Other Contact Sensors

This is the “Other” category.

There are lots of different temperature sensors that are offered commercially but in relatively small numbers because they are suited to only a very limited purpose use or the developer(s) have been unable to crack through the mass market for any number of reasons.

The most common one is price. These are usually very expensive devices and are for the most part built to orde, if available commercially at all (sometimes people have to build their own or someone else’s unpopular design device just to gain the special capabilities possesses).

If  what you seek is still not here, send a note. This is an interactive site and grows over time…faster with input from you!

If you know of some “Other” sensors, let us know so we can add them to the page.

Visit periodically to learn what’s new!

Thanks for visiting.

Acoustic and Ultrasonic

The concept of measuring temperature in a gas by measuring the speed of sound in that gas has been exploited by several groups.

Another variation on the same idea has been to send ultrasonic pulse down a rod of known expansion and propagation properties.

By placing slots in the rod at known and calculable distances from the excitation position, one could immerse the rod in a medium of high temperature and then measure that temperature by measuring the reflection times of the pulses from the notches.
A vendor of these devices is:

SEI in Nevada-USA
An innovator in acoustic pyrometers for measuring the temperature of hot gases in the combustion chambers of boilers.

Noise Thermometers
Johnson noise thermometers have been around for 30 years or more.

They are very complex and were difficult to fabricate with the electronics of 30, 20 even 10 years ago. That’s changing rapidly as better and better IC circuits become available and the processing capability of micro-computers continue to grow.

The best way to appreciate what can and has been done with these devices is to check the links.

Much R&D has been done on Noise Thermometry by the Instrumentation Group at The USA Department of Energy’s Oak Ridge National Laboratories and more recently the Thermometry Group at NIST in Gaithersburg MD, USA.

Suction Pyrometer
You’ve never heard of it, right? Many people are in the same fix as you.

The name sounds familiar but not exactly a household word. Yet these radiation-shielded thermocouple devices make a real difference in the measurement of high temperature gases. They are even made commercially by a few companies on a regular basis

A vendor of Suction Pyrometers was (for many years): Land Combustion Division of Land Instruments, International

But they have dropped the product line not long after being acquired by a major instrument company.

However, we recently (2009) learned that a French company, Pyro-Contrôle, makes them under the product designation: “Aspiration Thermocouple Assemblies”.

Venturi Pneumatic Pyrometer
That doesn’t ring a bell either.  But they existed and sometimes are the only device to measure gas temperatures at temperatures above the range of thermocouples (>1700°C). Big, bulky and cumbersome, they are nonetheless the only way to go when nothing else works.

A vendor of Venturi Pneumatic Pyrometers used to be: Land Combustion Division of Land Instruments, International

Optical
There must be a dozen, if not more, variations on techniques to measure the temperature of an optically active sensing element that has some property that varies in a known fashion with temperature. Polarization, transmission, expansion, band-gap edge shift are but a few such properties.

Aside from the ones covered here under fiber optic sensors, most are “home-brew” devices and there do not appear to be any on the commercial market…yet. If you know of one, let us know, please!

Needless to say, we’ve left room for expansion on this page, because it will be needed someday!


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