Calibration of Pyrometers at The National Laboratory

Purpose

The national laboratories are responsible for maintaining the national reference standards for each measurement quantity and  spreading metrological competens and traceability to industry and society at large. The national reference standards are the highest level of traceability in Sweden. .

A calibration performed at a national laboratory fullfils all typical traceability and accreditation requirements that commonly exist in industry and society at large.

Method

We have a unique equipment for calibrating IR pyrometers in the range -20 ° C to 1600 ° C, with measurement uncertainties better than 0.5 ° C.

Measurements in Black Body Radiators

The calibrations are performed by measurements in black-body radiators of the type heat-pipe with water, cesium and respectively. sodium or in commercial black body radiators. The black body jets are designed as a conical bottom cylinder or as a sphere, giving emissivities very close to the ideal black body = 1. The pyrometer to be calibrated is directed towards the black body radiator and the pyrometer indication is noted. The temperature in black-body radiators of the heat-pipe type is determined by a resistance thermometer or thermocouple, while the temperature in other black bodies is obtained from one or more of RISE's pyrometer norms.

Heat Pipe

The heat pipe consists of a closed, double-walled tube filled with a substance that evaporates in the heat pipe's working area. The pipe whose one end is terminated with a cone (120 °) is placed in a horizontal tube furnace with temperature control. When the furnace has heated the heat pipe to the desired temperature, the temperature gradients are equalized by the heat transport of the steam. In the hot portions the filling is evaporated whereby heat is bonded and in the colder portions the steam is condensed into liquid which is transported back by capillary action in an inlaid 'wick'.

Calibration by comparison

Industrial IR pyrometers and two-color pyrometers are calibrated by comparison in our black body radiators with our pyrometer norms.

Band lights and Pyrometers

Band lights and visual optical pyrometers are calibrated in the range 700 ° C to 2600 ° C.

Deliveries

The calibration results are reported in a digital calibration certificate in Swedish or English which states that the calibration was performed at a national laboratory.