Frequency counter questions
Hello, I would like to find a person that would be able to answer some frequency counter questions I have.
Basically, I am thinking of building my own using one of the high end STM32F7 boards as the counter. I would like it to count reliably to 12 digits (e.g. 30,000,000.001x hz). I am not worried about input conditioning as I have a circuit that is suitable for my needs. Most of my questions have to do with using a prescaler on the front (divide by N where what is N) to get to the desired resolution when using multiples of the PPS coming from my GPSDO. Gate times could be as long as needed to get the resolution. So what prescaler do I need and what gate time is required are the first two questions. I suggest if someone is willing to help that they either reply here with an email address or send a note to meters at hanler dot com. This is for my own non-commercial use.
Thanks!
Jerry
Hi Jerry,
Consider building a fractional frequency counter. In it, you will
measure both the time and number of input events.
Consider building a time-stamping counter, in which post-processing can
combine multiple timestamps (each holding time and event counters), as
post-processing can help to improve resolution.
Consider how you can achieve highest time resolution of your start time
and stop time, i.e. time-stamping.
Cheers,
Magnus
On 04/23/2017 09:14 AM, Jerry Hancock wrote:
Hello, I would like to find a person that would be able to answer some frequency counter questions I have.
Basically, I am thinking of building my own using one of the high end STM32F7 boards as the counter. I would like it to count reliably to 12 digits (e.g. 30,000,000.001x hz). I am not worried about input conditioning as I have a circuit that is suitable for my needs. Most of my questions have to do with using a prescaler on the front (divide by N where what is N) to get to the desired resolution when using multiples of the PPS coming from my GPSDO. Gate times could be as long as needed to get the resolution. So what prescaler do I need and what gate time is required are the first two questions. I suggest if someone is willing to help that they either reply here with an email address or send a note to meters at hanler dot com. This is for my own non-commercial use.
Thanks!
Jerry
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Up to the point that, to get 1milliHz resolution, you have to wait
1000 seconds (without the prescaler)? If you have a prescaler then it
will be N*1000 seconds...
On Sun, Apr 23, 2017 at 9:14 AM, Jerry Hancock jerry@hanler.com wrote:
Hello, I would like to find a person that would be able to answer some frequency counter questions I have.
Basically, I am thinking of building my own using one of the high end STM32F7 boards as the counter. I would like it to count reliably to 12 digits (e.g. 30,000,000.001x hz). I am not worried about input conditioning as I have a circuit that is suitable for my needs. Most of my questions have to do with using a prescaler on the front (divide by N where what is N) to get to the desired resolution when using multiples of the PPS coming from my GPSDO. Gate times could be as long as needed to get the resolution. So what prescaler do I need and what gate time is required are the first two questions. I suggest if someone is willing to help that they either reply here with an email address or send a note to meters at hanler dot com. This is for my own non-commercial use.
Thanks!
Jerry
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
Counting 12 digits is relatively easy, if that is the only constraint. Bring your “signal” into one of the
timer clock inputs on the MCU. If your “signal” is 10 MHz that will be simple. If it’s 30 GHz it will be
more difficult.
10 MHz gives you 7 digits a second. To get to 12 digits, you need 100,000 seconds. Roughly speaking,
your counter “gate time” would be one day. If your input is 1 MHz, your “gate time” would be 10 days.
My guess is that there is a disconnect between what you want to do and what I’m hearing you want to do.
====
If you want to do something like the 53131 or even the 5335, you will need something a bit different
than the F7 to do it. They are wonderful MCU’s but not really fast enough to do the fancy stuff.
Bob
On Apr 23, 2017, at 3:14 AM, Jerry Hancock jerry@hanler.com wrote:
Hello, I would like to find a person that would be able to answer some frequency counter questions I have.
Basically, I am thinking of building my own using one of the high end STM32F7 boards as the counter. I would like it to count reliably to 12 digits (e.g. 30,000,000.001x hz). I am not worried about input conditioning as I have a circuit that is suitable for my needs. Most of my questions have to do with using a prescaler on the front (divide by N where what is N) to get to the desired resolution when using multiples of the PPS coming from my GPSDO. Gate times could be as long as needed to get the resolution. So what prescaler do I need and what gate time is required are the first two questions. I suggest if someone is willing to help that they either reply here with an email address or send a note to meters at hanler dot com. This is for my own non-commercial use.
Thanks!
