Looking for IO card for thermistors


Thread Starter

Andrew Chiang

Hi all:

We are using 10K and 30K ohm thermistor. Are there any IO cards in the market that can use 30K ohm and 10K ohm thermistor?

Andrew ST Chiang
Mr. Andrew Chiang:

Opto 22 manufactures a SNAP-AIR40K-4 IO Card that allows you to interface with 0-10K up to 40K Ohm thermistors.

It can be used with any of Opto 22's BrainBoards that can give you a serial (RS-485), twisted pair-Arcnet or even an Ethernet interface to your I/O.

For more information on the module view Page 9 of the PDF datasheet at: http://www.opto22.com/Datasheets/1065_SNAP_Analog_Input_Mods.pdf

For more information on the interface brains you can choose any of the Brainboards listed at: http://www.opto22.com/_asp/globalsearch.asp?mode=simple&SearchString=b3000

Feel free to email me if you have any questions [email protected].

Rene Gamero

Curt Wuollet

Check with Omega, if anyone would have it they would. Actually any analog card can handle this single ended or bridged with a linearization equation or lookup table in software. If you don't
need lab accuracy, you can hook them to the joystick port on a PC for a no hardware solution. I wrote a 4 channel stripchart recorder for HVAC that worked this way long, long, ago in Turbo
Pascal. Worked a lot better than it had any reason to.


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OK you can design your own I/O card one of the old issues of Elector Electronics showed design of prom programmer board in which the designer made a separate add on card You develop a circuit to which your thermistor fits to use software like ORCAD and design an add on card

Curt Wuollet

Actually, you can simply do this with a terminal board a resistor and a stable source of power. For example with a 10 k thermistor you could use a 10 k resistor in series from power to ground and simply measure the voltage across the thermistor. (That's from the resistor/thermistor
connection to ground) Any garden variety ADC board can do that. Ohms law gives you the thermistor resistance and several sources give
various equations to calculate temperature. The one I have used is a set of three simultanious equations with a two point calibration. If you use standardized thermistors, the calibration is simply entering two values from the manufacturers table. You can code the equation or use it to produce a lookup table. I'd hate to see someone pay through the nose for a signal conditioning board when it is trivial to use thermistors with anything that can measure voltage and do a lookup. This is often what the SC board does anyway. You can also use a bridge if you want to use a differential input. It works the same way, solve for resistance and calculate or lookup
the temp.


Is it not too much bother to build your own electronics - with amplifiers, ADC , and UART - with a 555 timer .
I did it to convert an RS 232 printer to output of IEE 488 - whilst other parts made in ADC - no real difficulty to it - IF YOUR really that stuck then you will build your own. Learn a lot as well.
Bye for now - likkle david


Andreas Schweizer

I'm very interested in the Pascal Program by Curt Wuollet. I wrote a simple Basic Program to show the values of 4 thermistors.