NI-9472 and Vsup, overvoltage and output forced high

[stinf]

Hello,

I am bout to buy an NI-9472 module. I will use it with a 24 V DC power supply in order to control a few relays.

I see that the module has a 30 VDC safety voltage on I/O pins, but what if power to cDAQ is turned off when Vsup is still on? Does the module get damaged or can it whitstand those 24 V DC even when turned off?

A second question: can I use a button in parallel to an NI-9472 output in order to force that line high (at 24 V) even when the module is requested to keep the pin low? In other words, what happens if I try to force a pin high in hardware, when software (Labview) tells it to keep low?

Thanks in advance for your help.

Stefano

[santo_13 · Accepted solution]

Given there is no explicit detail of how the protection differs between powered and unpowered, I assume both are the same.

For your second question, 9472 is sourcing output module, this means, it can only source a voltage and not sink it, in other terms it cannot pull the output low, so, connecting a switch to override the load should not affect it as it would not attempt to sink any current within the protected voltage range.

[stinf]

Hi santo_13, thanks for your help!