Calibration of I/P (current/Pressure) Honeywell Chapter 8

Calibration of I/P (current/Pressure) Honeywell Chapter 8

Instrumentation ELC-213Today

Presentation by Clifford T. Johnson, PE, Control Systems Engineer

Honeywell Primer: Noise Environments

Honeywell ELC-213

Wire FunctionWire Function

wiring

Honeywell ELC-213

Chapter AC Load Suppression Chapter AC Load Suppression

Suppression

Honeywell ELC-213

AC Contact suppressionAC Contact suppression

Suppression

Honeywell ELC-213

DC SuppressionDC Suppression

Suppression

noise can enter equipment bynoise can enter equipment by

1. Capacitive (or electrostatic)2. Inductive (or magnetic)3. Impedance.

HoneywellNoise ELC-213

Signal cable should always be separated for power cableNever run in the same conduit and

Use dividers in cable tray

Honeywell ELC-213

Prevent Electrical NoisePrevent Electrical Noise

Suppression

There are three ways to prevent electrical noise from interfering with the operation of the electronic digital equipment. • Built-in noise rejection

• Separation of signal and power lines• Noise suppression at source

Ever wonder why Ethernet Cat5 cable is NOT shielded?

ANS: It relies on the BALANCED LINE twisted pair design and differential signaling for noise rejection.

Transducer ELC-213

GroundingGrounding

I/P

Never Grd Shield in the fieldBend back and tape

Operation ELC-213

I/P Principle of operation I/P Principle of operation

I/P

Operation ELC-213

I/P Principle of operation I/P Principle of operation

I/P

Accuracy ELC-213

I/P AccuracyI/P Accuracy

I/P

The accuracy of an I/P transducer is defined in several ways. The most important measure is linearity. This is measured as a percent of span. In this case, the span is 12 (15 minus 3) psig. So if the linearity of the I/P was 1% of span, then the possible variation could be 1% of 12 or 0.12 psig. So in this case, the expected output with a 12mA signal. The output should be 9 psig but could be between 8.88 – 9.12 psig. Linearity can be as low as 0.1% and as high as 3% of span, depending on the construction and cost of the I/P.

Accuracy ELC-213

I/P Repeatability & HysteresisisI/P Repeatability & Hysteresisis

I/P

Repeatability measures the ability of the unit to come back to the same pressure setting after resetting the input signal.

Hysteresisis is the variation in the output pressure achieved when increasing the input signal versus decreasing the input signal. For example, when going from 4 mA to 12mA a certain pressure will be attained. A different output pressure will be achieved when going from 20mA to 12 mA.

Summary ELC-213

Accuracies are additiveAccuracies are additive

Accuracy

Unless specified, these three measurements can be additive. Thus a 3-15 psig unit with +/- 1% linearity, +/- 1% Hysteresisis,+/- 1% repeatability, could be off by +/- 3%, or +/- .36 psig 3% span

Calibration ELC-213

I/P Zero CalibrationI/P Zero Calibration

I/P

Always check the zero setting first. Apply the minimum electrical signal and observe the output pressure. It should be the minimum value of the pressure range. For example, a 4-20mA, 3-15 psig unit should give a 3 psig output at 4mA. If the output is not 3, turn the zero screw until the output pressure reaches 3. The screw may be turned in different directions depending on whether the unit is an I/P or E/P.

Calibration ELC-213

I/P Span CalibrationI/P Span Calibration

I/P

Once the zero has been set, apply the maximum electrical signal, in this case, 20mA. The output should be close to the desired output, in this case 15 psig. Turn the span screw in the appropriate direction to achieve the desired pressure. Some I/P’s have interactive zero and span. In that case, after adjusting the span, the zero will need to be adjusted again, especially if the span was adjusted by a large amount.

Supply ELC-213

I/P Media SupplyI/P Media Supply

I/P

The most common media for I/P’s is compressed air. They can also be used with many other inert gases. However, due to the constant consumption of the media, one must consider the environmental impact of the release of gas into the environment. You should definitely check the specifications before using the I/P with media other than compressed air.

Cal Form ELC-213

Calibration formCalibration form

I/P

Owner:

Tag: System ID:

Description: Plant Location

Manufacture: Calib Location

Model No.: Classification

Instrument Range LRV / URV / Units 0 18 psigCalibration Range LRV / URV / Units 3 15 psig

Accuracy Full Scale/Rg +/- 0.3%. Opt Fail position

Elevation Suppression NA NA

Output Signal Electrical na Pneumatic

% Calib Signal 0% 25% 50% 75%

Calib Signal EU 4 mA 8 mA 12 mA 16 mA

Instr Meas/Out

Instr Required 3 psig 6 psig 9 psig 12 psig

Instr as Found

Instr as Left

As Left error

NA

3-15 psig

20 mA

GP

Calibration data: Suggest using 10, 25, 50, 75, 90 % for 5 points

100%

15 psig

M-Systems

HVPN-2A3

Device to be Calibrated

LY-102

I/P Transducer

CPCC

Cal Lab

Charlotte, NC

ATC Lab

Use your Tag

Analyzer ELC-213

Calibration of AnalyzersCalibration of Analyzers

pH

pH is one of the most difficult

Analyzers to calibrate

because the measurement

is log

Assignment ELC-213

Homework ASSIGNMENT Web LinkHomework ASSIGNMENT Web LinkFind instructions on Internet for PID Control Modes.

email web page LINK only to me by Sunday

Email Ex:Email Ex: Johnson-PID Modes- Johnson-PID Modes-AD

All Emails Subjects and File names must haveAll Emails Subjects and File names must have

You will lose 1-3 points for incorrect subject

Subjects

SubjectSubject::Your last Name-Subject-Assignment Date (AD)

Calibration ELC-213

The EndThe End

End

M-Systems I/P you will

be calibrating