’ prompt in the configuration menu.
Section 8.4 contains information about the use of anexternal rotary encoder.
6.11 Security code: ‘CodE’Access to the instrument configuration menu may beprotected by a four digit security code which must beentered to gain access. New instruments areconfigured with the default security code 0000 whichallows unrestricted access to all configurationfunctions.
To enter a new security code select 'CodE' from theconfiguration menu and press P which will cause theSet Point Station to display the existing securitycode with one digit flashing. The flashing digit canbe adjusted using the ▲ and ▼ push buttons, whenset as required operating the P button will transfercontrol to the next digit.
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When all the digits have been adjusted press E toreturn to the ‘CodE’ prompt. The revised securitycode will be activated when the Set Point Station isreturned to the operating mode. Please contactBEKA associates sales department if the securitycode is lost.
6.12 Reset to factory defaults: ‘rSEt’This function quickly returns to the BA427E SetPoint Station to the factory default configurationsshown in section 6.
To reset the Set Point Station select ‘rSEt’ from theconfiguration menu and press P. To preventaccidental resetting the request must be confirmedby entering ‘5urE’. Using the ▲ button set the firstflashing digit to ‘5’ and press P to transfer control tothe second digit, which should be set to ‘u’. When‘5urE’ has been entered pressing the E button willreset the configuration menus and return the displayto the ‘rSEt’ function in the configuration menu.
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7. MAINTENANCE
7.1 Fault finding during commissioningIf a BA427E Set Point Station fails to function duringcommissioning the following procedure should befollowed:
Symptom Cause SolutionNo loop current Incorrect wiring Check wiring
There should be6.1 to 30Vbetween terminals1 & 3 with terminal1 positive.
With an optionalbacklight which isloop powered,there should be10V to 30Vbetween terminals3 & 12 withterminal 12positive.
No loop current0V betweenterminals 1 & 3 orbetween terminals3 & 12 if optionalbacklight is looppowered.
Incorrect wiringor no powersupply
Check supplyvoltage andvoltage dropcaused by all theinstruments in theloop.
Unstable 4/20mAloop current.
Noisy powersupply orinsufficientvoltage to powerall theinstruments inthe loop.
Eliminate ripple onpower supply orincrease supplyvoltage.
Unable to enterconfigurationmenu.
Incorrectsecurity codeentered.
Enter correctsecurity code, orcontact BEKA ifthe code has beenlost.
BA427E displays‘LP Lo’
Voltage betweenBA427E terminal1 & 3 is too low,
Increase 4/20mAloop supplyvoltage.
7.2 Fault finding after commissioning
ENSURE PLANT SAFETY BEFORESTARTING MAINTENANCE
Live maintenance is permitted onintrinsically safe equipment installedin a hazardous area, but onlycertified test equipment should beused unless a gas clearancecertificate is available.
If a BA427E Set Point Station fails after it has beenfunctioning correctly follow the procedure shown insection 7.1. If this does not reveal the cause of thefault, it is recommended that the Set Point Station isreplaced.
7.3 ServicingWe recommend that faulty BA427E Set PointStations are returned to BEKA associates or to ourlocal agent for repair.
7.4 Routine maintenenceThe mechanical and electrical condition of theinstrument should be regularly checked. Initiallyannual inspections are recommended, but theinspection frequency should be adjusted to suit theenvironmental conditions.
7.5 GuaranteeSet Point Stations which fail within the guaranteeperiod should be returned to BEKA associates orour local agent. It is helpful if a brief description ofthe fault symptoms is provided.
7.6 Customer commentsBEKA associates is always pleased to receivecomments from customers about our products andservices. All communications are acknowledgedand whenever possible, suggestions areimplemented.
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8. ACCESSORIES8.1 Scale cardThe BA427E Set Point Station has a window on theright hand side of the display through which thescale card showing the units represented by theoutput current such as ºC or mBar can be seen.New Set Point Stations are fitted with a scale cardshowing the units specified when the instrument wasordered, if the units are not specified when theinstrument is ordered a blank scale card will befitted. A pack of scale cards pre-printed withcommon units of measurement is available as anaccessory. These can easily be fitted to the SetPoint Station without opening the instrumentenclosure or removing it from the panel, Seesection 5.4 of this instruction manual.
Custom scale cards for applications requiring lesscommon units of measurement are also available.
8.2 Tag informationNew Set Point Stations can be supplied with tag orapplication information thermally printed onto therear panel adjacent to the terminals. This taginformation is not visible from the front of theinstrument after installation.
