[Amps] Measuring power

[Steve Thompson]

In case anyone might be interested, I looked out some data on a couple of the 
power meter systems I use here.

The 'better', more modern, one uses HP8481A sensor which appears to be a 
bolometer - the sensor is a thermocouple attached to a resistor.

The older one uses HP478A sensors, which uses a technique similar to one 
described by G8WRB. Four thermistors are mounted close together. The rf to be 
measured heats up one pair and a feedback system ends up applying a similar 
amount of dc power to the second to maintain balance. The dc power is 
measured and used to indicate the rf power.

Steve