[time-nuts] Measuring ADEV for a beginner
I've been reading a lot about ADEV and following the threads on the list, particularly Karen's in-flight thread. What I haven't come across is a simple explanation of the basic setup required to go about collecting the data. John Miles referenced this page http://www.ke5fx.com/tpll.htm, and the simple setup at the bottom of the page looks like a reasonable place to start. Seems that I'd need to acquire a phase detector and build or buy some filters and the amp. I can probably figure that out, but how do I get the data into a PC? Is there a basic hardware and software setup that someone could point me to or recommend? Thanks Anthony ___ 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.
Re: [time-nuts] Measuring ADEV for a beginner
Usually phase detectors (we prefer to call them Time Interval Analysers) have data interfaces (RS232, GPIB, LAN). If you build your own then the interface is up to you: usually an RS232 is the best choice. The software to use: take a look at the Miles' TimeLab www.ke5fx.com/timelab/readme.htm or http://www.thegleam.com/ke5fx/. Of course, in case of the GPIB, you also will need an adapter: GPIB/USB or GPIB/LAN but the less expensive GPIB/RS232 maybe a good choice. On Sat, Nov 1, 2014 at 2:29 PM, Anthony Roby ar...@antamy.com wrote: I've been reading a lot about ADEV and following the threads on the list, particularly Karen's in-flight thread. What I haven't come across is a simple explanation of the basic setup required to go about collecting the data. John Miles referenced this page http://www.ke5fx.com/tpll.htm, and the simple setup at the bottom of the page looks like a reasonable place to start. Seems that I'd need to acquire a phase detector and build or buy some filters and the amp. I can probably figure that out, but how do I get the data into a PC? Is there a basic hardware and software setup that someone could point me to or recommend? Thanks Anthony ___ 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.
Re: [time-nuts] Measuring ADEV for a beginner
what you want to measure is a time-series of either frequency data or phase data. the simplest possible case for a beginner would be to have two clocks with 1-PPS (one pulse per second) outputs, and connect one clock to the start-input and the other to the stop-input of a time-interval counter. If you measure phase, keep the time-interval number to a 5...6 digit number and you don't have to worry too much about the internal time-base of the counter. On Sat, Nov 1, 2014 at 3:29 PM, Anthony Roby ar...@antamy.com wrote: I've been reading a lot about ADEV and following the threads on the list, particularly Karen's in-flight thread. What I haven't come across is a simple explanation of the basic setup required to go about collecting the data. John Miles referenced this page http://www.ke5fx.com/tpll.htm, and the simple setup at the bottom of the page looks like a reasonable place to start. Seems that I'd need to acquire a phase detector and build or buy some filters and the amp. I can probably figure that out, but how do I get the data into a PC? Is there a basic hardware and software setup that someone could point me to or recommend? Thanks Anthony ___ 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.
Re: [time-nuts] Measuring ADEV for a beginner
Anthony, On 11/01/2014 02:29 PM, Anthony Roby wrote: I've been reading a lot about ADEV and following the threads on the list, particularly Karen's in-flight thread. What I haven't come across is a simple explanation of the basic setup required to go about collecting the data. John Miles referenced this page http://www.ke5fx.com/tpll.htm, and the simple setup at the bottom of the page looks like a reasonable place to start. Seems that I'd need to acquire a phase detector and build or buy some filters and the amp. I can probably figure that out, but how do I get the data into a PC? Is there a basic hardware and software setup that someone could point me to or recommend? The time-interval counter, such as HP5370 or SR620, get started (channel 1) by a reference clock, such as 1 PPS and is then stopped (channel 2) by signal under test. The counter is typically read out through GPIB, even if some counters have serial interface and maybe even USB or Ethernet for really new (or retro-fitted), and the recommended path is to get a GPIB to USB interface for instance. Then use John Miles TimeLab. Cheers, Magnus ___ 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.
