How ot connect NI PCI-6723 to get +-20V.

[kei_wata]

I have PXI-6723, 32ch analog output module.A specification sheet says that channel to channel connection provides +-20V.I want to know how to connect channel to channel to obtain +-20V.Actually, If I set AO1(Ch.1) -10V and AO2(Ch.2) +10V, we can get voltage difference of 20V. (AO2 is 20 volt higher than AO1.)

However, in this case, AO1 is not the same as the GND level which has other instruments which use in a measurement.

It is problem for my measurment.

Can I connect AO1 to GND which has other instrument has?As a similar question, can I connect external voltage to AO GND?PXI-6723 can control +10 to -10V.For example, by using an external DC supply, can I control -20 to -30V.If I can connect an external DC supply which set -20V to AO GND, can PXI-6723 control up to -30V?Please tell me some information to how to connect channel to channel to obtain +-20V range.

(espectally, I want to get from 0 to -20V.)

[Michiel_H]

Hi kei_wata

Where exactly did you find the information on the channel to channel connection? The only thing I could find in the specs are the maximum channel to channel working voltages. These are +- 22V Channel to channel and do not mean that you can interconnect several channels to reach a voltage of 20V. What they actually mean is that the maximum voltage difference there can exist between two channels to not damage the board is 22V. As your card is not isolated, the ground of the card in the end leads to the computers chassis ground, so it won't be a very good idea to provide the -10V to the ground of another device, as it may lead to weird situations.

The only situation when you could do this, is when you connect a floating instrument (e.g. a normal resistor which has no other connection to the GND) to the -10V, to achieve a 20V total accross the resistor.

So in general, you can only achieve a +-10V output per channel. If your device is floating however, you could combine 2 analog outputs to form a 20V difference accros the connected device.