The tests conducted in part 1 and part 2 was run on my personal 53230A[1] ("53230A-1135"). It is not impossible that this counter has some malfunction or defect that cause the bias. I have since had the chance to borrow another 53230A[2] ("53230A-2985") from a calibration laboratory, and rerun all the tests.
I have also been in contact with an individual who has a 53230A and is intimately familiar with the workings of the instrument - he observed the same bias. I do not have his raw measurement data.
All tests were run with the counters referenced to a 10 MHz signal derived from the hydrogen maser as described in part 1. Input impedance was set to 50 ohms, SAMPle:COUNt
was set to 25 and the data collected with 1000 individual calls to READ
. The tests were run on both counters in parallel.
The temperature on the room was kept at better than 22°C +/- .5°C for the duration of the tests.
The data presented below. Red is 53230A-2985, blue is 53230A-1135.
Both counters show the bias in varying degrees. Both counters seem to show bias of roughly the same order of magnitude, 53230A-1135 performing perhaps sightly worse.
The 33510B was clocked from the same 10 MHz distribution amplifier, set to produce a 4Vpp sinewave output on both channels. Channel 1 was connected to Channel 1 on 53230A-1135, channel 2 was connected to channed 1 on 53230A-2985.
The 33510B was configured and connected as in the previous test, gate times set as multiples of 3. 3 second gate time was not tested.
Unprocessed data used to create these plots available here
I also tested input 2 on the counters, with the same results. Data is included in the datafile above.
The bias is not a results of a single defective 53230A. The magnitude of the bias varies between counters, perhaps a result of manufacturing process differences.
Agilent Technologies,53230A,MY50001135,02.07-1626.4446-1.19-4.15-127-155-35
Agilent Technologies,53230A,MY50002985,02.05-1519.666-1.19-4.15-127-155-35