Calibration of I/P (current/Pressure) Honeywell Chapter 8 InstrumentationELC-213Today Presentation by Clifford T. Johnson, PE, Control Systems Engineer Honeywell Primer: Noise Environments

HoneywellELC-213 Wire Function wiring

HoneywellELC-213 Chapter AC Load Suppression Suppression

HoneywellELC-213 AC Contact suppression Suppression

HoneywellELC-213 DC Suppression Suppression

noise can enter equipment by 1. Capacitive (or electrostatic) 2. Inductive (or magnetic) 3. Impedance. HoneywellNoiseELC-213 Signal cable should always be separated for power cable Never run in the same conduit and Use dividers in cable tray

HoneywellELC-213 Prevent 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.

TransducerELC-213 Grounding I/P Never Grd Shield in the field Bend back and tape

OperationELC-213 I/P Principle of operation I/P

OperationELC-213 I/P Principle of operation I/P

AccuracyELC-213 I/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.

AccuracyELC-213 I/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.

SummaryELC-213 Accuracies 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

CalibrationELC-213 I/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.

CalibrationELC-213 I/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.

SupplyELC-213 I/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 FormELC-213 Calibration form I/P Use your Tag

AnalyzerELC-213 Calibration of Analyzers pH pH is one of the most difficult Analyzers to calibrate because the measurement is log

AssignmentELC-213 Homework ASSIGNMENT Web Link Find instructions on Internet for PID Control Modes. web page LINK only to me by Sunday Ex: Johnson-PID Modes- Ex: Johnson-PID Modes- AD All s Subjects and File names must have You will lose 1-3 points for incorrect subject Subjects Subject : Subject :Your last Name-Subject-Assignment Date (AD)

CalibrationELC-213 The End End M-Systems I/P you will be calibrating