Lost In Calibration Land: A DP Transmitter How-To Story

When you are faced with DP transmitter calibration, do you call in a specialist, or do you try to do it yourself? Most analog DP transmitters are easy enough to calibrate on your own. Of course, if you are not sure if you are doing it right, it may still seem complicated, even with excellent directions. Here is how most people like yourself get lost in transmitter calibration land, and how you can make it out on your own.

Determine If Your Transmitter Is an Analog or "Smart" Transmitter

An analog transmitter would be easier to understand and calibrate than a "smart" transmitter. Ergo, it helps to take the first step out of this situation by finding out what kind of DP transmitter you have. If you have a "smart" transmitter, leave it alone and walk away. You practically need an IT degree to do anything with that! If you have an analog one, get out your trusty screwdriver set and get ready to calibrate.

Find Your ZERO and RANGE/SPAN Screws

These screws should be clearly marked on the outside of the transmitter. Once you find them, take the screwdriver that fits these screws and turn them until the ZERO screw reflects at zero on the measuring gauge. The RANGE or SPAN screw needs to be adjusted for one hundred, on the nose. It should not be slightly less or slightly more than one hundred; the gauge needle should be right on one hundred, period.

Turn the Transmitter on and Check for Accurate Readings

Now, turn your analog DP transmitter back on and check the readings. When the transmitter is functioning properly, the readout will reflect correct transmission waves based off of known widths. A very, very tiny percentage to be off the mark is allowed, since transmission waves have their own quirky fluctuations. If the known measurement is appearing off by too much, you will need to turn the transmitter off and continue to adjust the screws for ZERO and RANGE/SPAN.

Getting It Right

Once the calibration has completely hit the mark and it is spot on, you can put away your screwdrivers and go home for the night. Be sure to check the transmitter again the next day to make sure it is still on target. It should be, unless someone else comes in on the shift following yours and messes with the transmitter. If it is suddenly off and no one else has touched the transmitter, seek professional help, such as from Cooper Controls Inc.