Problem in PCB122C100 reading 4-20mA sensor

[Joze]

Hello we are using PCB122C100 and MPS052A100 and are trying to read analog data and have some problems, we receive “1.#QNAN” as a result (See screenshot). Have you any idea ?

[Sergio Bertana]

The problem is the acquiring mode (FB input Mode), in the PCB122 firmware previous of SFW170C100, the mode 13 was not managed.

Solution, you can use the mode 06 Current from 0 to 20 mA (Differential mode) and subctract the 4 mA by software, or you can upgrade the module firmware (Please refer to FAQ).

[Joze]

Ok, we figured it out, the analog sensor wasn’t correctly wired: + goes to 24VDC power supply, while – goes to the analog input e.g. AI01, then the resistor is placed between AI01 and AI02 and then you bridge AI02 and AGnD – this is for current differential connection. Works now nicely.

[Autore]

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