8.3 Display backlightThe BA427E Set Point Station can be supplied witha factory fitted green backlight that may be loop orseparately powered.
When loop powered the backlight producesbackground illumination enabling the display to beread at night or in poor lighting conditions. Noadditional power supply, intrinsic safety interface orfield wiring are required, but the Set Point Station’sminimum operating voltage is increased. Whenseparately powered the backlight is brighter, but anadditional intrinsic safety interface and field wiringare required.
Fig 8 Terminals for optional backlight
8.3.1 Loop powering the backlightThe backlight is loop powered by connecting it inseries with the Set Point Station’s 4/20mA output asshown in Fig 9, which increases the minimumoperating voltage to 10V.
Fig 9 Loop powered backlight
The input intrinsic safety parameters of thecombined Set Point Station and backlight are thesame as for the Set Point Station alone. Providingthe increased voltage drop can be tolerated, theintrinsic safety and system design described insections 3 and 4 of this manual remain valid with thebacklight loop powered.
9.3 .2 Separately powering the backlightThe optional backlight may also be powered from aseparate safe area power supply via an intrinsicallysafe interface as shown in Fig 10.
Fig 10 Separately powered backlight
When separately powered the backlight draws aconstant current of 22.5mA at or above 9V. Belowthis voltage the backlight continues to function butwith reduced brilliance. Powering the backlight froman adjustable voltage supply allows the backlightbrilliance to be adjusted which is a useful featurewhen the operator’s night vision has to bepreserved.
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Any certified Zener barrier or galvanic isolator maybe used to separately power the backlight, providingthe output parameters do not exceed:
Uo = 30V dcIo = 200mAPo = 0.84W
The internal capacitance Ci between terminals 12 &14 should be subtracted from Co of the intrinsicallysafe interface powering the backlight to determinethe maximum permissible cable capacitance.
Ci = 11nFLi = 0
Two separately powered BA427E Set Point Stationbacklights may be connected in parallel to a singlechannel 28V, 93mA Zener barrier or galvanicisolator with no noticeable reduction in brilliancewhen powered from a 24V dc supply.
8.4 External encoderFor applications requiring the output of the BA427ESet Point Station to be controlled externally,terminals 5, 6 and 7 enable a wide range of threewire quadrature encoders with switch contactoutputs to be directly connected to the BA427E. Toprevent accidental adjustment, the encoder onlychanges the Set Point Station’s output when the Ebutton is operated. The Set Point Station’s outputcurrent can still be controlled by the ▲ and ▼buttons when an external encoder is connected.
8.4.1 Intrinsic safetyThe intrinsic safety parameters for the externalencoder terminals 5, 6 and 7 are:
Ui = 30V dcIi = 200mAPi = 0.84W
Uo = 5.0V dcIo = 1.0mAPo = 1.25mW
Equivalent maximum capacitance and inductancebetween the three encoder terminals 5, 6 and 7 is:
Ci = 0Li = 0
These parameters are not restrictive and allow awide range of three wire quadrature encoders with aswitch contact output to be directly connected to theBA427E Set Point Station.
8.4.2 System design for hazardous areasThe external encoder must be certified intrinsicallysafe with input parameters equal to or greater than:
Ui = 5.0V dcIi = 1.0mAPi = 1.25mW
or output parameters equal to or less than:
Uo = 30V dcIo = 200mAPo = 0.84W
Alternatively, the encoder must comply with therequirements for simple apparatus as specified inClause 5.7 of EN 60079-11. Most encoderscomprising of just two mechanically activatedswitches will comply with these requirements. See8.4.3.
8.4.3 BEKA BA490 rotary encoderThe BEKA BA490 quadrature output rotary encoderhas been designed to operate with the BA427E SetPoint Station. It is an IP66 panel mounting devicewith a 18mm diameter control knob which complieswith the requirements for simple apparatus. Thetwo output waveforms and connections are shown inFig 12.
Fig 12 BA490 rotary encoder output waveforms
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APPENDIX 1Dust certification
A1.0 ATEX dust certificationIn addition to ATEX certification permittinginstallation in explosive gas atmospheres which isdescribed in the main section of this instructionmanual, all BA427E Set Point Stations have ATEXcertification permitting installation in combustibledust atmospheres.
This appendix describes ATEX installations inexplosive dust atmospheres conforming withEN 60079-14 Electrical installations design,selection and erection. When designing systems forinstallation outside the UK the local Code of Practiceshould be consulted.
The Set Point Station’s dust input and output safetyparameters are identical to the gas safetyparameters, so all the electrical circuits shown in themain section of this manual may also be used fordust applications.
