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Originally Posted by JeepGuy
Looks good Yuri. Now for the dumb question of the day. If I get something like that put together, what do I need to get a read out from it? I guess I mean...could I simply rig up a plug to fit any digital thermometer unit and get accurate results?
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I was waiting for this question. You can't necessarily just connect any old sensor to any old digital thermometer - you have to know what kind of sensor was used in the first place (and there are lots of kinds). However, I do have a two answers for you, one simple, and one rather complex.
First, the simple answer:
If you have a digital thermometer that doesn't have a submersible probe, you can just encase the probe in some epoxy and stainless tube. That's what I was getting at with the "anyone can do this project" comment.
Now, the complex answer:
If you want to make a new probe for an old thermometer, some reverse engineering is in order. You can probably determine if a thermistor is the sensor of choice, because there will probably only be two wires on the probe output. Connect a multimeter and read the resistance value across those wires at several temperatures. That should give you an idea of the type of thermistor inside it. Here's a page from the
Jameco catalog that may help (as you can see, thermistors are cheap!).
If you've got three or more wires coming from the probe, it's probably a digital sensor like the LM34 that I used. Trying to reverse engineer one of those will likely fry it if you connect it backwards or apply too much voltage. In general, they operate at about 5VDC, red=positive, black=negative, green=ground, and other wire colors are likely to be sensor output. The sensor output will be something less than the input voltage. Jameco sells LM34 sensors for less than $5.00 a piece. I use the probe I made to feed my computer digital temperature information via an Arduino microcontroller (in short, I made my computer into a big digital thermometer).
Does that help?
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