4-20mA convert to V input on MC43 using 250ohm resistor

Kevin 2 years ago in Master modules / MC4x updated by anonymous 2 years ago 2

When using a high precision 250 or 120ohm resistor to allow IQAN to measure the signal from a current loop, do I need to connect Vref -VE for ground reference?

Image 3288

You would connect the sense resistor between the output of the 4-20 mA sensor, the module voltage input and module ground. Like this:

You could use either -VREF or -BAT. 

Using -VREF might reduce the risk of having measurement errors due to ground difference. 

Using -BAT might reduce the risk of module damage if there is a short across the sensor and the sense resistor. 

Thanks, I think this will not work for us however. We don't intend on using a 4-20mA sensor that we convert to voltage, rather we want to intercept a 4-20mA signal already in a different controller and sense the value in our IQAN IOT. The customer has a existing system we know not much about only that it is a different manufacture.

We have two separate systems, one is a different manufacture with a 2 wire current loop (existing system), and the second system is IQAN telematics. We intend on taking signals from the current loop on the existing system, and feeding voltage signals into an MC43 VIN. Using the first method (in image above) we insert a 250 ohm resistor within the current loop and take a signal however IQAN needs the reference voltage to 'see' the value.

Can you recommend another way of connecting?