A1.1 Zones, and Maximum SurfaceTemperature
The BA427E has been ATEX certified as Group II,Category 1D Ex ia IIIC T80ºC Da IP20 apparatus,Ta -40 to 70°C.
When connected to a suitable system the Set PointStation may be installed in:
Zone 20 explosive atmosphere in the form of acloud of combustible dust in air iscontinuously present, or for longperiods or frequently.
Zone 21 explosive atmosphere in the form of acloud of combustible dust in air islikely to occur occasionally in normaloperation.
Zone 22 explosive atmosphere in the form of acloud of combustible dust in air is notlikely to occur in normal operation, butif it does occur, will only persist for ashort period.
Be used with dust in subdivisions:
IIIA combustible flyings
IIIB non-conductive dust
IIIC conductive dust(For use with IIIC conductive dusts special conditions for safe use apply – see section A1.4)
Having a Minimum Ignition Temperature of:
Dust cloud 120°C
Dust layer on Set Point 155°CStation up to 5mm thick.
Dust layer on Set Point Refer toStation over 5mm thick. EN 60079-14
At an ambient temperature between -40 and +70°C
A1.3 Maintenance
ENSURE PLANT SAFETY BEFORESTARTING MAINTENANCE
Live maintenance is permitted onintrinsically safe equipment installed in ahazardous area, but only certified testequipment shall be used.
The BA427E Set Point Station has IP66 front ofpanel protection and a gasket is provided to seal thejoint between the instrument and the mountingpanel, thus preventing dust ingress from the outsideof the mounting panel. The rear of the instrument isnot sealed as the ATEX dust certification relies onthe internal conformal coating of the instrument.Dust ingress to the rear terminals is acceptableexcept for use in IIIC conductive dusts – see A1.4.However, it is good practice to minimise the amountof dust accumulating on the rear of the instrumentand the terminals.
A1.4 Special conditions for use in IIIC dustsThe BA427E Set Point Station ATEX certificate hasan ‘X’ suffix indicating that special conditions for safeuse are required for installion in IIIC dustatmospheres, the certificate states:
‘For use in Group IIIC conductive dustatmospheres, the Set Point Station shallbe mounted such that the instrumentterminals have at least IP6X protection.’
To prevent the BA427E Set Point Station terminalsbecoming contaminated by conductive dust:
The BA427E must be installed in a panel,cubicle or enclosure providing a minimum ofIP6X protection.
The panel cut-out dimensions must be asshown in Fig 4 and the supplied gasket mustbe used.
Note: These special installation conditions onlyapply for instruments exposed to IIIC conductivedust atmospheres.
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APPENDIX 2IECEx certification
A2.0 The IECEx Certification SchemeIECEx is a global certification scheme for explosionprotected products which aims to harmoniseinternational certification standards. For additionalinformation about the IECEx certification schemeand to view the BEKA associate certificates, pleasevisit www.iecex.com
A2.1 IECEx Certificate of ConformityThe BA427E Set Point Station and the optionalaccessories have been issued with an IECExCertificate of Conformity numberIECExITS12.0084X which specifies the followingcertification codes:
Ex ia IIC T5 GaEx ia IIIC T80ºC Da IP20Ta = -40ºC to 70ºC
The specified gas and dust intrinsic safetyparameters are identical to the ATEX safetyparameters described in this manual.
The IECEx certificate may be downloaded fromwww.beka.co.uk, www.iecex.com or requested fromthe BEKA sales office.
A2.2 InstallationIECEx and ATEX certificates specify identical safetyparameters and installation requirements for bothapprovals as defined by IEC / EN 60079-14. TheATEX gas and dust installation requirementsspecified in section 5 and Appendix 1 of this manualmay therefore be used for IECEx installations, butthe local code of practice should also be consulted.
A2.3 Special conditions for use in IIIC dustsThe IECEx certificate for the BA427E Set PointStation has an ‘X’ suffix indicating that specialconditions for safe use are required for installion inIIIC dust atmospheres, the certificate states:
‘For use in Group IIIC conductive dustatmospheres, the Set Point Station shallbe mounted such that the instrumentterminals have at least IP6X protection.’
To prevent the BA427E Set Point Station terminalsbecoming contaminated by conductive dust:
The BA427E must be installed in a panel,cubicle or enclosure providing a minimum ofIP6X protection.
The panel cut-out dimensions must be asshown in Fig 4 and the supplied gasket mustbe used.
Note: These special installation conditions onlyapply for instruments exposed to IIIC conductivedust atmospheres.