© 2007 ideal industries 1 of 26 basics of meter safety

Basics of Meter Safety© 2007 Ideal Industries www.idealindustries.com 1 of 26

Basics of Meter Safety


Digital Multimeter Safety


Ideal Test and Measurement

• Goal– Awareness of the potential

Measurement Hazards– Learn How to minimize and

avoid Electrical measurement hazards

– Understanding of UL61010 (IEC 601010)

• Over-Voltage Categories

Safety Practices with Electrical Testers


Why should we be Concerned?

• An electrician troubleshooting a live 480V motor control center receives serious second- and third-degree burns from an electric arc. The cause? – Meter was incorrectly

switched on his multimeter to read resistance instead of voltage.



• Two electricians are severely burned — one fatally — while testing for voltage in a motor starter. One held the multimeter while the other applied the meter's probes to energized terminals. One electrician's movement caused one test lead banana plug (energized from the circuit under test) to pull loose from the multimeter jack. – The plug made contact with

the starter's grounded metal enclosure and initiated a high-energy arc.



• An electrician is sent spiraling from a steel tower while checking a circuit with a multimeter. He was using a meter rated for 1000V to verify a 15kV circuit believed dead. He didn't know the circuit was hot. Therefore, when he applied the multimeter, a phase-to-ground

fault occurred. – Fortunately, his safety

harness stopped his fall and coworkers on the ground rescued him.


Common Mistakes Made

• Test Leads in the Current input ports and user mistakenly makes an AC or DC Voltage– In this example there were two

errors made by the end user.• AC voltage measurement

with the Test leads in the current input.

• Improper fuse had been used in the meter from a past error.



• Make sure not to exceed the Max input of your meter.– Most common mistake is to

measure voltage with the leads in the current inputs.

– Current inputs are very low resistance. It appears as a short circuit to Voltage.

– For current input protection most DMMs’ are Fused.

– Look for high energy fusing.

Current

Protection

Fuse

Current Measurements with Meters

Ideal 61-490 series give a probe error message and High audible warning if

this mistake is made.



• Function Switch in wrong function for attempted measurement– Example: AC or DC voltage

measurement with function switch in Ohms.

– Most Ideal meters are Overload Protected and the protected levels are listed in the operation

manual. Ideal 61-700 series will

give you a Hi-V and audible warning if you

make this Mistake



• Using a meter in an area above its stated rating – Example: 2,300 voltage

measurement with an instrument rated for Low Voltage (600V AC/DC.)

– Overload Protected can not protect you from this Kind of mistake.

– Most Overload protected is rated based on instruments highest voltage measurement rating.

There are Bold Electricians and Old electricians, but not many

Bold-Old ones


Common Safety Hazards

• High Voltage transients from lightning, large inductive loads being switched on and off, or capacitive discharge. – Select meter with the proper

UL/IEC Category rating for the environment that user is going to be working in.


Safety Practices

• Visually inspect the test tool.– Check for any contaminate on the test

leads, tester case, holsters, and accessories.

– Never use testers that have signs of cracked cases, or loose components.

– Never use a tester in an environment that is beyond the capabilities described in the specifications

– Use manufactures recommended replacement components, like leads and fuses.


Safety Practices

• Visually inspect Test Leads– Proper Category rating

– Double insulation

– Shrouded connectors

– Finger guards

– Insulation not damaged: not melted, cut, cracked, stretched

– Connectors: no insulation pulled away from end connectors

– Probe tips: not loose or broken off (too short)


Before you get Started

• Quick Check of your Test Tool– Digital Multimeter or Digital Clamp meter– Check the Test Leads– Place the DMM in the lowest resistance range and short the Test Leads– Move the test lead at in input of the meter at the ankle of the leads. Watch that

the resistance is less than 0.5 ohms. Do the same at the leads grip and tips. If at any time during this test the resistance exceeds 0.5 ohms the leads my need to be replaced.

• It is also a good Idea to check the DC voltage and Ac voltage with a known source before beginning the day.

– This doesn't negate the “Three point measurement” method.

• If the unit has current, check the Fuse, and remember to replace with only the manufacturer recommended replacement part.

• Remember to always be aware of your battery usage. Digital instruments will become erratic or can give improper readings once the power drops below normal operating levels


Before you get Started

• Whenever possible, work on de-energized circuits. • Use well maintained tools and appropriate safety gear

– Follow New NFPA 70E Guidelines• Safety glasses, insulated tools, insulating gloves,

flash suits, insulating mats, etc.

• Follow proper safety precautions and Lockout Tag out practices.

