Questions about temperature and humidity transmitters
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I have a temperature and humidity transmitter here; the output signal from the transmitter is fine, but once it is connected to the DCS cabinet, the signal disappears. What could be the reason?
Do the signal types match? Active/passive, voltage/current… etc
The temperature and humidity transmitter is a four-wire type: power +, power -, temperature output, and humidity output – four wires in total. The negative terminals for the temperature and humidity outputs share the same connection as the power negative terminal.
This post was last edited by tiger2010 on 2020-10-13 at 13:01. This is called a three-wire system. Some meters using this system come with shorting terminals to select between active and passive modes, while others do not have such terminals; it depends on the specifications of your specific temperature and humidity transmitter
The problem was resolved: the transmitter is active, and the terminals in the DCS cabinet are also active, which caused a conflict. Later, the terminals in the DCS cabinet were changed to passive ones, the software was modified as well, and the short-circuited pins on the PCB boards inside the cabinet were adjusted as well; thereafter, the display on the DCS monitor started to show proper information.
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