Found Cheap Electronic Thermometer

[n3umw]

I have not tried one of these but I guess this meter would make a good thermal sensor. I ordered one figuring it is worth a shot at only $4. The probe looks to be metal so it should give fast updates/changes.

$4 LCD TEMPERATURE METER & PROBE
http://www.mpja.com/email/06-23-09a.asp?r=%%ref%%&p=16370+me

The same place has some other good deals on useful stuff like soldering irons, gel-cells, and 12v power supplies.

http://www.mpja.com/emailspecial.asp

[Andy W]

No, a thermometer will not sense thermals.
..a

[rdwoebke]

No, a thermometer will not sense thermals.
..a

This is not entirely true. I have a friend that has a thermal chart recorder and one of the main thermal detection things it uses is a thermistor temperature probe.

Simply looking at the temperature, I agree. But you can sense thermals with a very accurate charting tool.

[JRinAZ&MN]

I have one of the temperature modules you have in mind. It works, but the temperature is not accurate (not linear) and has a rather large metal probe. The mass of the metal would make it a poor choice for thermal detection.
JR

[Batmanwpg]

They are actually very good thermal detectors if you know how to use them. I used one for many years while flying free flight models and was very successful with it. Some are better than others. Try and find one that has a ceramic bead covering the sensor. They react faster. You can also peel away any plastic covering (insulation) around the sensor to help it act faster. The one thing you should also have is a shade cover for it that still allows good air to flow over it but keeps it out of direct sun light as this will give false readings. Put it on a pole so that it's up at least 6' off the ground. The higher the better.
If you plan on using for competition make sure the rules allow its use.

[n3umw]

I got the thermometer today and I'm sorry to say it only updates every three seconds. This is probably not fast enough to work well at detecting thermals.

I am looking into modifying it to update faster but as the circuitry is only a potted die-pack, a resistor and several capacitors, this does not seem likely.

The sensor is potted in a metal shield. If it updated faster, I would also like to replace the sensor with a bare thermistor. While the metal is a good heat sink, it (and the potting material) has enough mass to slow changes in readings. I went to Radio Shack and they no longer carry thermistors (even online).

For more information on using a thermometer, see Detecting Thermals at
http://www.apogeerockets.com/Education/detecting_thermals.asp