After messing around with various projects that require accurate (or at least repeatable) timing, i've finally bitten the bullet and brought a "proper" timer counter, the classic (very classic.... ;-) HP 5335A. Unfortunately it doesn't have the high precision oscillator option, but i was wondering if there are any tweaks / tips / or things i should be aware of with this meter?
It seems quite a popular meter, so i immagine there are quite a few in hobbiest / Amature hands etc!
It ran out of calibration at the end of last year, but i guess now that it's nearly 28 years old it'll be fairly stable??
Nope, the standard XTAL is crappy and will stay crappy forever. (crappy means unstable)
The calibration therefore is near to meaningless.
An ordinary XTAL is good for 1e-6 stability over a day or so , short term stability also not very good.
Temperature coefficient is also bad.
Contrasting that, this instrument resolves about 1ns or 9 digits/sec, therefore an OCXO is required.
Try to get an option 010 = 10811-60111, that is the cheapest one of that series, but after 20+ years, rock stable, i.e. < 1e-10/ day / month.
Should sell for less than 100$. Or get an external GPSDO.
Well, a picture of the interior of your counter, and most important the revision numbers of the PCBs and the complete ser-No prefix of your counter would be great (see below).
Do you already have the opt. 040, that's the GPIB steered front end?
And what about opt. 030, C-Input?
There exist mainly two versions, the elder one covered by manual 05335-90005 (1980, ser prefix #2024) or 05335-90021 (1983, #2224), both online, and the newer version covered by 05335-90044 (1994, #3145A) (available by Artek, I think).
I think, they made severe changes in between, regarding the counting chains. Not sure, anyhow.
Oh yes, and get HP journal 1980-09.
Mine is 2820Axxxx, from 1988, and it contains newer motherboard and opt. 010, 030 (new), 040.
Well I tweaked one electrolytic, which controls the manual gate time, so that I could measure up to 12.5secs, (instead of only 1s), to get 10 digits from the front panel.
Otherwise, GPIB control would do the job, up to 11 digits.
Anyhow, it's a very nice, versatile instrument, but you also need now a GPSDO to enter time-nuts world,as mentioned before
Thunderbolt and Lady Heather make a nice couple..
Frank