If you have not already done so, you may want to read through the Boonton 260 Q Meter manual.
It is a wealth of information and provides a lot of insight on where errors creep into measurements.
The manual can be found at the following link:?
Boonton's approach was to use a 20 milliOhm precision resistor with an attached thermocouple that
drove a panel meter. By measuring the power dissipation of the resistor, they obtained a known
voltage drop across the resistor. The integral VTVM measured the voltage across the tuned circuit
and the display meter was scaled in Q based on the results of the ratio of the tuned circuit voltage
to the voltage across the precision resistor.
HP bought out Boonton and marketed the 260A for a few years before presenting the HP4342 series
of Q Meters. I have not confirmed but was told that HP abandoned use of the precision resistor in
the 4342A. I used the 4342A for years in the 80's through the early 2000's. It is a tough box and in
my opinion, if you can buy one with unmolested innards, it is well worth the cost of repair and calibration
in a metrology lab.
