How to read a 4-20mA weight transmitter with Arduino?

Other Hardware Device Hacking
1

Dear All,

510-WeightTransmitter
510-WeightTransmitter758×564 69.9 KB

I am trying to get weight value from a 4-20mA 510 weight transmitter with no luck.
The Load Cell is correctly connected to weight transmitter, and also calibrated transmitter's accuracy totally following https://www.youtube.com/watch?v=o3bVCWKPT0s ,

My question is:
How to wire "Output I/P-/V" of the weight transmitter to Uno? and how to read the weight?

Any guide or example will be great appreciated!
Thank you so much!

David

2

The simplest option is to pass the 4-20 mA output (I suspect you use the I and P- outputs) through a 250 Ohm resistor, and read the voltage (1 to 5V) with the ADC. P- must share ground with the Arduino ADC.

The next simplest option is to buy a current loop receiver that is compatible with Arduino.

Search for "Arduino read 4-20 mA sensor" for more options.

3

Thanks for getting back to me so quick.

Yes, I use I and P-.
Power is 24DCV, no resistor in-between I and P-, it shows 4mA when 0 gram, and 4.32mA when 2000 gram on Load Cell, and voltage is always 13.98V.

I don't know much of electronic engineering, cannot figure out their relationships.
Could you please show me the correct wiring diagram for Arduino?

Thank you!

4

I searched for "Arduino read 4-20 mA sensor" and found this diagram, on this forum.

You could too!

5

Hi, jremington

Thank you so much!
I'll try it ASAP.

David

6

@davidleetw - a word of warning. In the circuit shown, if you ever, even for a second, disconnect the 250 ohm resistor while the 24V is present and connected to the analog input, you will destroy the analog input of the Arduino, at minimum. This is one of the prime failure modes of 4-20 ma signaling; proper work practices must always, always, always power down the 24V loop, AND wait for that power supply to discharge, before messing with the resistor.
I mention this because it's common to put the resistor on a protoboard, and route the signal to the resistor, then to the AI; this sets the user up to a situation where the resistor can easily be removed without disturbing the rest of the circuit, and presto, AI toast.

1 Like
7

Thank you for your information!

8

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.