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8.1.1.2 Method of Calibration
The absorption of the various Ophir thermal absorbers
can vary from disc to disc. Therefore, all Ophir
absorbers are individually calibrated against NIST
traceable standards.
Ophir power/energy meters with the broadband or P
type absorbers are individually calibrated by laser at
several wavelengths against a NIST calibrated
standard meter. The meter can be switched to give
the exact calibration at the various wavelengths
(Argon, YAG, and, where applicable, CO2); or, for some
models, an average value is given.
The EX type detector is calibrated by measuring the
ratio of absorption in the UV to that at 515nm. The total
absorption is measured in both cases using an
integrating sphere. The detector is then calibrated
with an argon laser and given a correction factor from
this ratio.
8.1.2 Linearity and Accuracy of Ophir Thermal Heads
8.1.2.1 Linearity
The linearity of most Ophir thermal detectors is
specified to be 1% over the specified power range of
each particular instrument. The linearity is tested by
electrical substitution heating. Models of up to 30
watts maximum rating are subjected to electrical input
up to their maximum rating, models of up to 300W
maximum rating are heated up to 100 watts, and
models of 1000W rating and above are heated up to
200 watts. On CAL models, the built in CAL resistor is
used.
On non CAL models, a CAL resistor is temporarily
affixed to the sensor. For those models for which the
linearity is not tested over their entire range, randomly
chosen sample models are tested periodically over
their entire range.
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