Re: [time-nuts] Measuring ADEV for a beginner
Hi The problem with setting up to measure any of this stuff is that it’s *very* dependent on the gear you have. There’s no big surprises below. It’s all “spend more money and have fewer things to figure out”. First you need a way to measure frequency out of your mixer (there are LOTS of ways …): If you grab a HP 5334 or HP 5335 to measure the frequency or time, you need to get the data out via GPIB. That’s a project by it’s self. If you grab a HP 53131 or CNT 90 to measure the frequency, you can use a serial port. One less project, way more money. If you grab a HP 5371, you just push a button and it pops up an ADEV plot. Less money than a 53131 (usually). It’s a bit limited on the range it will do ADEV over. If you grab a brand new Symmetricom Time Pod, you spend (gulp!!) a bit more. You can now do measurements easily over it’s frequency range. (If you can afford that option - can I come play at your house ?) Yes each of these is it’s own little rabbit hole to wander down and each has it’s own issues. Now you need a reference: GPSDO’s have their fans, they often have spurs and other “crud” on the output. They do have very good long term stability. OCXO’s are often pretty quiet and spur free. You need some way to calibrate them for really long term stuff. Rb’s come in a wide range of sizes and costs. Some are better than others. Their ADEV at 1 second often not as good as an OCXO. Cs standards and Hydrogen masers are (to me) in the same cost category as exotic test gear above. Fine for a company, not quite so easy for a basement guy. Again each of these is a bit of a project by it’s self. Often it turns into a “a couple of these and a couple of those” sort of solution. You only know something is right if you have another one to compare it to. Now you have some gear. Let’s ignore building the mixer board and assume that’s taken care of already. Now you need software: TimeLab is free and it will interface with many of the counters you might be using. It does all the math for you and puts up pretty plots. Highly recommended. There are other free software packages out there. Stable32 is another commonly used program. You need to get the data out of the counter before you can use it. There are other paid programs out there, Stable 32 is the best of the bunch. An Excel spread sheet is indeed another option. The ADEV math is *not* very complicated. Excel can do it all very easily. Getting data out of the counter could be a terminal program sort of thing (serial port) or something more complex (GPIB). In both cases there are a number of programs to pick between. With software, things like what computer and operating system you have will influence your choices. I’m a Mac person, but I also run Linux, Windows, FreeBSD and a few other things as needed. Most people have a favorite …. So, that’s the quick and dirty start to the “quick ADEV setup” process. There are: 4 counter like things X 4 reference ideas X (at least 4 mixer approaches) X (way more than) 4 software options = 256 paths you could follow. That’s quite a few, and many of them would be utter nonsense. Even pruning out the ones are unlikely to ever be followed, you still have lots. Here’s one: 1) Drive your “known good” reference OCXO into a Minicircuits RPD-1 mixer. 2) Drive your “device under test” into the other side of the RPD-1 3) Amplify and limit the output with a couple of OP-37 op amps running off of +/-15V. first stage is an amp with high pass and low pass sections second stage is an inverter / limiter (back to back diodes in a normal op amp inverter). third stage is same as the second you might (or might not) want a fourth stage 4) Feed the +/- 0.7 V limited output into a 5335 (DC couple the input) in talk only mode 5) Hook up the 5335 to a National Instruments GPIB card on a PC 6) Run a Visual Basic routine to grab the outputs and write them to a text file. 7) Process the text file with Excel. Use the ADEV formula from the original NIST papers. There have been a *lot* of OCXO’s tested that way in many different factories over a couple of decades. (Yes, it’s probably easier these days to substitute Time Lab for steps 6 and 7). Is it the ideal or perfect way to do it? Certainly not. It is one of many simple ways it can be done. Even this simple way has two forks in it (TimeLab or not). It also has a few features like a know good OCXO and the undocumented circuit on the output of the RPD-1. Quick, simple and pretty much useless to you. It’s my favorite way to do it, but that really should not make it your favorite. What to do? It’s really a multi part process. Break each section down and address it separately. You *do* have a goal in mind, but get each chunk running by it’s self. Do simple verifications each step of the way. Tie it all together at the end. Accept that you *will* spend
