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Measuring Heat with the Pyro Optical Pyrometer

by Sebastian Assenza

Many extraordinary scientific instruments found their way into the UTSIC collection after being deemed obsolete by one or more of the university’s professors or department administrators. New instruments inevitably supersede older ones which, considering the chronic lack of storage space in modern science departments, are either discarded or donated to museums or private collections. A fascinating exception to this rule is UTSIC’s Pyro Optical Pyrometer, a handheld device used to measure the temperature of an object by comparing reradiated light with a previously calibrated internal lamp. What makes this particular instrument so special is that similar pyrometers are still being produced and sold by The Pyrometer Instrument Company in New York. A quick comparison reveals that UTSIC’s pyrometer, made in 1940, differs from those sold online today in little but age and experience.

The Pyro Optical Pyrometer is an extremely rugged and easy to use device that serves a number of purposes. Advertised as an industrial apparatus used to remotely measure the temperature of molten metals or ceramics, the Pyrometer also comes equipped with a sturdy leather case. Along with its light weight, robust construction, and simple operating procedures, the Pyrometer is ideal for work in the field, as well as in the lab or the lecture hall.

Using the Pyrometer is a fairly simple process. The operator stands a safe distance from an extremely hot object (usually about twelve feet) and peers at it through the eyepiece. Inside the Pyrometer is a red lamp that surrounds the user’s view. In order to get a temperature reading, the lamp’s intensity is manipulated, much like the manual focus on a camera, until the colour of the lamp’s light matches that of the desired object. From there, a simple check of the previously calibrated temperature gauge should give you an accurate reading to within 1% of the target’s temperature. The entire process is both simple and reliable.

Our Pyrometer was finally donated to UTSIC in 1996, more than five decades after its manufacture. Despite its age, it remains in surprisingly good condition. The temperature and focus calibrations can still be easily manipulated while looking through the eyepiece and the corresponding gauges can be easily read. Indeed, the only thing preventing the Pyrometer’s use is a missing battery. Such durability and reliability speak to the instrument’s usefulness as a tool for the field, as well as its continued commercial success.

The most striking feature of UTSIC’s particular Pyrometer is the presence of handwritten numbers next to printed degree lines on the temperature gauge. Since the lamp within the pyrometer must be calibrated with a radiating body of a known temperature, the handwritten numbers may be evidence of the actual calibration process undergone by this specific device. Unique features like this reveal the painstaking efforts that go into creating instruments that must simultaneously be both rugged and precise.

The Pyro Optical Pyrometer is an intriguing example of a multipurpose device that can easily stand up to the rigors of use as both a scientific instrument and a teaching tool.