DAQ Board Replacement

[ckramer]

I was assigned to a project to alter one of our existing data acquisition systems due to a vendor supply issue with the DAQ Board.

Here is what we need to do: change our current DAQ Board that reads 3 analog signals on a 0-10V Unipolar scale to a DAQ Board that uses a Bipolar -5V to +5V scale.

The signal conditioner is a single module with 3 input channels, it is somewhat unique to our application since it has an "AutoZeroing" feature built-in which stabilizes (pulls the voltage back to 0) on all three signals when a relay is turned on. This conditioning unit is only available in a 0-10V configuration and we have to keep it in the current design.

I need to know if there is any device or method we can use to translate the 0-10V signal coming from the conditioner to a -5 to +5V signal into the new DAQ.

Every resource I've tapped into on this subject said the signal conditioner will have to change or we'll have to come up with a custom circuit board to translate the voltage. If any further specifications, code, or information is required please let me know - I will be happy to provide it.

Thank you,

Chad

 

[MikeHalloran]

Run the signal conditioner on +/-5.
I.e., arrange it so that everything the conditioner thinks is ground, is really a phony ground tied to -5V. And similarly, arrange it so that everything the conditioner thinks is +10V, is really +5V. That will probably require some kind of roached on circuit board, or a redesign of the one you've got.

You will probably have to translate the relay input, also, perhaps with a second relay.





Mike Halloran
Pembroke Pines, FL, USA

 

[ckramer]

Thanks for the idea Mike.

I was able to get more information from the signal conditioner manufacturer on their configuration, they said it could be possible to shift the 0V on all three channels by turning the Zero pot until a -5V value is found. The high end of the scale will follow and become +5V. The drawback is when the AutoZeroing feature is turned ON it will attempt to sink or source to the true 0V - right in the middle.

The circuitry for the signal conditioner is proprietary and they will not release a schematic for the board components. So we don't have any chance to customize it as needed.

We will have to find a method via the code to compensate for any zero shift, heating elements are used in this application and greatly affect the stability of the load cells.

Thanks again,

Chad