Jerry
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Assuming you are counting every cycle with no pre-scaler and can't measure
the period, the answer is easy.
If you want to measure Hz then the gate needs to be 1 second. If you want
to measure too 0.1 Hz then you need a 10 second gate. In your case 0.001
Hz you need to count for 1,000 seconds.
If you use a prescaler let's say it is a "divide by N" then you multiply
the gate time by N.
If the frequency is high and you want to measure to .001 Hz then you need a
really large maximum count and will overflow a 32 bit integer You want 12
digits so you need to use a 64 bit integer counter.
The STM32 has some pre-scalers built in and a built in counter too, I
think. I don't know what their maximum speed is. You don't need the
compute power is an STM32 but "why not" as they cost only $12, I use the
Nucleo boards and mbed.
The problem with counting to 12 digits is that you are only measuring the
average frequency over a very long interval. The signal is likely not that
stable. Lets say during that 10 second gate the signal was DC or zero Hz
for 5 seconds then went to 2 MHz. You meter would read 1.000 MHz but the
signal was NEVER 1 MHz.
The OTHER way to measure frequency is harder but faster. You measure the
period. A perfect meter could mere the unknown frequency in one cycle.
It would not be an average. But there are no perfect meters.
On Sun, Apr 23, 2017 at 12:14 AM, Jerry Hancock jerry@hanler.com wrote:
Hello, I would like to find a person that would be able to answer some
frequency counter questions I have.
Basically, I am thinking of building my own using one of the high end
STM32F7 boards as the counter. I would like it to count reliably to 12
digits (e.g. 30,000,000.001x hz). I am not worried about input
conditioning as I have a circuit that is suitable for my needs. Most of my
questions have to do with using a prescaler on the front (divide by N where
what is N) to get to the desired resolution when using multiples of the PPS
coming from my GPSDO. Gate times could be as long as needed to get the
resolution. So what prescaler do I need and what gate time is required are
the first two questions. I suggest if someone is willing to help that they
either reply here with an email address or send a note to meters at hanler
dot com. This is for my own non-commercial use.
Thanks!
Jerry
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California
At that resolution, you need a very accurate and stable Time Base.
A GPSDO may not be good enough for 10 e12 measurements.
73, Dick, W1KSZ
Sent from Outlookhttp://aka.ms/weboutlook
From: time-nuts time-nuts-bounces@febo.com on behalf of Jerry Hancock jerry@hanler.com
Sent: Sunday, April 23, 2017 12:14:49 AM
To: Discussion of precise time and frequency measurement
Cc: meters@hanler.com
Subject: [time-nuts] Frequency counter questions
Hello, I would like to find a person that would be able to answer some frequency counter questions I have.
Basically, I am thinking of building my own using one of the high end STM32F7 boards as the counter. I would like it to count reliably to 12 digits (e.g. 30,000,000.001x hz). I am not worried about input conditioning as I have a circuit that is suitable for my needs. Most of my questions have to do with using a prescaler on the front (divide by N where what is N) to get to the desired resolution when using multiples of the PPS coming from my GPSDO. Gate times could be as long as needed to get the resolution. So what prescaler do I need and what gate time is required are the first two questions. I suggest if someone is willing to help that they either reply here with an email address or send a note to meters at hanler dot com. This is for my own non-commercial use.
Thanks!
Jerry
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On Sun, Apr 23, 2017 at 7:38 AM, Bob kb8tq kb8tq@n1k.org wrote:
If you want to do something like the 53131 or even the 5335, you will need
something a bit different
than the F7 to do it. They are wonderful MCU’s but not really fast enough
to do the fancy stuff.
Yes, But I assume he is not going to do the actual counting in software.
He will likely be using the CPU to set and read some registers and control
the user interface.
The time stamping idea is not bad. But today you do NOT need to "post
process". Your little processor could do this in nearly real-time and
you'd have results on the screen in seconds.
--
Chris Albertson
Redondo Beach, California
Hi
On Apr 23, 2017, at 2:43 PM, Chris Albertson albertson.chris@gmail.com wrote:
On Sun, Apr 23, 2017 at 7:38 AM, Bob kb8tq kb8tq@n1k.org wrote:
If you want to do something like the 53131 or even the 5335, you will need
something a bit different
than the F7 to do it. They are wonderful MCU’s but not really fast enough
to do the fancy stuff.
Yes, But I assume he is not going to do the actual counting in software.
