[time-nuts] 53132A counter slow frequency update

Jose Camara camaraq1 at quantacorp.com
Thu Jun 30 20:27:42 UTC 2011


Bob:

	Perhaps different firmware revisions behave differently? Mine has
4613 and doesn't miss a single gate period when switching up or down - I
went from 80MHz down to 1MHz and even 100Hz, without confounding the meter.

Jose

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bob Camp
Sent: Thursday, June 30, 2011 9:34 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] 53132A counter slow frequency update

Hi

The 53132 and 53131 behave oddly when the frequency is dropped. Apparently
they do some sort of pre-scaling thing in their firmware. When you drop
frequency 100:1 at a 1 second gate time it indeed can take quite a while for
it to figure out what's going on.

Simple fix - poke the run button when you change frequency. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jose Camara
Sent: Thursday, June 30, 2011 11:21 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] 53132A counter slow frequency update

John:

	I'd run the performance tests from the service manual (available at
Agilent.com). You mentioned rear inputs, option 060, and that might be a
clue. Option 060 has a 15dB lower sensitivity specification, and in the
service manual it specifically states to not use front input when you have
rear ones installed (the rear connectors are simply a BNC with a short cable
soldered to the board in parallel to the front PCB-mount BNCs).

--From the Service Manual-------------------------------
DO NOT test the front terminals if rear terminals are installed. The front
terminal performance is not specified when the rear terminals are installed.
--------------------------------------------------------

	If you don't need the rear panel inputs, I'd get rid of them. It
seems like an afterthought option HP didn't really consider when designing
the counter, not meant for dual inputs, just moving the legal input to the
back.

	Now, 10" of coax as a stub shouldn't hurt you in the low MHz region,
so it doesn't explain your issue.


	Another thing I found out is that the statement I made in my last
email, that the 53132A always power up at a factory default state, is only
true for firmware revisions 3622 and above. Older revs would apparently save
to register 0 the current state before a recall operation - I can see how
that led to confusion and was eliminated.

Jose

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Pease
Sent: Wednesday, June 29, 2011 5:06 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] 53132A counter slow frequency update

HI Jose,
 
Thank you for the ideas.
 
I am using a Tektronix AFG 3102 DDS generator which works up to 100 MHz.
 
The counter firmware version is 3646.
 
I tried  sine wave amplitudes between 70 mV and 1V ptp. The waveforms looked
good on the oscilloscope. I did notice that the Hi-Z front panel input will
attenuate the input signal quite a bit unless I terminate the rear panel
inputs in 50 Ohms.
 
I tried different thresholds and gate times and I still get the same
behavior.
 
If I flip between 100 MHz and 1MHz 20 times, there will be a delay in
updating the 1 MHz measurement about 5 times.
 
I ran each of the self test routines and they all passed.
 
Both low frequency input channels show this behavior, as well as the 12.4
GHz input (input frequency switched between 12 GHz abnd 200 MHz).
 
 
A coworker suggested that the counter might be slower in updating to a new
lower frequency because its interleaves counting edges and would be thrown
off if the new edge rate was much slower.
 
The fact that your counter works as expected casts doubt on this
possibility.
 
 
Any suggestions will be greatly appreciated.
 
John Pease
 
 
 
 
Check your cable, or better yet, look at the input signal with a
oscilloscope. Something is fishy (missing return plus AC couple, too low
amplitude, etc.).

I used a 33250 generator at 50mVrms and tried going from 80MHz down to 1MHz,
even 100Hz and it changed the very next gate period every time (one period
had partial counts, of course).

The 53132A doesn't have the 'green button' that presets it to a known state,
but it always powers up in the default state. 

Your signal might need some special handling - sensitivity, coupling,
termination?

Finally, if the counter is an 'eBay special', it might be bad. Run self-test
and follow confidence tests from service manual.

Jose


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Pease
Sent: Tuesday, June 28, 2011 11:07 AM
To: time-nuts at febo.com
Subject: [time-nuts] 53132A counter slow frequency update






Hello,
?
My new to me counter has a strange response when I change the input
frequency. With the gate set to 1s, I can measure 100 MHz with plenty of
digits. Then I change the frequency to 1 MHz and it takes several seconds to
almost a minute for the display to change from 100 MHz to 1 MHz. The delay
only occurs when I lower the input frequency quite a bit; 100?MHz to 10 MHz
changes are displayed within 2 gate times.?When I increase the frequency
form 1 MHz to 100 MHz I always get the correct display after two gate times.
This delay is proportional to the gate time; the updating is 10 times faster
with 0.1 s gate time.
?
Is this behavior typical for this counter?
?
Thank you
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