Issues with the 3051 pressure transmitter module
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The range of the pressure gauge is -40 to +40 kPa. The control room indicated a reading of -1.3, but upon on-site inspection, there were no issues with the zero point or the range. When the gauge was used in the field, it showed a reading of 2.5 kPa; checking the wires in the intermediate junction box also revealed no problems, and the current measured was 11.81 mA. The problem was identified: it is normal for the gauge to show a negative value when the current is below 12 mA. It was determined that there was a fault in the transmitter module, and replacing it with a spare module resolved the issue. So why, before replacing the module, did I measure the current when the transmitter was connected to the atmosphere, and it was 11.5 mA? At that time, the gauge’s pointer was already at zero! What I want to know is what role the 3051 transmitter module plays in this case, and why there are problems; why does this current value still experience relative changes between when it is in use and when it is not? I hope an experienced master can come to teach me and answer my questions. Thank you
To be honest, after you said so much, I didn’t quite understand. Do you mean that, in the case of the atmosphere, the instrument returns to zero, but the output current is not 12? Later you said it’s normal for a negative value to appear when the number is less than 12, and I didn’t understand that either. It’s probably a problem with the output module – you’re referring to that entire display module, right? It’s the one responsible for output, and it’s having issues. You can use Emerson’s 475 to reset it to factory settings, and then try performing a current calibration to see if it can be fixed
Yes, I’m talking about the module that is integrated with the display screen. What I mean is that as atmospheric pressure changes, the current value I measure also changes accordingly. If there’s a problem with the module, how can its output current still change? Moreover, this change is proportional to the change in pressure
Your understanding is that if the module is damaged, the output current should remain constant at a certain value, rather than changing with pressure as it does now? And the trend of change is roughly the same as well?
Based on the owner’s description, it is necessary to first calibrate the transmitter for zero point and range. A reading of 11.5 mA for atmospheric measurements is normal; it is the transmitter’s zero point that has drifted and needs to be calibrated.
OP, is the current value you measured the one displayed on the screen, or the one read by the handheld controller?
It’s the current value I measured at the intermediate junction box
There are no issues with either the zero point or the range; I’ve checked them both
Check the zero point and range, and apply a certain pressure to observe the stability over some time
The zero point and range are definitely fine… When pressure of around 2.5 kPa is applied to the gauge, the current remains in the 11.8 range
I have encountered this situation before. The gauge head shows the actual pressure; there is no problem with the piezoelectric conversion part, as the gauge head displays the value accurately. But the current output section must be broken. I used Honeywell transmitters before. It is divided into a pressure sensor, a piezoelectric conversion module, a digital display module, and an output module. The output module has been replaced several times. Some were damaged due to water intrusion, while others were damaged from natural aging.