[time-nuts] HP 5370B

[Magnus Danielson]

From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
Subject: Re: [time-nuts] HP 5370B
Date: Sat, 10 May 2008 17:16:02 +0000
Message-ID: <9243.1210439762 at critter.freebsd.dk>

> In message <27DF566C-9F20-4C0B-A740-22538A826D03 at deriesp.demon.nl>, Henk ten Pi
> erick writes:
> 
> >The 5370 has a resolution of 1ps but the accuracy is much lower. Say  
> >the 20ps stated above.
> 
> And just to make it maddenign difficult, it's not actually 20ps,
> it is:
> 
> 	19.53125 ps [5ns/256]
> 
> or possibly 
> 
> 	19.60783137... ps [5ns/255]
> 
> ...I can never remember which.

You are correct. It's 5 ns / 256. The 20 ps is a handy rought estimate.
It is best viewed as being counted in a 51,2 GHz counting clock.

And to comment on the resolution/accuracy aspectt... they are certainly not the
same.

The resolution is what every steps the hardware will divide the time in.

The precission of those samples can deviate alot, and cross-talk will shift the
time. Biases wiil also show up in TI measures. A calibrator is needed to cancel
those.

The accuracy of the measure also includes the trigger jitter aspect.

Thus, the achieved accuracy and precission is certainly a combined effect of
many error sources. Viewing the shown digit as equalent to the provided
resolution is at best naive. True for some instruments, but not for others.
When in doubt, read the manual.

Cheers,
Magnus