# monitoring oven temperature

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#### pc88

##### New Member
I'm interested in monitoring the temperature of my oven. 600 degrees Fahrenheit would be sufficient.

1. Use a thermocouple like shown here: Microcontroller-based Temperature ... - Google Book Search
Challenges: Need a cold junction compensator and an amplifier.
Cost: $15 for a Type-K thermocouple +$15 for an AD595 (sourced from sparkfun.com)

2. Use a Thermistor.
Challenges:
Need to find an insulator for the wires to the thermistor that can withstand the oven temperature.
Need to find a thermistor rated for 600 F
Cost: \$3 for the thermistor + ??? for the wire insulation.

Any suggestions or alternatives?

#### dknguyen

##### Well-Known Member
I would go with a thermocouple over thermistor. Partly due to preference, and partly due to both being non-linear, but thermocouples being standardized while thermistors aren't. Thermocouples are more durable and are inherently "in wire form" to act as a probe.

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#### stevez

##### Active Member
You might consider the following:

A. That temperatures may not be uniform in all areas of the oven as a result of losses thru the walls of the oven.

B. If the objects you are heating in the oven can "see" the heating elements they might get hotter than your means of measurement will indicate - unless of course you are measuring the temp of objects to be heated directly.

None of these may be of critical importance but I thought it worth mentioning.

#### Super_voip

##### New Member
600deg sounds extreme for an oven, at least at home.

#### pc88

##### New Member
600 F is a bit extreme, but it's not that far away from 450/500 F which is what you cook pizzas at.

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#### jbeng

##### Member
A thermister [usually] has it's leads soldered on to the element, which would likely melt at the temp you're wanting to measure, while thermocouples are usable for temps considerably higher ...

Jeff

#### dknguyen

##### Well-Known Member
A thermister [usually] has it's leads soldered on to the element, which would likely melt at the temp you're wanting to measure, while thermocouples are usable for temps considerably higher ...

Jeff

Good point. What were the temperature limits of thermistors? You might be able to rule them unfit for your temperature range altogether. That'd certainly make the decision a lot more concrete and easier.

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#### Boncuk

##### New Member
If there is an aircraft junk yard in your vicinity you might try to "shoot" a 'TGT-meter' (turbine gas temperatur). They are selfcontained, so no external circuitry is necessary and measure temperatures up to 1,500deg/C.

I used the TGT-meter of a T-33 for my funbuggy and fit it directly in the exhaust pipe close to the cylinder heads. At full power (with water-methanol injection) the "TGT" was 1,300deg/C.

The extra length of cable (no plugs!) can be wound to a spiral (don't cut. The device is unusable after cutting the cable).

Assuming you intend to use the sensor in an SMD soldering oven it is best to measure on a piece of PCB next to the one to be soldered to keep errors at a minimum.

Boncuk

##### Banned
Thermocouples are better if not the only practical method for measuring high temperatures, 600 degrees is I think past borderline practical for using a thermistor. Thermistors make good cold junctions because they're at completely sane temperatures usually and relatively stable in those ranges.
Mind you 600 degrees doesn't sound too much higher than 500 degrees which is pretty close to pizza cooking temperature until you also take into account that full spheroidal annealing of high carbon steel occurs at 'only' 700 degrees. Simply put the molecular structure of 'ordinary' materials changes dramatically at those temperature ranges. For human reference we would be a cloud of water vapor and a small pile of carbonized metallic elements at the same temperature.

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