• Never Work alone when making measurements on live circuits.

• Always do a performance test on your tester before making a measurement on an unknown circuit.

– Use the 3 point method. Measure a known test point , Make the unknown measurement, then back to the known test measurement.

– Change battery when indicated – Check test leads regularly


Know your tester

• Packaging– Material,

• Insulation rating• Environmental rating,

Splash proof or not.• Features

– MIN/MAX, Peak, Hold• Measurement Functions

– AC Volts, DC Volts Capacitance, etc

– Measurement range and Maximum input

– Input protection.• Safety

– CATegory rating, UL, CE


Certified Devices and Equipment

• Look for tools that are Certificated by an independent lab,

– UL , IEC, CSA.• Pay close attention to the safety

rating on the equipment.

– Never use equipment that is not properly rated

• Never use accessories that are not recommended or rated for your tester or environment.

IEC Cat ratingsThe New UL 61010B standard

incorporates features of the IEC 601010 standard. This standard

has improved safety benefits over the old UL 1244 standard


IEC Category Ratings

• IEC 61010 defines as four Categories:– CAT IV “Origin of

installation”,

– CAT III Distribution Level,

– CAT II Local level,

– CAT I Signal Level,

If a lighting strike was to hit your electrical service a certain amount of energy or impulse would travel and be dissipated by the electrical service.

The closer to the source of the impulse the Higher available fault current.


International Electro-technical Commission

• IEC 61010 requires an instrument provide protection against “over-voltage impulse transients” - voltage spikes.

• IEC 61010 is the basis for:

– ANSI/ISA-S82.01-94 (US)

– CAN C22.2 No. 1010.1-92 (CAN)

– EN61010-1:1993 (EUR)

• UL 61010B standard incorporates features of the IEC 601010 standard,

– This standard has improved safety benefits over the old UL 1244 standard and the old IEC 348


Impulse Fault

– The closer to the source of the impulse the Higher available fault current.

– If an instrument was to be hit by an impulse and a fault condition was to occur the Available energy “Fuel” the Fault.

– Lets use the example of water or water pressure.– The larger the pipe the Greater the potential– The closer to the supply the Greater the potential

Fireman with a 4 inch

hose

Faucet with ½ inch

supply line


Category rating, Voltage mean What

CAT III-600V or CAT II-1000V?

The greater the source impedance,the lower the Category:

• CAT III-600V:– 6 kV impulse – 2 Ohm test source

• CAT II-1000V:– 6 kV impulse – 12 Ohm test sourceA CAT III-600V 6kV test impulse

has 6 times the current of a CAT II-1000V 6kV test impulse!

• Voltage rating by itself can be misleading.– CAT III-1000V (8kV

transient) is safer than CAT III-600V (6kV transient)

– But CAT III-600V is safer than CAT II-1000V


CAT IV

• Outside and service entrance

• Service drop from pole to building

• Run between meter and panel

• Overhead line to detached building

• Underground line to well pump

Equipment of over-voltage category IV is for use at the origin of the installation (utility service).


CAT III

• Permanently installed loads: motors, lighting systems, drives, load centers.

• Typically separated from utility service by at least a single level of transformer isolation.

• Does not include receptacle plug-in loads, except in the case of heavy appliance outlets with “short” connections to service entrance

Category III is Premises wiring: “mains”circuits, i.e., bus and feeders and distribution panels


CAT II

• Examples of such equipment are appliances, portable tools and other household and similar loads

• All outlets at more than 10 m (30 ft) from Category III

• All outlets at more than 20 m (60 ft) from Category IV

Category II: Loads that plug in at receptacle outlet


CAT I

• Examples are protected electronic circuits. A copier that has an internal step-up transformer and 1000Vdc is still a CAT I-1000V machine, because the current levels are so low.

Equipment in which measures are taken to limit transient over-voltages to an appropriately low level.


Thank you

You may want to refer to the Following PapersCase histories come from an IEEE paper entitled “Personnel Safety

and Plant Reliability Considerations in the Selection and Use of Voltage Test Instruments,” (IEEE Transactions on Industry Applications, Vol. 33, No. 2, March/April 1997),written by H. Landis Floyd II and Brian J. Nenninger.

• ANSI C62.41 - IEEE Recommended Practice on Surge Voltages• IEC 601010• UL 3111• Part II NFPA Code 70E

Ideal Industries, IncTest and Measurement Division

1 Becker PlaceSycamore, Il 60178

(800) 435-0705

© 2007 ideal industries 1 of 26 basics of meter safety

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