Except that’s not what he said he was trying to do. Thus the confusion and attempt
to clarify what he’s trying to do. We now have a half dozen people who are equally
confused about the task and no further input from the only person who actually
knows what he’s trying to do. If indeed you have registers and the like, then they
are probably in an FPGA. If you already have an FPGA doing the high speed stuff,
the need for the F7 is even more questionable. Yes it’s a $12 or so chip, what needs
to be done can be done with a $2 chip. Not only is would it be cheaper. It likely
would be faster and easier to get working.
Bob
He will likely be using the CPU to set and read some registers and control
the user interface.
The time stamping idea is not bad. But today you do NOT need to "post
process". Your little processor could do this in nearly real-time and
you'd have results on the screen in seconds.
--
Chris Albertson
Redondo Beach, California
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
On Apr 23, 2017, at 12:43 PM, Richard Solomon w1ksz@outlook.com wrote:
At that resolution, you need a very accurate and stable Time Base.
A GPSDO may not be good enough for 10 e12 measurements.
If buy some truly strange chance, this is a 100,000 second gate time exercise
(which I very much doubt) …. a GPSDO may well be just fine for that level of performance.
It would need to have a good antenna location and to be in a reasonable environment.
Other than that an OCXO based device should not have a lot of trouble after a
couple days warmup.
If somehow this morphs into a three sigma at 1x10^-12 accuracy at 1 second project
then indeed, a GPSDO is not in any way going to be adequate to the task. You can pretty well
extend that to 10 and 100 seconds without much chance of being contradicted. You also
aren’t going to get that sort of accuracy at 1 second without doing a lot of heavy lifting
counter hardware wise. The MCU choice becomes a very minor point on a fairly
long list.
Bob
73, Dick, W1KSZ
Sent from Outlookhttp://aka.ms/weboutlook
From: time-nuts time-nuts-bounces@febo.com on behalf of Jerry Hancock jerry@hanler.com
Sent: Sunday, April 23, 2017 12:14:49 AM
To: Discussion of precise time and frequency measurement
Cc: meters@hanler.com
Subject: [time-nuts] Frequency counter questions
Hello, I would like to find a person that would be able to answer some frequency counter questions I have.
Basically, I am thinking of building my own using one of the high end STM32F7 boards as the counter. I would like it to count reliably to 12 digits (e.g. 30,000,000.001x hz). I am not worried about input conditioning as I have a circuit that is suitable for my needs. Most of my questions have to do with using a prescaler on the front (divide by N where what is N) to get to the desired resolution when using multiples of the PPS coming from my GPSDO. Gate times could be as long as needed to get the resolution. So what prescaler do I need and what gate time is required are the first two questions. I suggest if someone is willing to help that they either reply here with an email address or send a note to meters at hanler dot com. This is for my own non-commercial use.
Thanks!
Jerry
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Confusion comes about because there is a ton of on-chip hardware an
addition to the CPU. An edge detector, prescaller and a few hardware
counters on the STM32. So I said he'd likely not be actually counting in
software but just setting up the desired tiger condition, loading the
prescaler then letting it run for a gate interval and finally reading out
the count. The hardware is good for some tens of MHz. But you really
have to be careful in your programming to get this exactly right. Easy to
by off by one.
The chip has all kinds of other devices that greatly off load the CPU for
example making PWM outputs.
But you are right, we don't know what the OP wants to do. Is he a ham what
needs to monitor the output of a transmitter and is this HF or microwave.
We's need to know the real world use case in order to suggest a solution.
On Sun, Apr 23, 2017 at 12:48 PM, Bob kb8tq kb8tq@n1k.org wrote:
Yes, But I assume he is not going to do the actual counting in software.
Except that’s not what he said he was trying to do. Thus the confusion
and attempt
to clarify what he’s trying to do. We now have a half dozen people who are
equally
confused about the task and no further input from the only person who
actually
knows what he’s trying to do. If indeed you have registers and the like,
then they
are probably in an FPGA. If you already have an FPGA doing the high speed
stuff,
the need for the F7 is even more questionable. Yes it’s a $12 or so chip,
what needs
to be done can be done with a $2 chip. Not only is would it be cheaper. It
likely
would be faster and easier to get working.
Bob
He will likely be using the CPU to set and read some registers and
control
the user interface.
The time stamping idea is not bad. But today you do NOT need to "post
process". Your little processor could do this in nearly real-time and
you'd have results on the screen in seconds.
--
Chris Albertson
Redondo Beach, California
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California