AI810 module channel value fluctuating at higher ranges
I observed a strange phenomena in AI810 Io modules. The channel values work perfectly fine when the channel maximum range is low. When we increase the max range to a higher value (for eg: 0-30000) the channel value fluctuates a lot. I am testing this in my lab by forcing the current from a mA source. The results were similar even when I looped the output of AO810 to the input of AI810 to eliminate any errors in the mA source. Can anyone explain the reason for this behaviour?
Thanks in advance.
I think you should take in consideration the fluctuations in % of the range defined.
In the tech. specification of AI810 the max. error is given = 0,1%.
In case you have a range 0-30000 then the fluctuation will be 30 units.
In case you have a range 0-300 then the fluctuation will be 0.3 units
What fluctuations you are observed during your tests ?
It's not a strange error when you try to feed mA across high range value of a channel off course there is a small diff will be there in your card channel level, you please doubt even on loop calibrator which is calibrated properly or not since few tiny current can cause some surge in your measure value as well.
Even myself also observed this small decrease or increase in the value across any points of the feeded mA.
Generally cards A/D are calibrated to read d precise values.
Indeed as mentioned by other Seniors, Analog Input fluctuates always,despite of exact stable INTEGER count.
I used to think this thing, and later worked on a Textile Industry with PLC 500.
There I read the 0-10 V , and 0-20mA both inputs live on Codesys.
It shows me that count varies for a value of +/- 40 or 50.