How To Eliminate Common Power Meter Mistakes

Modern wattmeters and power meters are simple to use and can provide digital measurement data to several decimal places in dBm or watts. Despite this accuracy, consistent power measurement remains elusive: different users regularly take measurements using similar tools and methodologies, only to come up with different numbers.
The most common reason for such disparity is user error, and correcting for the mistakes described here will dramatically improve measurement accuracy. Most of these issues are rooted in the fact that, when carrying out the most common power meter application — measuring a signal’s power level — users tend to forget that the power meter is not measuring exactly what they seek. Rather than the signal’s power level, specifically, the power meter measures total power over the sensor’s entire bandwidth.

When operating a power sensor with a correction table by frequency, the user must enter the percent correction, as shown on the sensor, correlating to the frequency being measured. When operating a power sensor with e-cal data, the user still must enter a frequency before the meter can apply a correction. Additionally, if the RF power level to be measured is not connected directly to the power meter head — whether the RF path is just an attenuator or an entire test bench setup — the user must account for the “slope” of the RF path to correct the measurement. Power meter users also must remember to calibrate based on any cables they use with the system and to remain mindful of signal-to-noise ratio.