Reference Blackbody Source.
A precision calibration reference blackbody is used as a calibrated source of IR energy. This is the commercial large area blackbody source M315X (Figure 1 ), manufactured by the company MIKRON. The blackbody uses a precision platinum RTD and a digital PID controller. The calibration process has been carried out under laboratory environmental conditions, using a radiometric method, which ensures the temperature homogeneity of the emitting surface. The calibration certificate of the instrument is provided by the manufacturer.
The most important characteristics of the blackbody are the following:
- The surface spectral emissivity measurement has been performed by NIST (National Institute of Standards and Technology), and is provided by the manufacturer over the whole GTS characterized wavelength range.
- The controller permits to reach temperatures from 293 ºK to 673 ºK, and the blackbody short term stability error is ±0.1ºK for an 8 hour period.
- The emitting surface has a diameter of 8’’.
- A thermometric method is used to measure the real temperature of the blackbody emitting surface. The method uses an ultra precision platinum RTD that closely monitors the temperature of the emitting surface. A deep hole with 3.5mm diameter is provided for customer insertion of the calibrated RTD. This RTD has been previously calibrated at INTA facilities in the Metrological and Calibration Department, in an isothermal chamber following the recommendations of EIT-90.
- Knowledge of emitter emissivity characteristics, provided by the manufacturer, is needed for correct radiated energy computation. Using this method an accuracy over 20mK can be reached in the temperature of the surface.