Re: [time-nuts] Measuring ADEV for a beginner
Thanks for this. I should have said that I have a Racal-Dana 1992 counter (with GPIB) and I have an Isotemp OCXO134-10, so its sounds like I just need the opamps, an RPD-1 and a GPIB-USB interface plus some software. I'll do a bit more digging around and see if I can get the GPIB up and running in the next couple of weeks. Anthony -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Saturday, November 01, 2014 3:18 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Measuring ADEV for a beginner Hi The problem with setting up to measure any of this stuff is that it ??s *very* dependent on the gear you have. There ??s no big surprises below. It ??s all ??spend more money and have fewer things to figure out ??. First you need a way to measure frequency out of your mixer (there are LOTS of ways ? ): If you grab a HP 5334 or HP 5335 to measure the frequency or time, you need to get the data out via GPIB. That ??s a project by it ??s self. If you grab a HP 53131 or CNT 90 to measure the frequency, you can use a serial port. One less project, way more money. If you grab a HP 5371, you just push a button and it pops up an ADEV plot. Less money than a 53131 (usually). It ??s a bit limited on the range it will do ADEV over. If you grab a brand new Symmetricom Time Pod, you spend (gulp!!) a bit more. You can now do measurements easily over it ??s frequency range. (If you can afford that option - can I come play at your house ?) Yes each of these is it ??s own little rabbit hole to wander down and each has it ??s own issues. Now you need a reference: GPSDO ??s have their fans, they often have spurs and other ??crud ?? on the output. They do have very good long term stability. OCXO ??s are often pretty quiet and spur free. You need some way to calibrate them for really long term stuff. Rb ??s come in a wide range of sizes and costs. Some are better than others. Their ADEV at 1 second often not as good as an OCXO. Cs standards and Hydrogen masers are (to me) in the same cost category as exotic test gear above. Fine for a company, not quite so easy for a basement guy. Again each of these is a bit of a project by it ??s self. Often it turns into a ??a couple of these and a couple of those ?? sort of solution. You only know something is right if you have another one to compare it to. Now you have some gear. Let ??s ignore building the mixer board and assume that ??s taken care of already. Now you need software: TimeLab is free and it will interface with many of the counters you might be using. It does all the math for you and puts up pretty plots. Highly recommended. There are other free software packages out there. Stable32 is another commonly used program. You need to get the data out of the counter before you can use it. There are other paid programs out there, Stable 32 is the best of the bunch. An Excel spread sheet is indeed another option. The ADEV math is *not* very complicated. Excel can do it all very easily. Getting data out of the counter could be a terminal program sort of thing (serial port) or something more complex (GPIB). In both cases there are a number of programs to pick between. With software, things like what computer and operating system you have will influence your choices. I ??m a Mac person, but I also run Linux, Windows, FreeBSD and a few other things as needed. Most people have a favorite ? . So, that ??s the quick and dirty start to the ??quick ADEV setup ?? process. There are: 4 counter like things X 4 reference ideas X (at least 4 mixer approaches) X (way more than) 4 software options = 256 paths you could follow. That ??s quite a few, and many of them would be utter nonsense. Even pruning out the ones are unlikely to ever be followed, you still have lots. Here ??s one: 1) Drive your ??known good ?? reference OCXO into a Minicircuits RPD-1 mixer. 2) Drive your ??device under test ?? into the other side of the RPD-1 3) Amplify and limit the output with a couple of OP-37 op amps running off of +/-15V. first stage is an amp with high pass and low pass sections second stage is an inverter / limiter (back to back diodes in a normal op amp inverter). third stage is same as the second you might (or might not) want a fourth stage 4) Feed the +/- 0.7 V limited output into a 5335 (DC couple the input) in talk only mode 5) Hook up the 5335 to a National Instruments GPIB card on a PC 6) Run a Visual Basic routine to grab the outputs and write them to a text file. 7) Process the text file with Excel. Use the ADEV formula from the original NIST papers. There have been a *lot* of OCXO ??s tested that way in many different factories over a couple of decades. (Yes, it ??s probably easier these days to substitute Time Lab for steps 6 and 7). Is it the ideal
