FAILED PROJECT IDEA - 53131A Mod Board - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: July 10, 2025, 01:17:14 am
content: I started shooting Part 1 of what I thought would be a nice little project, and then I realised there was a bit of showstopper...

author: rogerggbr
author_rank: Contributor
timestamp: July 10, 2025, 07:18:01 am
content: If you were going to read the RS232, why not just add an additional display external to the box e.g. on top, with as many digits as you like?

author: EEVblog
author_rank: Unknown
timestamp: July 10, 2025, 07:22:13 am
content: Quote from: rogerggbr on July 10, 2025, 07:18:01 amThat was actually my first thought, but then I realised I could fit a tiny 3 digit LED display inside. Such an external display would just be a generic serial port terminal display thing, which is kinda cool in it's own right, but these exist already.

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 10, 2025, 08:46:48 am
content: Yes this is a completely failed idea, for the following reasons:At first, the physical resolution of any (reciprocal and calculating) frequency counter is determined by its Gate Time divided by its time interval resolution.In case of the 53131, it is 1 sec / 1ns = 9 digits/s, and about 1sec/100ps = 10 digits/s for the 53132A.Additionally, they use an averaging method, which gives one extra digit for the same gate time, but that's sort of cheating, and the extra resolution does not give really reliable extra uncertainty, therefore this mode of the 53131/132 is not liked in the time-nuts community.The very old HP5370B, which resolves 10ps single shot time interval, displays real and solid 11 digits/s.Second, a high resolution of more than 9 digits is meaningful only, if your internal timebase is as uncertain.An OCXO is able to provide about 9 digits absolute, meaningful resolution, as it's stable and uncertain to 10^(-9), some special types are even more stable.Then you would need a Rubidium time base, for up to 12 digits resolution, then a GPSDO, or a Cesium clock for 13..14 digits.Here the story of useful applications would end, so 15 digits make no sense in practical applications, even 13 digits is very clumsy to handle.Anyhow, for which application in your lab would you need more than 12 digits at a reasonable 10 sec Gate Time, if you'd be using this old 5370B? Do you have a clock available, that is as stable to this degree, i.e. better than a GPSDO?Frank

author: EEVblog
author_rank: Unknown
timestamp: July 10, 2025, 10:01:29 am
content: Quote from: Dr. Frank on July 10, 2025, 08:46:48 amI have a GPSD rubidium

author: Dr. Frank
author_rank: Super Contributor
timestamp: July 10, 2025, 11:19:12 am
content: Quote from: EEVblog on July 10, 2025, 10:01:29 am=> 12 digits and a 53132A required!

author: EEVblog
author_rank: Unknown
timestamp: July 10, 2025, 12:21:45 pm
content: Quote from: Dr. Frank on July 10, 2025, 11:19:12 amAbout $800 on ebay.Could maybe flip my 53131a locally for the same price for an almost free upgrade

author: Brumby
author_rank: Unknown
timestamp: July 12, 2025, 07:40:27 am
content: Also, your rounding up issue affects more than just the least significant digit...199999999999876would show as200000000000876

author: EEVblog
author_rank: Unknown
timestamp: July 12, 2025, 09:13:12 am
content: Quote from: Brumby on July 12, 2025, 07:40:27 amSo it would!