I have to read 4-20 mA output from six water pressure transmitters and six water flow sensors. As, in case of flow sensors (sink type) this mA output is not flowing towards ground, I cannot just drop the current in a 250 ohm resister and measure the voltage (1-5 v) across it in respect of ground.
I made the attached circuit and when tested individually (either only PT or only FS) it gives linear and correct output voltage at Op-AMP (OP 07) o/p (with 24v GND and 9v GND isolated). But whenever I tried to use the both (PT and FS), the digital displays showed erroneous results.
What may be the reason and how to recover it?
I made the attached circuit and when tested individually (either only PT or only FS) it gives linear and correct output voltage at Op-AMP (OP 07) o/p (with 24v GND and 9v GND isolated). But whenever I tried to use the both (PT and FS), the digital displays showed erroneous results.
What may be the reason and how to recover it?
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