Calibration – Why Isn’t It at My Wavelength?

December 19, 2018

Raphael Cohen

O.K, so you purchased an Ophir sensor to measure your laser, 808 nm for example.
Ophir states that the sensor range covers 808nm but when you opened your calibration certificate it says that it was calibrated ‘only’ at 1064 nm and 532 nm.

What’s going on?

Well, you’ve unexpectedly entered the world of calibration and uncertainty! There is a lot to say about Ophir’s calibration process and how it ensures such low uncertainty of measurement across the wavelength range of a given sensor. However, this isn’t the forum for getting into too much detail…

So here is the bottom line

Every sensor, whether it is thermal, pyroelectric or photodiode, has its own wavelength dependent response. Ophir characterizes these response curves with top of the line equipment using NIST traceable wavelength standards.

Once the response curve is known it is just a matter of calibrating the sensor at a wavelength along the curve and if it is in tolerance then the entire curve will also be good. Ophir goes one up on this and tests at a number of discrete wavelength points in order to ensure the best fit possible for the sensor wavelength response curve.

As a result, when you see that the calibration certificate gives only a few wavelengths out of the entire wavelength range you can rest assured that the response across the wavelength range is accurate. Since the response curve of the sensor is stored in the sensor head, all you have to do is input your wavelength into the display and it will automatically apply the wavelength response of your sensor to the measurement.

Special needs

Occasionally, a customer will want calibration measurements at discrete wavelengths other than the standard ones Ophir uses. In such a case it is possible to request special calibration.

For a more in depth explanation of the calibration process in Ophir, you can read additional information available in our knowledge database: https://www.ophiropt.com/laser–measurement/knowledge-center/article/1110