For electrical engineers only: I have a pressure transmitter...?
Anyway i made sure that there is no ground loop so i grounded the shiled at only one terminal
So what causes this jump?
Answer:
Sorry, but I can only come up with more questions!
Is this a fault which has appeared on an existing system or is it a new installation?
How long does the 'jump' last? Is it a transient effect, or present all the time the motor is running?
Is the power supply for the instrumentation derived from the same source as the supply to the motor? e.g. at the far end of a long supply cable.
Clearly there is an unintended coupling somewhere. Do you still get the effect if you temporarily power the transmitter from a battery?
does the pressure increase briefly when the motor kicks on?
Has the transmitter been calibrated? That is zero, or 4 mA, and 20 mA at full pressure? If this calibration has not been done then it's response is not reliable. Your 8 mA is about 25% of system pressure, assuming proper calibration of the loop, and transmitter. 25% of rated pressure isn't bad, unless you are looking for the system to remain at zero until a working fluid is introduced into the system. Off hand, I would say that the system is operating as it should since it is a pressure transmitter, which is doing what it was designed to do, measure pressure. One quick question, is the transmitter located beyond the outlet of the pump? If so, then the jump is pressure surge from the pump and is normal. What is needed if the transmitter output is to remain at zero would be either an orifice plate to isolate the transmitter, or a differential transmitter that is adjusted to not respond to that pressure spike. Ask the manufacturer of the transmitter for technical assistance. I am sure they have engineers that can help you.
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: