Thermometry - Calibration Services

Ordering Calibrations Services

The Thermometry Group maintains the International Temperature Scale (ITS-90) in Canada. It disseminates temperature standards through its calibration service and through support for the INMS Calibration Laboratory Assessment Service (CLAS). Current research is directed towards improvement of both the primary standards of the ITS-90 and instruments and techniques for practical temperature measurements.

 Services
 Facilities
 Fees

Contact: Doug Gee
Tel. (613) 993-2393

Services

A complete range of temperature calibrations is available for resistance thermometers, liquid-in-glass thermometers, thermistors, thermocouples, and optical pyrometers. Special arrangements can be made to calibrate other temperature-measuring devices. The laboratory normally calibrates only first-class thermometric instruments. It may refuse to undertake certain, or all, methods of calibration for inferior instruments. It can advise clients on the selection, use, and appropriate calibration of thermometers for any aspect of temperature measurement.

Facilities

The Group has a complete set of primary standards (calibration equipment and thermometers) which enables it to realize the ITS-90, in accordance with its definition, from 14 K to 2500 K. In addition, there are calibration facilities for all the types of thermometers commonly used in the above temperature range. Furnaces, cryostats, and measuring equipment are also available for studies of melting and freezing points of high-purity materials as temperature reference points, for annealing of electrical thermometers, and for examining the behaviour of temperature-measuring instruments.

Fees

Ordering Calibrations Services NEW procedures effective March 23, 2006.

 Liquid-in-Glass Thermometers and Digital Thermometers
 Standard Platinum Resistance Thermometers
 Capsule-type SPRTs
 Long-stem SPRTs and HTPRTs
 Thermocouples, Thermistors, and Resistance Thermometers
 Optical Pyrometers
 Strip Filament Lamps

Liquid-In-Glass Thermometers and Digital Thermometers

Liquid-in-glass thermometers suitable for calibration are generally of the total immersion, ASTM-designated type with Serial Numbers. These thermometers include an ice-point reference scale which should be routinely monitored. Calibrations are made by comparison with a standard platinum resistance thermometer in a constant temperature bath within the temperature range -80^oC to +500^oC. A calibration consists of an ice-point reading and typically calibrations at 3 to 5 temperatures within the range of the thermometer. The thermometer is read to approximately one-fifth of a scale division. Hand-held digital thermometers suitable for calibration generally have thermocouple, PRT or thermistor input sensors and a digital readout display calibrated together. Calibrations are made by comparison with a standard platinum resistance thermometer in a constant temperature bath within the temperature range -80°C to +500°C, or by comparison with a standard thermocouple in an electrically heated furnace between 300°C and 1100°C. A calibration consists of measurements at 3 or more temperatures within the range of the thermometer.

Standard Platinum Resistance Thermometers

The standard platinum resistance thermometer (SPRT) defines the ITS-90 within the range 13.8033 K to 1234.93 K, when calibrated at specific sets of defining fixed points, and used with specified reference and deviation functions for interpolation at intervening temperatures. The defining fixed points are listed in the following table.

The ITS-90 contains a number of overlapping subranges. The calibration of a particular SPRT involves selecting the range over which the thermometer will be used, or the maximum range over which the SPRT may be operated in accordance with the recommendations of the manufacturer. SPRTs may be broadly classified into two types: capsule thermometers and long-stem thermometers. Capsule thermometers are used primarily between 13.8 K and 273 K and, by the nature of their construction, generally become an integral part of the apparatus in which they are used to determine temperature. Long-stem SPRTs (25 at 0^°C) normally operate between 84 K and 660^°C. The high-temperature platinum resistance thermometer (HTPRT) (0.25 to 2.5 at 0^°C) may be operated to 961.78^°C.

Preliminary Preparation and Testing

Capsule-type SPRTs

(A33-03-02-02 to A33-03-02-05)

Calibrations of capsule-type SPRTs are available for the following temperature ranges:

Long-stem SPRTs and HTPRTs

(A33-03-02-06 to A33-03-02-21)

The following services are provided for long-stem SPRTs and HTPRTs. The temperature ranges are as shown for each calibration.

Platinum-rhodium Thermocouples

Standard platinum 10% rhodium/platinum thermocouples (type S) must be at least 90 cm long and made of wire not less than 0.35 mm in diameter. It is recommended that a standard thermocouple be at least 120 cm long and be shipped as bare unstrained wire. This is to facilitate the annealing of the thermocouple wire at high temperature (1300^°C) by electrical heating prior to assembly. Such a thermocouple will be returned assembled in a pure alumina sheath 46 cm long and 4 mm in diameter, with a pyrex-enclosed reference junction and with 150 cm selected copper leads. Platinum 13%rhodium/platinum thermocouples (type R) of the same construction will also be calibrated under A33-03-03-03.

Thermocouples, Thermistors, and Resistance Thermometers (Including laboratory grade digital thermometers)

This category includes both individual sensors (thermocouples, thermistors, industrial resistance temperature detectors) and various digital instruments which read directly in terms of temperature. Calibrations are performed by comparison against SPRTs or standard thermocouples which determine the calibration temperature. The comparison facilities include a variety of baths, furnaces, and cryostats. Each calibration involves A33-03-04-01 and one or more of A33-03-04-02 to A33-03-04-05.

Optical Pyrometers

Optical pyrometers are calibrated using previously-calibrated tungsten strip-filament lamps as transfer standards. The lamps are calibrated against a blackbody at the freezing point of silver using a primary photoelectric pyrometer to develop a calibration for the lamp in terms of spectral radiance temperature (near 660 nm) as a function of dc current. The use of spectral radiance temperature rather than true filament temperature is a result of the (unknown) emissivity of the tungsten filament. As a consequence, the lamp calibration is valid only near 660 nm. Vacuum-filled lamps calibrated in this way are suitable for operation to 1500^°C. Above this temperature, lamps filled with an inert gas must be employed to avoid excessive vapourization of the filament. The gas-filled lamps are calibrated by scaling procedures based on a vacuum lamp as the standard source, rather than a blackbody. The gas-filled lamps may be operated to 2200^°C. Only pyrometers with a field-of-view (or spot size) suitable for use with a strip-filament lamp and with an operating wavelength near 660 nm may be calibrated in this manner. Other pyrometers and radiation thermometers may be calibrated by special arrangement.

Strip Filament Lamps

(A33-03-06-01 to A33-03-06-02)

Tungsten strip-filament lamps (vacuum and gas-filled) may be calibrated for use as transfer standards for the calibration of optical pyrometers. The calibration is performed by comparing the lamps to be calibrated with lamps which have been previously calibrated against blackbody standards using a primary photoelectric pyrometer.