Characterisation of measurement uncertainties due to preamplifier gain variation

The measurement uncertainties associated with preamplifier gain variation due to temperature change are investigated. It is shown that when temperature decreases from the room temperature (25°C) to 0°C, the uncertainty of the preamplifier gain variation is found to be as large as 1.277 dB. Further investigation of mismatch uncertainty between the preamplifier and the system due to temperature change has been carried out. It is expected that mismatch uncertainty will be greatly affected if the preamplifier input and output voltage standing wave ratio varies at different operating temperatures.