Two RF power meters are on hand, one is HP438A with a HP8481D sensor, the second is HP5347A with a HP8484A sensor. Using various attenuators I am not able to make any sense of the readings I am getting from the built-in 50mhz test source in each instrument. The readings are low by approximately 30%. (unit is reading .7 microwatt when it should be reading 1 microwatt.) Making readings with the two instruments and test signal outputs gives the same results on both instruments. They both read approximately the same power level and it is about 30% low. So either I have two different instruments with the same problem or I have a concept problem.
Using a scope on the reference output (with a 50 ohm termination) I read 1 volt peak to peak. The power chart shows the voltage should be .622 volts peak to peak for 1 milliwatt, in 50 ohms. If anything, the reading on the sensor should be high, I would think! Both instruments have the same 1 volt peak to peak output on the reference, and read the same value from the sensor, so either both failed the same or something else is wrong. The scope is a HP54622D (very nice scope) and tested on a voltage standard is within one small division. Anyone have experience with these types of power meters?
Using a scope on the reference output (with a 50 ohm termination) I read 1 volt peak to peak. The power chart shows the voltage should be .622 volts peak to peak for 1 milliwatt, in 50 ohms. If anything, the reading on the sensor should be high, I would think! Both instruments have the same 1 volt peak to peak output on the reference, and read the same value from the sensor, so either both failed the same or something else is wrong. The scope is a HP54622D (very nice scope) and tested on a voltage standard is within one small division. Anyone have experience with these types of power meters?