0
Answered

Voltage inputs automatically offset by VREF supply?

Kevin Arscott 3 years ago updated by Gustav Widén (System support) 3 years ago 2

We are using ratiometric voltage sensors for an application, by selecting the reference voltage (A or B) on the controller input, does this automatically offset the VIN with the VREF supply fluctuations?


We know that because the sensors are ratiometric the supply to the sensor will cause the signal emitted from the sensor to change slightly. We have achieved this using code in the application, however i'm just checking the controller does not compensate for this automatically without the need for user configured code? I would imagine it does not do it automatically because there is no option to select its a ratiometric or normal regulated sensor connected to the VIN.


Perhaps this could be a feature we see in a future IQAN Design? I know we would find it useful instead of having separate code. Provided of course the variation % on a ratiometric sensor output is the same for different manufactures of sensor, if they are different, maybe an option to enter some values?

The selection of VREF-A, VREF-B or None on the VIN property for VREF is used in case there is a VREF error. 

The VIN:s are automatically assigned error value and the status VREF error if its associated VREF has an error on it. 



When you use the module VREF to supply a radiometric sensor, errors in absolute accuracy of the reference voltage is cancelled out. It is not a software function, it is just an effect of using the same 5 V reference for the VREF supply as for the AD conversion. 

That is why you on in the Appendix A information on the VIN:s can read that the absolute accuracy differs between using the module VREF and an external reference.