Crazy Analog Output...

[Bluenoser337]

Modiccn Compact DAU-204 Analog Output card configured for 4-20mA. Everything is configured correctly (switches and software), but the outputs are acting weird. Raw value is 0-4095 which should correspond to 4-20mA but the output signal (on at least 2 of the channels (didn't test the other 2)) is not linear and is not proportional to the raw output value. 0 raw gives 3.82 mA....that I can live with, but 409 gives a 1.93 mA output, 2047 gives .99 mA, 2866 gives 13.16, but 3685 gives 2.03 mA. I think the card must be bad but wondering if anyone has ever encountered this? The device being controlled is not causing the problem...connected mA meter and calibration device directly. Thanks!

 

[roydm]

Is this a new problem with existing hardware or are you commissioning a new system? I seem to recall having a similar problem that turned out to be a configuration error.
It almost seems like the D/A is not responding to the more significant bits e.g as you go from 0111-- to 1000-- it's not seeing the MSbit. Either that or the module is getting some value you don't see in decimal format.
I suggest you look at the output word in bit format, you might see something there, try turning on one bit at the time.
Roy

 

[Bluenoser337]

Hi Roy....it's a 10 year old system that has been out of use for a few years. Not at the site now, or I'd try the one bit thing. I agree about the D/A thing. Trying to get a replacement card to try, as well. Thanks!! B

 

[roydm]

I just had a look at an old file, there is a 30xxx register associated with the module, I think thats status.
Check bits 12 thru 15 of the 40xxx they should all be 0
It's also strange that zero gives you less than 4 mA. I wonder if one of the electrolytic capacitors has failed du to being powered down for a long period.
If you do an upload of the program you will be able to look at the register values off site.
Good Luck
Roy

 

[itsmoked]

Never hurts to check AC current if you are seeing strange results on a DC system. You can get really weird readings from it.

Keith Cress
kcress -

http://www.flaminsystems.com