Question on the industrial automation card for Rasberry Pi. From the factory I was reading values 3.94 -13.3 in node red when driving the input using a signal generator. I used the same signal generator to calibrate one of the 4-20mA inputs.
I ran the calibration command at at 4mA and at 20mA using this process:
set generator to 4mA run command megaind 1 iincal 2 4
set generator to 20mA run command megaind 1 iincal 2 20
After running the calibration I used the signal generator stepped the signal up by 25% steps and monitored the values received in node-red. Here are my results:
4mA - 4.011 in node red
8mA - 10.719
12mA- 17.289
16mA - 19.913
20mA- 20.05
Why is the scaling off between 4 and 20 but accurate at the ends?
I ran the calibration command at at 4mA and at 20mA using this process:
set generator to 4mA run command megaind 1 iincal 2 4
set generator to 20mA run command megaind 1 iincal 2 20
After running the calibration I used the signal generator stepped the signal up by 25% steps and monitored the values received in node-red. Here are my results:
4mA - 4.011 in node red
8mA - 10.719
12mA- 17.289
16mA - 19.913
20mA- 20.05
Why is the scaling off between 4 and 20 but accurate at the ends?