myDAQ with LM35 Sensor

[yogece]

I am using LM35 temperature sensor with myDAQ for powering the sensor with a benchtop powersupply of 6v;since the output from the temperature sensor is in the range of few millivolts(10mV/deg Celsius)  I couldn't get the stable reading on labview(values are highly oscillating).when i power the LM35 using myDAQ 5V don't have any measurement error.can you provide a solution or is possible to acquire low voltage without noise

[Kristoff2]

Hey yogec

When you power the sensor from the benchtop supply are you also connecting the myDAQ AI Ground to the LM35 ground and the benchtop supply ground?  You should have no problem reading milivolts using myDAQ, its probably just a connection or grounding issue.

Let us know if that helps or if you have more questions.

Thanks!

-Sam K

LabVIEW Hacker

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[yogece]

hi Sam,
I have given connection's correctly. I don't think the problem is because of grounding and connection; when I connect a long wire with the input terminal it's picking up the 50 hz mains supply how can I avoid this problem.

Thanks
Yogeswaran

[Kristoff2]

This guide has tons of good info on wiring, signals and noise.  I think you're either going to need to add a low pass filter or use shielded cables.

Good luck!

-Sam K

LabVIEW Hacker

Join / Follow the LabVIEW Hacker Group on google+

[yogece]

Even today I faced a strange problem when a 9V battery connected with AI of myDAQ initially it shown 9V and later it got exponentially (used a Graph) reduced to 1V and when I tested the battery with Multimeter it shown the correct value. What might be the problem?

[yogece]

Thanks for the valuable link Sam.

I am taking care of labview student projects of our college and use myDAQ,NI-USB DAQ.Every day facing strange problems when using the hardware

[Kristoff2]

This is sort of a long shot, but I've seen it before so I'll mention it.  If you're using a cheap power supply its possible that attaching the power supply ground to the myDAQ ground creates a ground loop which is browning out the myDAQ.  I ran into this when I was using a cheap benchtop supply with a microcontroller dev kit attached to my laptop.  When my Laptop and the power supply were connected (through the dev board) and both plug in the dev board would brown out, and I fried some components (including my in circuit debugger).  If I unplugged the laptop and ran on batter power it was fine.  We eventually traced it back to the combination of a cheap bench top power supply and the wiring in the lab we were in.

If you can test with a laptop running on batter power I would be interested to see if that changes anything.  Have you used the myDAQ on another PC (outside your lab)?  Does this happen with multiple myDAQs?  If it's just one it's possible it is damaged (maybe from the ground loop issue) but the is a lot of protection circuitry inside the myDAQ to prevent this.

You could also check the fuse to see if its partially blow.  Another long shot but an easy thing to check.  Details in this doc.

-Sam K

LabVIEW Hacker

Join / Follow the LabVIEW Hacker Group on google+