[time-nuts] Re: Vernier interpolation

[Bob Camp]

Hi

There are now a range of TDC chips out. They come from a lot of sources. It tends to be
a “you get what you pay for” sort of thing. If your budget can fit something in the $20 to $30
range, you are into the same sort of timing resolution as the 5370. You hit the “darn close” 
range before you get to $10. 

Cost tends to make these the “go to” answer for designs these days. There are a number of 
“home made” counters out there that use these chips. The TAPR TICC is one famous example:

https://tapr.org/product/tapr-ticc/

There is a *lot* more to a full up bench instrument like the 5370 than just the TDC section. You
very much do not get “all of that” for your $30. 

Bob

> On Jul 14, 2025, at 2:23 PM, Tom Verbeure via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I bought myself an HP 5370A yesterday at the electronics flea market. Smoke
> came out of it after plugging it in (which means I bought myself a good
> amount of entertainment for just $40), but it made me study the dual
> Vernier method of interpolation.
> 
> I understand how it works, but I've been wondering if this is a technique
> that continues to be used or has the availability of fast and
> high-precision ADCs resulted in it being replaced by the voltage slope
> interpolation method that's used by the SR620?
> 
> According to the August 1978 edition of HP Journal, the 5370A is using a
> custom hybrid with 5GHz transistors. I'm wondering if anyone has ever tried
> making their own TI counter using the Vernier method? (TBH, I don't think
> I've ever seen anyone build their own TI counter using slope interpolation,
> but at least high precision ADCs are available on Digikey...)
> 
> Tom
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