Products > Test Equipment
HP 5335A Timer / Counter - Anything i should know?
Dr. Frank:
--- Quote from: tkamiya on February 19, 2019, 01:36:01 pm ---I have a HP5335A just upgraded with HP10811 oven oscillator. I have GPSDO going to a scope channel 1 and HP5335A clock output going into channel 2. Trigger is set on 1. 20 ns / div.
What's reasonable expectations? So far, I have not been able to completely stop the trace movement. The "slug" is extremely touchy and has some hysteresis. (move slug, remove tuning stick, it goes back a little)
--- End quote ---
I don't know how long GPSDO machine and OCXO are already running.
Anyhow, you can easily trim the OCXO to < 10^-9, i.e. to exactly 10.000 000 00x MHz.
Below, the resolution of the trimmer is too bad.
The metal screw driver you're using also influences the result.
I would apply the 10MHz, or the 1pps from the GPSDO to the A input and simply measure FREQ or PER with longest possible Gate Time, that's about 5sec.
That will give enough resolution to trim to that mentioned limit. I also have described an easy modification of a capacitor to get > 10sec Gate Time, and 10 digits resolution.
The OCXO will usually be stable to around 1^-9 over a longer period of time.
Oh yes, the GPSDO signal itself is quite unstable on these short time scales. 1E-9 at 1sec might be achievable, otherwise use TimeLab and GPIB for better trimming over longer time scale.
Frank
tkamiya:
I should stop here then. I have 10.000,000,00x MHz
My GPDSO has been running for over a month, perhaps few months. I have a redundant setup and results are the same using either or. I'm at a point where mere pressure will change the result.
tkamiya:
This is my 5335A on internal OCXO displaying rubidium source.
A little concerning that OCXO, when measured via 12 digit counter has an upward trend. It has been on for 24 hours already.
0culus:
Upward trend? I guess that's not the picture.
tkamiya:
No, the picture is a "beauty shot"....
I'm not sure what it is, but when monitoring internal clock frequency using GPSDO trained 12 digit counter, I see a very slow upward trend on clock frequency. It's VERY SLOW. But nevertheless, it should not be happening. I'm going to let it run for 24 more hours and see if it continues.
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