Q: What causes the readings to drift slowly after the power meter is powered on?
A: Slow reading drift is usually caused by environmental thermal interference, as thermoelectric power meters are highly sensitive to temperature changes.
Cause 1: Fluctuations in Ambient Temperature
Changes in ambient temperature directly affect the cold junction reference temperature of the thermoelectric sensor. When the rate of temperature change exceeds 1°C/min, observable reading drift occurs. In high-precision measurement scenarios, a temperature fluctuation as small as 0.1°C can introduce detectable deviations.
Solution: Place the instrument in a relatively stable environment, away from temperature fluctuation sources such as doors, windows, air conditioning vents, and heating units.
Cause 2: Airflow Convection Altering Heat Dissipation
Naturally cooled power meters rely on surface convection for heat dissipation. Air movement caused by fans, air conditioning, or personnel walking can change the heat dissipation rate at the probe surface, disrupting the original thermal equilibrium. The smaller the power range, the lower the probe's heat capacity, and the more significantly it is affected by airflow.
Solution: Turn off surrounding fans during measurement and avoid direct airflow on the probe.
Cause 3: Thermal Radiation Interference from Nearby Heat Sources
Nearby high-temperature components (lasers, power supplies, hot plates, etc.) transfer additional heat to the probe through thermal radiation, essentially superimposing a "thermal background noise" on the laser signal.
Solution: Keep the power meter at a sufficient distance from heat-generating equipment, or install a thermal barrier in between.
