NI 9265 Compliance Voltage

[kent.wedeking]

Can anyone give me a decent reason why the compliance voltage on the NI 9265 is only 12V, but you can supply the card with 9-36VDC?  The process control industry would REALLY love to know if there is any chance of updating this someday.

[JÞB]

The compliance voltage is 12V because the output load is rated to a max 600 ohms.

I would assume this is set with respect to the characteristics of the DC-DC converter and finding one with clean enough regulation to support a 16bit ADC so that sub-microAmp precision is achievable.  But I had no hand in the design considerations.

[kent.wedeking]

Jeff, that all makes absolute sense, and I'm sure those were the considerations.  tradeoffs have to be made.  I just happen to know some fairly large companies, and a few small ones (Iike JET) that are finding this to be an issue.  I'm having issues powering a valve via 9265 and being able to use a HART modem with it, and I'm not the only person.

[JÞB · Accepted solution]

That may be an issue for the Idea exchange.  I could see where trying to power multiple devices from a single loop could require a higher compliance voltage.  

The distributed system you allude to does seem like an interesting challenge.  

[kent.wedeking]

Thanks Jeff!  Yes, a challenge would be one way to describe it.  I think its about to get a push on it from a lot of us around about August time 😉