Sensitive quick digital thermometer

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Discussion Overview

The discussion revolves around identifying a suitable digital thermometer for detecting sudden temperature changes, specifically in the context of measuring temperature variations in clothing due to sweating. The focus is on the requirements for quick response time, flexibility of the sensor, and low power consumption.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks advice on a thermometer that can detect a temperature change of at least 2 degrees Celsius within 10 seconds, emphasizing the need for flexibility in the sensor material and length.
  • Another participant suggests thermocouples due to their quick response time but notes their localized detection capability, prompting a request for further clarification on the application.
  • A later reply mentions the challenge of finding a 'large area' thermometer and suggests that most traditional thermometers are point-like detectors, proposing the use of indicator dyes or paints as an alternative.
  • Another participant proposes using multiple thermocouples and discusses the potential issues related to data viewing and transmission, while also suggesting thermistors as a possible solution for averaging temperature readings.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of using traditional thermometers for the described application, with some suggesting alternatives like thermocouples and indicator dyes. The discussion remains unresolved regarding the best approach to meet the specified requirements.

Contextual Notes

Participants note limitations related to the localized nature of most thermometers and the challenges in data collection and transmission for the intended application.

Haawky
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Hi,
I am wondering if anyone can advice on which kind of digital thermometer would be most suitable for the following conditions:

1. It should quickly be able to detect a sudden increase in temperature. The actual temperature is not important, only the detection of a sudden change in temperature by at least 2 degrees celsius within 10 seconds.

2. The heat sensor of the thermometer should be of a flexible material (easily bends, e.g thin metal) and should be about 20 cm long and be able to detect the change of temperature anywhere along its length.

Thanks for any advice!
Best wishes,
H
 
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What is your application? Thermocouples can have a negligible thermal mass (quick response), but are very localized. Can you elaborate more on (2)?
 
Andy Resnick said:
What is your application? Thermocouples can have a negligible thermal mass (quick response), but are very localized. Can you elaborate more on (2)?

Hi Andy and thanks for your reply!
It is for a device that will measure sudden change of temperature in clothes due to e.g sweating. It is for a very special project and the device needs to be small and flexible so that it does not destract the wearer. It also has to be low power consuming since it can not have a huge battery and it should be used for a long time. But I guess most electric thermometers do not consume so much power?
It will be applied on different areas of about 20cm each for measuring and if a temperature increase occurs anywhere along that 20cm line, the device should register it.
I hope this makes sense. What kind of thermometer would you suggest for this project?
/H
 
I don't know of any 'large area' thermometer. Most thermometers (and I include thermocouples, thermistors, RTD elements) are (basically) point-like detectors. Short of stitching together an assembly of fine-gage thermocouples, there are indicator dyes/inks/paints that may be sensitive enough:

http://www.omega.com/toc_asp/sectionSC.asp?section=F&book=temperature

good luck!
 
I'd consider multiple thermocouples. The thermocouples themselves aren't the problem: the problem is how to view/record/transmit the data from a person to where you want to view/use it. Could you describe in some more detail how you physically hope to use the data? There are, for example, pager-sized data loggers that can take multiple inputs.

Also a possibility, thermistors: you can wire a bunch of them together for an average temperature reading.
 

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