Q. I have a pressure transmitter that outputs a 4-20 mA signal over a 0-100 psig span. Occasionally the pressure goes slightly below or above the transmitters range causing the signal to go as low as 2 mA or as high as 22 mA. This is causing problems with my BAS controller because that particular point is programmed for a 4-20 mA
input. What can I do?

A. Kele offers a product, the UMM Universal Math Module, which has high and low limit control. The UMM can be calibrated so that it will output a 4 mA signal any time the input signal is 4 mA or less and to output a 20 mA signal any time the input signal is 20 mA or greater. The signal remains linear within the 4-20 mA range.