The accuracy of power and energy meter calibration is dependent on many factors. Among others, these factors include:
1. Wavelength: Measuring heads need to be calibrated at a few wavelengths since absorption differs with change in wavelength.
2. Linearity: If power/energy input is increased by a factor of, say, 2, do we get twice the reading? The linearity error should be minimal, usually not more than ±1%.
3. Uniformity: If the meter head is calibrated with a small laser beam in the center of the absorber, how much will this change if the beam is not centered or is larger in size?
4. Pulse rate and pulse width dependence: This is only important in pyroelectric heads. How much does the reading vary depending on the pulse rate of the laser? There is usually some pulse rate dependence in pyroelectric heads but it is minimal for pulse rates less than 70% of the maximum pulse rate. Pulse width dependence should be minimal.
5. Display: Often the error of calibration of the display unit is so minimal compared to the calibration error of the measuring head. In those cases, this error can be ignored.
6. Damage done to the absorber surface: To test if damage to the absorbing surface is affecting the readings, the beam can be moved away from the damaged area to see if the absorption changes. It is considered significant damage if the reading is off by 1% or more.
These are the main factors taking into consideration, among a few others, when creating a viable calibration tool. If you’d like to learn what Ophir does to ensure calibration accuracy of measuring heads, you can read the article by Ephraim Greenfield, CTO of Ophir Optronics, Ophir Power/Energy Meter Calibration Procedure and Traceability/Error Analysis. You can also contact Ophir Optronics to make an appointment to have your meter calibrated.
You might also like to read: Factors that can impact the accuracy of the laser/power measurements
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