@Peter
thanks. Yes, exactly, the meters themselves are really cheap. I currently don't have access to some blown 8481A or similar sensors, so I cannibalized a sensor cable :-( because the connectors seem to be HP specific ones and are not available e.g. at Mouser or so.
But yes, as soon as I have a working circuit, I will it design such that it fits into the normal housing for those power sensors. I also thought of milling my own housing which would be similar to the original HP housing anyways.
The cool stuff is that Agilent and Keysight still use the same interface (at least for some power meters) as far as I know, so the sensor should work with any of those!
@Ed
?thanks also. Yes, I tried to study on the interface between the 436 and the power sensor. The resistor you are talking about is called the mount resistor in the 8481A manual. Here is the general schematic of this sensor:
The service manual tells which resistor value is used for the different ranges. I think it will be possible on the homemade sensor to add a little switch to change the mount resistor value and therefore the range the meter uses - such, the same sensor could be used for different power ranges. The 436A power ranges are very limited, as far as I remember.
However, what I don't understand in the interface between the meter and the sensor is how the autozero circuit works, and I am also a bit unsure about the working principle of the amplifier formed by Q1 in the sensor (see schematic) and the OpAmp in the meter. Do you know more details about how it works?
Best
Tobias HB9FSX
