Measuring Brick Temp: Thermocouple/Pyrometer & Microammeter

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Discussion Overview

The discussion revolves around methods for measuring the temperature of bricks within the range of 20°C to 800°C. Participants explore the use of thermocouples, pyrometers, and microammeters, considering practical aspects of their implementation in a circuit.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about the suitability of using a thermocouple or pyrometer for measuring brick temperature and mentions the need for a microammeter due to the high resistance of the brick.
  • Another participant suggests using an optical pyrometer for surface temperature measurement and describes the process of boring into the brick to place the thermocouple junction at its center.
  • It is proposed that both a pyrometer and a thermocouple could be used together, with a note on the necessity of calibrating the pyrometer against the thermocouple.
  • A participant expresses uncertainty about the voltage and connection method for the thermocouple, questioning whether the wires might overheat.
  • Concerns are raised about the effectiveness of a pyrometer at lower temperatures, with a suggestion that an IR pyrometer would be more appropriate for temperatures below a certain threshold above 20°C.
  • A participant shares an anecdote about using an IR detector for identifying hot spots in electrical systems, emphasizing the speed of infrared pyrometers.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of pyrometers at lower temperatures, with some advocating for thermocouples as a more reliable option across the entire temperature range. The discussion remains unresolved regarding the best method for measuring temperatures at the lower end of the specified range.

Contextual Notes

Participants mention various types of pyrometers and thermocouples without consensus on their comparative effectiveness at different temperature ranges. There are also uncertainties regarding the proper setup and calibration of the measuring devices.

cdm391
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How would I measure the temperature of the brick when it is between 20oC amd 800oC. Would I use a thermocouple/pyrometer?
If so, how would I put this in the circuit? Obviously, the resistance of the brick is high, so i will need a microammeter in series.
 
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An optical pyrometer - that will measure the surface temperature.

If you use a thermocouple, it is customary to bore into the brick (masonary drill) - along one of the axes, and place the thermocouple junction in the center of the brick. The thermocouple leads are then connected to instrumentation outside the furnace.

Or you can use both the pyrometer and thermocouple.
 
Astronuc said:
Or you can use both the pyrometer and thermocouple.
Most likely, you will have to calibrate the pyrometer against a thermocouple.
 
I'm doing the same thing. What voltage are you using, and how have you connected the wires to the brick? I was thinking metal plates on either face of the brick, but I dunno. I'm using a thermocouple with probe and measuring device, but I'm not sure where to put it on the brick yet. And another thing, will the wires get too hot and melt?
 
Oo, Chipy Chick is only up the road! Hello and welcome!
 
While the pyrometer would do great at 800C, it would not work for the low end of your range. I am not sure what the low end would be, but certainly well above 20C. Even a type K thermocouple, mounted per Astronuc, would give you good readings across the entire range.
 
For the low temperatures, an optical pyrometer would not work. Instead one needs an IR pyrometer.

I once worked as a maintenance person. One of my projects invovled working with an electrical engineer who roamed the local power grid to find 'hot spots' in the electrical system. He was using a liquid nitrogen cooled IR detector, and the brightness of the spot was a function of the local temperature. And he did find some poor connections.

Infrared pyrometers are ultra-fast - http://www.engineeringtalk.com/news/ipa/ipa104.html

http://www.wintron.com/Infrared/infrared.htm
 

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