Noob question on measuring Allan Deviation on 10 MHz source
List;
OK, I need to measure the stability of a 10 MHz sine-wave source. After
reading a lot of background info on this list and some of the sources that
were referenced, I thought I could get away with a frequency measurement. I
now think I was wrong.
What I have is an Agilent 53230A counter (a pretty capable box - claims 20
ps one-shot resolution in TI mode), a Trimble Thunderbolt, the 10 MHz
oscillator to be measured, and a copy of Stable32. My first effort
involved feeding the Trimble 10 MHz into the counter as its Ext Reference.
I then fed the Trimble 1pps into the Ext Trigger input of the counter and
fed the sinewave 10 MHz signal to be measured into Ch 1 of the counter. I
then captured the frequency reading of the counter every second and stuffed
those numbers into a file. I collected about 20 hours of frequency
readings, but when I imported that into Stable32 and attempted to do an
Allan Dev plot, it didn't look very good - specifically, the sigma numbers
were in the region of 10e-2 to 10e-4.
So, I grabbed another Thunderbolt and attempted to do the same measurement
on it, figuring that everyone (but me) has taken data on a T'bolt, so I
could just look on tvb's site or some such to find proper data on a Tbolt.
Again, the plot didn't look like it should.
Am I going to have to go to time interval measurements to do what I want?
And does this mean I will have to square up my 10 MHz signal to have real
edges?
geo
Once you get the frequencies matched with a fraction of 1 Hz,
I would measure the phase between the 10 MHz source and the
10 MHz from the Trimble.
On 12/14/2011 12:29 PM, George Dubovsky wrote:
List;
OK, I need to measure the stability of a 10 MHz sine-wave source. After
reading a lot of background info on this list and some of the sources that
were referenced, I thought I could get away with a frequency measurement. I
now think I was wrong.
What I have is an Agilent 53230A counter (a pretty capable box - claims 20
ps one-shot resolution in TI mode), a Trimble Thunderbolt, the 10 MHz
oscillator to be measured, and a copy of Stable32. My first effort
involved feeding the Trimble 10 MHz into the counter as its Ext Reference.
I then fed the Trimble 1pps into the Ext Trigger input of the counter and
fed the sinewave 10 MHz signal to be measured into Ch 1 of the counter. I
then captured the frequency reading of the counter every second and stuffed
those numbers into a file. I collected about 20 hours of frequency
readings, but when I imported that into Stable32 and attempted to do an
Allan Dev plot, it didn't look very good - specifically, the sigma numbers
were in the region of 10e-2 to 10e-4.
So, I grabbed another Thunderbolt and attempted to do the same measurement
on it, figuring that everyone (but me) has taken data on a T'bolt, so I
could just look on tvb's site or some such to find proper data on a Tbolt.
Again, the plot didn't look like it should.
Am I going to have to go to time interval measurements to do what I want?
And does this mean I will have to square up my 10 MHz signal to have real
edges?
geo
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--
Chuck Forsberg WA7KGX N2469R caf@omen.com www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
Omen Technology Inc "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430
Hi George --
You can feed frequency data into Stable32, but the documentation doesn't
clearly explain that you need to scale the readings into fractional
frequency using the scaling function in the File/Open dialog. To get
fractional frequency, you divide the results by the nominal frequency,
except that the scaling model in the Stable32 input box allows
multiplication only.
So, for a nominal 10 MHz (or 1e7 Hz) source where the data is in Hz
format (10,000,000.xxx Hz), you would multiply by 1e-7.
But if your counter outputs in MHz format, (10.xxx MHz), that's already
effectively scaled by 1e-6. So you end up using 1e-1 as the multiplier.
I have lost much hair trying to keep this straight; as wonderful as
Stable32 is, the documentation is aimed at people who already know what
they are doing. :-)
73,
John
On 12/14/2011 3:29 PM, George Dubovsky wrote:
List;
OK, I need to measure the stability of a 10 MHz sine-wave source. After
reading a lot of background info on this list and some of the sources that
were referenced, I thought I could get away with a frequency measurement. I
now think I was wrong.
