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Fast (?) frequency measurements via the 34972A

Question asked by bwalch on Jan 22, 2016
To make a very long story short, I've tried multitude of combinations of settings, and the maximum read rate for Frequency is about eight (8) readings per second (R/S). My general configuration settings are:

CONF:FREQ 10000,1, (@111)
ROUT:MON (@111)
ROUT:CHAN:DEL 0, (@111)

In this particular case, I'm only interested in taking frequency measurements on a single channel (111), configured for 0.02 PLC, 4 1/2 digit resolution. I'm executing VISA commands in VB6.

The fastest results seem to be obtained using the "ROUT:MON:DATA?" command. As a point of reference, with the surrounding code in place, but the "ROUT:MON:DATA?" command commented out (not executed), the routine reports a read rate of 972 R/S, so the VB6 code is not the bottleneck. Further, I went as far as changing the Sleep delays (100ms default) and/or eliminating VISA error checks, and while the apparent read rate increases, the real time frequency measurements, discounting repetitive data in the read buffer, is still in the 8-9 R/S range.

I also have the 34970A (GPIB) and the 34980A (GPIB), and both provide somewhat faster frequency measurements (the 34980A being the fastest).

Finally, changing the PLC settings, 0.02 to 10, seem to have no effect on the R/S speed, all consistently in the 8-9 R/S range.

Any insight would be MOST gratefully appreciated.

Thanks, Bill

Update: I also experimented changing the TRIG:COUNT to 20 (20 readings in memory, instead of 1), but in the end, the time it took to take 20 readings still came out to about 8-9 R/S.