Tempurature Sensor

[chris31]

I am working on a project and I want to use a tempurature sensor to measure the tempurature of a liquid. Does anyone have any recomendations? It can be analog or digital.

[Andy Baker]

I am working on a project and I want to use a tempurature sensor to measure the tempurature of a liquid. Does anyone have any recomendations? It can be analog or digital.

I'm working on a project that involves the temperature detection of an engine control module for a major automobile manufacturer. Omega (http://www.omega.com/ppt/pptsc.asp?ref=OS101&Nav=temj11) has one that we are using, is inexpensive, and fits our needs.

Good luck,
Andy Baker

[chris31]

I'm working on a project that involves the temperature detection of an engine control module for a major automobile manufacturer. Omega (http://www.omega.com/ppt/pptsc.asp?ref=OS101&Nav=temj11) has one that we are using, is inexpensive, and fits our needs.

Good luck,
Andy Baker

I like the idea of that but its more heavy duty than what I need. Something cheap, accurate, and will work in the range of 0-50C, and easy to work with.

[seanwitte]

A thermistor is a component whose resistance varies with it's temperature. If you're using a microcontroller you can measure the temperature using an analog input. To connect the thermistor to the controller you connect one end to +5V and the other end to a 220 ohm resistor. The second lead of the resistor goes to ground. The analog input gets connected to the node between the resistor and the thermistor. The circuit is called a voltage divider. There is a large selection of parts at digikey.com. Radio shack might sell them as well. Excuse the ascii diagram, but you get the idea.
[code]
+5V
o
|
[ ] thermistor
|
o-----o to analog input
|
<
> 220 ohm resistor
<
|
o
Ground

[jgannon]

I'm not totally sure what your application is, but if all you want to do is visually monitor the temperature, you might see if your school has any CBLs lying around that you can use. The CBL is a device that plugs into most any TI graphing calculator, and comes standard with sensors for light, voltage, and temperature. The nice thing about this is that it won't cost you anything, and the application for 83+/84+ is graphically very nice. In addition, it is capable of doing data logging over time. Also, I'm almost certain that the temperature probe is waterproof.

Alternatively, you might consider picking up one of these (http://www.national.com/pf/LM/LM19.html). Jameco carries them for $0.34 a piece. This has an analog output that you can feed into a robot controller, or just monitor with a voltmeter. Since it is just a TO-92 case (like a small transistor), you will need to find some way to electrically insulate it, to protect it from the liquid.

I suspect that you'll find either of these solutions to be much more cost-effective and easier to use than the product in Andy's link.

[chris31]

Ill probably be interfacing it with a 2005 RC just for testing purposes before I have the rest done. Thanks for all of your input.

[Qbranch]

Just use a J, T, K, or S type thermocouple and a level converter IC.

The level converter can be found here. (http://www.national.com/ds/LM/LM135.pdf) I suggest the LM135 in the TO-46 Package. This will allow you to read in temperatures of -50C to 150C off of one of your analog inputs.

The temperature is read off in kelvins, with zero kelvin being zero volts. Calibration routine found here. (http://www.national.com/ds/LM/LM135.pdf#page=5)

I used a thermocouple/level converter for a science project back in 7th grade, these things work great and are very rugged. Simple circuitry too.

If you need help just let me know.

-Q

[yongkimleng]

For non critical applications with decent margins of error, the LM19 is pretty sufficient and pre-calibrated. Your only problem may be insulating it unless you can find the metal-can package of it so you can dip its "head" into the fluid, or drill a hole at the side of the fluid container to place it, ensuring that no fluid touches the electrical pins. Hopefully your fluid isn't charged too.. dunno if the metal case is grounded or not.

[Tatsu]

Just use a J, T, K, or S type thermocouple and a level converter IC.

The level converter can be found here. (http://www.national.com/ds/LM/LM135.pdf) I suggest the LM135 in the TO-46 Package. This will allow you to read in temperatures of -50C to 150C off of one of your analog inputs.

The temperature is read off in kelvins, with zero kelvin being zero volts. Calibration routine found here. (http://www.national.com/ds/LM/LM135.pdf#page=5)

I used a thermocouple/level converter for a science project back in 7th grade, these things work great and are very rugged. Simple circuitry too.

If you need help just let me know.

-Q

QFT

Thermocouples are accurate, easy to get and reliable.. for most of your stuff a thermocouple with an inamp works reall well.