Temperature Sensor DIY for calculators

[Csaba Tizedes]

Hello,

Have anybody experience with homemade temperature sensors measuring inside the electric owen how the temperature is changes around the setpoint?

I want to make this measurement up to 250-300 degC and if possible using thermistor connected to a calculator as a data collector unit?!

It is possible to collect and save data on a pocket calculator (time and temperature)? The electronics is how complicated if I want to use similar technology like Vernier on TI 83/84Plus?

Thank you for the answers!
Csaba

[Vtile]

Here is one example of using LM35 temperature sensor and I assume the AD and serial of the PIC to communicate with HP50g.

http://www.hpcalc.org/details/7306

You need basicly a four parts. A sensor, an amplifier, Analog to Digital converter, Serial link and calculator software.

I would personally use Pt100 or Pt1000 over NTC or PTC thermistors as they (PTs) are easier to handle with many magnitudes higher linearity. If LM35 style single chip devices can't handle the measurement environment (heat). The termocoubles introduces also complexity to the electronics as they need so called cold end compensation in another word they are measuring the temperature (in micro- and millivolts) differential between the cold and hot end of the thermocouble wire another thing with them is that they are far from linear.

As Platinum temperature resistors (pt100&pt1000) are almost linear by nature you might be good without even a linearisation in some cases. Pt100 is also defacto standard in industrial temperature measurement and been long enough that internet is floating with the amplifiers etc. analog circuit schematics to use. IIRC Burr-Brown (part of TI now) do have off the self pt100 bridge amplifier / transmitter chip. Pt1000 is easier as the ohms per Kelvin is bigger so you do not need as much accuracy (for amplifier) to your Wheatstone bridge or Kelvin sensing circuitry.

[cruff]

(11-26-2016 08:59 PM)Csaba Tizedes Wrote:  Have anybody experience with homemade temperature sensors measuring inside the electric owen how the temperature is changes around the setpoint?

I have experience doing this in a chemistry lab using K type thermocouples and an HP-IB connected DVM. The oven was manually constructed using fire bricks and was used to heat coal samples in glass vessels with bottled air feed in, with the output gas sent to a gas chromatograph. The data collection, reduction was done using a 9825 computer and the results plotted on a 9872 flatbed plotter.

(11-26-2016 08:59 PM)Csaba Tizedes Wrote:  It is possible to collect and save data on a pocket calculator (time and temperature)? The electronics is how complicated if I want to use similar technology like Vernier on TI 83/84Plus?

Yes, that is workable, you won't require much computing horsepower to do that. For a themistor, you will require a way to measure its resistance and the appropriate formula to convert to temperature. If I were to do it, I would use either my 41CL or 71B with a 3486A HP-IL multimeter and some sort of HP-IL storage.

[Dave Frederickson]

An HP-41, 3421A Data Acquisition Unit, and a Type T thermocouple.