Temperature measurement with NI-USB 6009

[hkhiroya]

Hi,

I have the LM35D temperature sensor and am using the NI USB 6009 to read the values. I have setup the DAQ Assistant to a Analog Voltage input. The sensor gives a linear output to voltage +10mV / deg C with a range of 0 to 100 deg.

I have powered the sensor with 5V that the USB-6009 module gives and connected the signal wire of the module to one of the analogue input channels. The problem I have is when I measure the signal cable using a multimeter (still powered from the 6009 module) it give a reading around 240mV which is correct as that is around room temperature. If I hold the sensor I can see the temperature (voltage) going up.

As soon as I as connect it (the signal wire) to the analog input channel of the module and read values from the sensor it shows around 340mV and holding the sensor seems to have no effect on the reading. Even when measuring using a multimeter (probing the AI pin) it still shows 340mV.

Why is this happening? I cannot figure out where is this error coming from?

Any help will be appreciated.

Kind Regards,

Harshil.

[rsw]

Hi Harshil,

Sounds like a potential ground loop to me, are you reading the data in on the AI channel as differential? If you take a look here to check your wiring for the device, also are you reading this in using MAX test panels to ensure it's not software related?

Let me know how it goes,

Kind Regards,