Re: [time-nuts] Measuring ADEV for a beginner
Thanks - seems that I should be able to do this with my Racal-Dana 1992 counter. Anthony -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Saturday, November 01, 2014 1:29 PM To: time-nuts@febo.com Cc: mag...@rubidium.se Subject: Re: [time-nuts] Measuring ADEV for a beginner Anthony, On 11/01/2014 02:29 PM, Anthony Roby wrote: I've been reading a lot about ADEV and following the threads on the list, particularly Karen's in-flight thread. What I haven't come across is a simple explanation of the basic setup required to go about collecting the data. John Miles referenced this page http://www.ke5fx.com/tpll.htm, and the simple setup at the bottom of the page looks like a reasonable place to start. Seems that I'd need to acquire a phase detector and build or buy some filters and the amp. I can probably figure that out, but how do I get the data into a PC? Is there a basic hardware and software setup that someone could point me to or recommend? The time-interval counter, such as HP5370 or SR620, get started (channel 1) by a reference clock, such as 1 PPS and is then stopped (channel 2) by signal under test. The counter is typically read out through GPIB, even if some counters have serial interface and maybe even USB or Ethernet for really new (or retro-fitted), and the recommended path is to get a GPIB to USB interface for instance. Then use John Miles TimeLab. Cheers, Magnus ___ 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.
Re: [time-nuts] Measuring ADEV for a beginner
ar...@antamy.com said: I'll do a bit more digging around and see if I can get the GPIB up and running in the next couple of weeks. I've been happy with the ProLogic GPIB-USB gizmo. https://www.sparkfun.com/products/549 It took some fiddling to get going, but I like chasing that sort of thing. http://www.megapathdsl.net/~hmurray/hacks/probe.c -- These are my opinions. I hate spam. ___ 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.
Re: [time-nuts] Measuring ADEV for a beginner
That will work as a starting-point. When you look at your ADEV plot, you will notice a 1/tau curve for the lower taus, that is due to your counters limitations. If you need to go below that, you need a better counter, but for the moment you should start believe the plot as it flattens out, that has more to do with your signal, unless that is the same as your reference or a very high measurement floor of the counter. A good test is to split your reference into the start and stop inputs, and then measure the amount of noise you have. Preferably with a slightly longer cable to the stop channel. This will give you the noise floor of the counter, for that signaltype and trigger-point. There are ways to improve things if your noise is higher than the single-shot resolution, as you read out the ADEV at tau=1s. Cheers, Magnus On 11/01/2014 09:43 PM, Anthony Roby wrote: Thanks - seems that I should be able to do this with my Racal-Dana 1992 counter. Anthony -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Saturday, November 01, 2014 1:29 PM To: time-nuts@febo.com Cc: mag...@rubidium.se Subject: Re: [time-nuts] Measuring ADEV for a beginner Anthony, On 11/01/2014 02:29 PM, Anthony Roby wrote: I've been reading a lot about ADEV and following the threads on the list, particularly Karen's in-flight thread. What I haven't come across is a simple explanation of the basic setup required to go about collecting the data. John Miles referenced this page http://www.ke5fx.com/tpll.htm, and the simple setup at the bottom of the page looks like a reasonable place to start. Seems that I'd need to acquire a phase detector and build or buy some filters and the amp. I can probably figure that out, but how do I get the data into a PC? Is there a basic hardware and software setup that someone could point me to or recommend? The time-interval counter, such as HP5370 or SR620, get started (channel 1) by a reference clock, such as 1 PPS and is then stopped (channel 2) by signal under test. The counter is typically read out through GPIB, even if some counters have serial interface and maybe even USB or Ethernet for really new (or retro-fitted), and the recommended path is to get a GPIB to USB interface for instance. Then use John Miles TimeLab. Cheers, Magnus ___ 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. ___ 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.
