Problems with TBX-68T IEX1

[Rita V.]

Hello,

I'm a beginner at working with NI 4351 board with TBX-68T. So, there is two current outputs: IEX0 (25 uA) and IEX1 (1 mA). I need to measure temperature useing thermistors and those two channels at one time. But I have a problem: while IEX0 is working (it has ON/OFF switch), IEX1 doesn't. I mean, I have no current from it (it should be warking all the time?). Maybe someone knows where's the problem?  

Thank you very much. 

[tnek]

Hi Rita,

I was wondering if you could clarify your question a bit. Are you trying to use both current sources at the same time or do you just need to read from multiple thermistors? A good connection diagram can be found on page 2-18 and 2-19 of the NI 435x Users Manual if you need to connect multiple sensors. In addition, IEX1 does not have a switch and should be able to supply the 1mA current as long as the you connect the thermistors to this current source. You can also specify which current source to use in the NI-435x API using the NI435X Set Current Source function.

Regards,

Kent

Applications Engineer

[Rita V.]

Hello tnek,

well, I need to read from a few termistors. And I have a scheme, how to do it, but the problem is, that IEX1 doesn't work. And I am wandering why it doesn't work. As IEX0 is working but for that multiple connection that I know, IEX0 with 25 uA can't be used and I need IEX1 with 1 mA. So, I just want to know how to test TBX-68T IEX1 connection.

And please, tell me more about using the NI435X Set Current Source function to specify which current source to use.

Sorry again for the stupid questions, but I'm just a beginer...

[tnek]

Hi Rita,

As long as the NI-4351 board is plugged in and powered, you should be able to read 1mA between the IEX1 pins. There is no switch for it. The NI435X Set Current Source function just sets the proper current excitation value for use in the calculations performed within the driver. This is its sole function. 

Regards,

Kent

Applications Engineer