At a machine is a pressure sensor 4-20mA powered with 24V
and a SPS which reads the current of the sensor, so we have
to share the signal.
The goal is to integrate the AD4112 in the current loop.
Because of the 24V supply in the loop we cannot connect IINx- to GND.
Is it possible to use IINx+ and IINx- as a differential pair?
Unfortunately the EVAL-AD4112SDZ connects all IINx- directly to GND,
so we cannot test the AD4112 with this evaluation board in our environment.
Thank you for your help.
Yes on the evaluation board these pins are directly connected as this is intended to be connected to GND for return path current input (-0.5mA to +24mA). But it is possible to use this as differential or biased the IINx- at some point to lower the current across 50ohm, please take note of the Absolute Input Voltage specification for current pins which is: AVSS-0.05 to AVDD+0.05. The voltage on Iin+ or Iin- should not exceed these limits. You have mentioned that you cannot connect IINx- to GND, can you explain further why and if you could share us the schematic, it would be great. May I know also what is an SPS?
Thank you for a quick answer.
In your language it's called PLC (Programmable Logic Controller), i.e. Beckhoff, Siemens, etc..
In this case there is no chance to connect at the low-side of the loop because it's happened in the SPS itself.
We have to chain at the high-side. The current loop is powered with 24V,
but the voltage at the shunt resistor would be less than 1.2V, which will meet the maximum input voltage of AD4112.
(Total impedance is 5+50+5 Ohm for AD4112, not just 50 Ohm)
Thank you for your help,