[time-nuts] HP53132A vs SR625
ailer2 at t-online.de
Sun Mar 17 15:47:10 EDT 2013
I just powered on my SR and looked for the offset, when the 10 MHz
reference is connected to the input (at a gate time of 1s without
further averaging). It shows an offset of 0 to 400uHz which should
represent a mean error of 2E-11, while the manual predicts an error of
about 1E-10 (as Said told us, and as my manual tells me). That's within
Unfortunately I don't have a 53132, but the manual of the HP predicts an
error of E-10 - just the same value as with the SR.
If I was a manufacturer of such a counter, I wouldn't show the digits
beneath the predicted error, but SR does: it shows 13 digits. How many
digits does the HP show? Could it be, that the HP shows one or two
digits less at this measurement? With only 11 digits displayed, the SR
wouldn't show any offset, too.
By the way, HP's 100ps isn't the worst case value - that is 500ps.
So, what's the big difference beetween them?
- the predicted error is the same for both (or am I wrong?).
- my SR is within it's specification at 10 MHz (I did the calibration
- the uncertain digits (below 1mHz, in this case) are within the error
spec, and I guess they are uncertain because they come from an analog
circuitry (namely the interpolation circuitry). The statement, that a
counter only has to count zero crossings and nothing else, isn't right
at that point, and that's the case for both,
- and they both have to deal with the analog stuff, such as noise and so on
Again, since I don't have a 53132 I can't compare the counters directly,
I was just a little concerned about a discussion - no offense! - that
compares apples and oranges.
Thank you for a still inspiring discussion!
Am 17.03.2013 20:05, schrieb SAIDJACK at aol.com:
> the calculation is the same, however the numbers are 100ps for 53132A
> versus 350ps, and I have not seen an average systemic offset being displayed on
> any of the 3x 53132A units I use, and I see one on the SR-620. That's why
> I sent it into SRS for calibration, paid the $$$ and got it back with the
> same exact offset and a statement that it is operating within specifications
> so no adjustment is necessary.
> HP manages to show zero error on average, with the digits bouncing back and
> forth. The SRS unit manages to show a hard frequency offset. If I remember
> correctly the SR-620 even shows this offset with it's own reference
> connected to the inputs, the HP does not.
> In a message dated 3/17/2013 11:26:16 Pacific Daylight Time,
> ed_palmer at sasktel.net writes:
> Hi Said,
> That equation looks similar in form to the specs for any counter. What
> are the comparable equations for the 53132A or the 5370(A or B)?
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