lm35 fluctuating output labview

[manikyavalli]

Hi I am using lm35d for temperature measurement using labview. When Iam measuring voltage using elvis digital voltmeter, Iam getting correct temperature around 0.33v(33 degrees). But when I measure using DAQ assistant, it is fluctuating alot and also showing negative values around -0.12v. what could be wrong?

[GerdW]

Hi mani,

what could be wrong?

The settings of your DAQAssistent could be wrong. Or the cabling of your sensor could be wrong.

[manikyavalli]

My DAQ is PCI-6251. The DAQ settings I used are:

Aquire signals --> analog input -->voltage-->max: 6  min:-1, RSE, N samples

Connections on NI ELVIS are:

sensor Vout -> Ai0+

sensor GND pin -> elvis GND

sensor +Vs -> elvis GND

elvis AIGND -> elvis GND

please let me know any changes required.

regards

valli

[Dennis_Knutson]

What are the connections on the 6251? I suspect that is where the problem is.

[manikyavalli]

Actually I don't know much about connections between 6251 and elvis ( I thought it is just using 68pin connector). That is lab setup. I didn't looked that side. Could you please tell me how could be the connections and what could be fault? Is my connections between sensor and elvis is correct?  and corresponding daq settings also correct?

Regards

valli

[Dennis_Knutson]

You don't know which pin numbers you used625? For rse, you would need ai0 and gnd. Please look up the pin numbers in your manual.

There would not need to be connections between the Elvis and the 6251. There would needed to be connections from the sensor to the 6251'

[manikyavalli]

Actually I am measuring temperature using NI ELVIS prototyping board on benchtop workstation. I am connecting +vs pin from sensor to AI0+ point on prototyping board.  I am not connecting anything directly from sensor to 6251.

[Dennis_Knutson]

You first said the DAQ was a 6251. Now you say it's not being used at all?