LM 35 sensor

[Ivor Ahern]

Hi, I am using a lm 35 temperature sensor which is powered by a pc through matlab via a data acquisition card. I am measuring the temperature of a bulb. The problem I am having is its picking up a lot of noise from ambient temperature until around 47/48 degrees and then it stabilizes out.

 

[Les Jones]

You need to provide more information. Post the schematic of the data acquisition card and how the LM35 is powered and connected to the card.

Les.

 

[alec_t]

If the instability is due to thermal effects then thermal screening/insulation will help.

 

[Ivor Ahern]

Hi guys, thanks for the comments. The card I am using is a National Instruments TBX 68 data acquisition card. The sensor is powered from pin8 (5volts) and the return is back on pin 68 and the ground is pin 67.

Cheers

 

[atferrari]

I like the way you ignored the request for a schematic.

 

[Ivor Ahern]

Is there any other calibrated sensors on the market similar to the lm 35?

 

[KeepItSimpleStupid]

Bulb doesn't mean much. Vibration affects high voltage bulbs (e.g. 120 vac). The filament bounces.

 

[gophert]

Is there any other calibrated sensors on the market similar to the lm 35?

Yes, but you can still make design and assembly errors with those, too. The LM35 is the easiest one so, if you are having troubles, I would recommend you share your secret schematic so we can help you walk before you try to run.

 

[fezder]

Yeah, lm35 is pretty much plug'n play so schematic would help a lot!

 

[AnalogKid]

Why do you want to measure the temperature of a tulip?

 

[atferrari]

Currently using an LM335. If you press me, I hardly could say the 35 from the 335. In any case I will refuse to show my schematic...!

 

[canadaelk]

The LM35 is by no means calibrated. The military spec version has a lower tolerance though.
Who said it was a tulip. The OP said bulb. It could have been a Snowdrop. I like them. E

 

[AnalogKid]

Still waiting on a schematic from the OP. I think his bulb is dim.

 

[gophert]

Still waiting on a schematic from the OP. I think his bulb is dim.

I suspect his issues had something to do with an op amp not being able to sense all the way to ground - it only started working at 40C (400mV).

 

[ChrisP58]

Hi, I am using a lm 35 temperature sensor which is powered by a pc through matlab via a data acquisition card. I am measuring the temperature of a bulb. The problem I am having is its picking up a lot of noise from ambient temperature until around 47/48 degrees and then it stabilizes out.

If the sensor is getting noise from ambient temperature sources, then the problem is more likely how the sensor is thermally coupled to the bulb, rather than some electrical issue.