What I have is an Agilent 53230A counter (a pretty capable box - claims 20
ps one-shot resolution in TI mode), a Trimble Thunderbolt, the 10 MHz
oscillator to be measured, and a copy of Stable32. My first effort
involved feeding the Trimble 10 MHz into the counter as its Ext Reference.
I then fed the Trimble 1pps into the Ext Trigger input of the counter and
fed the sinewave 10 MHz signal to be measured into Ch 1 of the counter. I
then captured the frequency reading of the counter every second and stuffed
those numbers into a file. I collected about 20 hours of frequency
readings, but when I imported that into Stable32 and attempted to do an
Allan Dev plot, it didn't look very good - specifically, the sigma numbers
were in the region of 10e-2 to 10e-4.
So, I grabbed another Thunderbolt and attempted to do the same measurement
on it, figuring that everyone (but me) has taken data on a T'bolt, so I
could just look on tvb's site or some such to find proper data on a Tbolt.
Again, the plot didn't look like it should.
Am I going to have to go to time interval measurements to do what I want?
And does this mean I will have to square up my 10 MHz signal to have real
edges?
geo
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John,
I believe the scaling factor was the key. Thanks.
I have v 1.58 of Stable32 and the scaling function now has its own button
and is not in the Open dialog. I'm sure I'm nowhere near out of the woods
yet, so I'm gonna keep your e-mail addy on speed dial ;-)
geo
On Wed, Dec 14, 2011 at 4:19 PM, John Ackermann N8UR jra@febo.com wrote:
Hi George --
You can feed frequency data into Stable32, but the documentation doesn't
clearly explain that you need to scale the readings into fractional
frequency using the scaling function in the File/Open dialog. To get
fractional frequency, you divide the results by the nominal frequency,
except that the scaling model in the Stable32 input box allows
multiplication only.
So, for a nominal 10 MHz (or 1e7 Hz) source where the data is in Hz format
(10,000,000.xxx Hz), you would multiply by 1e-7.
But if your counter outputs in MHz format, (10.xxx MHz), that's already
effectively scaled by 1e-6. So you end up using 1e-1 as the multiplier.
I have lost much hair trying to keep this straight; as wonderful as
Stable32 is, the documentation is aimed at people who already know what
they are doing. :-)
73,
John
On 12/14/2011 3:29 PM, George Dubovsky wrote:
List;
OK, I need to measure the stability of a 10 MHz sine-wave source. After
reading a lot of background info on this list and some of the sources that
were referenced, I thought I could get away with a frequency measurement.
I
now think I was wrong.
What I have is an Agilent 53230A counter (a pretty capable box - claims 20
ps one-shot resolution in TI mode), a Trimble Thunderbolt, the 10 MHz
oscillator to be measured, and a copy of Stable32. My first effort
involved feeding the Trimble 10 MHz into the counter as its Ext Reference.
I then fed the Trimble 1pps into the Ext Trigger input of the counter and
fed the sinewave 10 MHz signal to be measured into Ch 1 of the counter. I
then captured the frequency reading of the counter every second and
stuffed
those numbers into a file. I collected about 20 hours of frequency
readings, but when I imported that into Stable32 and attempted to do an
Allan Dev plot, it didn't look very good - specifically, the sigma numbers
were in the region of 10e-2 to 10e-4.
So, I grabbed another Thunderbolt and attempted to do the same measurement
on it, figuring that everyone (but me) has taken data on a T'bolt, so I
could just look on tvb's site or some such to find proper data on a Tbolt.
Again, the plot didn't look like it should.
Am I going to have to go to time interval measurements to do what I want?
And does this mean I will have to square up my 10 MHz signal to have real
edges?
geo
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