Re: [time-nuts] new tdc from Texas
On Thu, 05 Mar 2015 01:27:23 + Angus wrote: > I've not seen any mention of anything other than the TDC1000. > > I was a bit surprised that they went down the less-integrated route > and separated the TDC, but it turns out that for a lot of the sort of > things they designed it for, a uC provides good enough timing itself, > and no extra TDC is needed at all. I think the main application TI intended it for is for ultrasonic flow meeters (like [1]). There you have quite small and bounded start-stop delays. With this they can get into the growing electronics for low energy building market. In contrast to that, the Acam devices seem to be general purpose TDCs Attila Kinali [1] http://www.shk-profi.de/imgs/52579203_0d4dd378d4.jpg -- < _av500_> phd is easy < _av500_> getting dsl is hard ___ 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] AVAR <-> S_Y conversion
Hello time-nuts community, I hope this is the right place for the following question :) I'm dealing with the simulation of powerlaw noise, and I stumbled upon something I cannot explain when I tried out some formulas of IEEE 1139 [1]: According to Table B.2 in [1] the one-sided power spectral density of fractional frequency data and the Allan variance of this data can be related as follows: PSD of FFD: S_y(f) = h_alpha * f1^alpha AVAR:Sigma_y(Tau) = K * h_alpha * f ^ x where K and x depend on the type of noise (alpha). For your convenience I made a screenshot of the formulas I'm referring to: http://postimg.org/image/6qcx3ggu9/ I have generated data sets with simulated powerlaw noise for different values of alpha, and did the following for each of these noise vectors: *) Calculated and plotted the Allan Variance *) Used to formulas of [1] to calculate h_alpha *) Calculated and plotted the FFD-PSD (the PSD plot is averaged the get better visual results) *) Added colored lines to both plots according to the calculated h_alpha values I would have expected that the colored lines would match each plot. However, this is only the case for White PM, Flicker PM, White FM and Flicker FM noise. To my surprise the calculated line for random walk noise does not match the PSD plot. For the random walk noise the expected line is off by a factor of exactly 2 from the calculated plot, and I don't know how to explain this behavior. I supposed that maybe the factor A is twice as large as it should be, and thus I searched in other powerlaw noise publications for different formulas. However, as far as I can see they agree with the definition given in [1]. I could only find one paper with another definition: [2] In that other paper A is defined as 2 pi^2/6 instead of 2 pi^2/3 (equation 24). Using this definition would result in a plot that matches what I would have expected. These are the graphs I'm referring to: White PM: http://postimg.org/image/fk059s243/full/ Flicker PM: http://postimg.org/image/6q71l03cp/full/ White FM: http://postimg.org/image/mxhxeszqx/full/ Flicker FM: http://postimg.org/image/3vzpj7jmf/full/ Random Walk: http://postimg.org/image/hxad6okwv/full/ <-- the bad guy Does anyone know the reason for the behavior I see? best regards, Wolfgang Wallner PS: I tried to keep this mail short. If I have left out any information that would be useful feel free to ask, please :) [1] 1139-2008 - IEEE Standard Definitions of Physical Quantities for Fundamental Frequency and Time Metrology [2] Gaderer, et al - Achieving a Realistic Notion of Time in Discrete Event Simulation ___ 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] FYI HP 53131A counter
Greetings to the time nuts, I recently purchased this counter from Ebay. I don't have any connection with the seller. It looks brand new. It is the only HP item that I now have that is in current production. Ebay Item: 271777486308 Keep the time, Gordon WA4FJC ___ 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] new tdc from Texas
379998 <379...@qq.com> writes: > Hi > > The spec is similar with TDC-GP22. In double-res mode, the > resolution is 45ps, the stdev is 35ps. This unit is 55ps and > 35ps. Not sure when the sample chip is ready. The TSSOP package is > much more friendly to homebrew guys. > Indeed this looks like quite an interesting device. I'm not sure I understand how it is able to approach timing resolution comparable to that of the THS788 yet at a fraction of the power. The sample rate is evidently quite limited. Is this just a function of the ring oscillator duty cycle being much smaller? Also, does anyone understand the reason behind the 12ns minimum measurement time? Cheers, - Ben pgpks0OEnyQ82.pgp Description: PGP signature ___ 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] R: FYI HP 53131A counter
>Greetings to the time nuts, > >I recently purchased this counter from Ebay. I don't have any connection >with the seller. It looks brand new. It is the only HP item that I now >have that is in current production. > >Ebay Item: 271777486308 > >Keep the time, > >Gordon WA4FJC Probably the units in stock with the old brandname are going to be sold for less? Antonio I8IOV ___ 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] AVAR <-> S_Y conversion
Servus! On Thu, 05 Mar 2015 14:35:51 +0100 Wolfgang Wallner wrote: > For the random walk noise the expected line is off by a factor of > exactly 2 from the calculated plot, and I don't know how to explain this > behavior. I'm probably the wrong one to answer, as I have never done any noise simulation or even read up the relevant papers, but... A factor of 2 sounds like the difference you would get between one sided and two sided noise PSD's. Attila Kinali -- < _av500_> phd is easy < _av500_> getting dsl is hard ___ 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] new tdc from Texas
On Thu, 05 Mar 2015 09:39:44 -0500 Ben Gamari wrote: > Is this just a function of the ring oscillator > duty cycle being much smaller? There has been some development on how to do ring oscillators for TDC applications in recent years. Driven to a large part by the need for better (longer measure time, higher resolution, better linearity) TDCs for all digital PLLs (ADPLL). I haven't read it completely yet, but Straayers dissertation [1] gives a nice overview of a couple of methods on how to enhance ring oscillators for the use as a TDC. I also find [2] quite nice. They use delay lines to both store pulses and to stretch them. This enables them to work similar to a pipeline ADC. (I haven't read the paper completely either, so i might have misunderstood some stuff) Attila Kinali [1] "Noise Shaping Techniques for Analog and Time to Digital Converters Using Voltage Controlled Oscillators", by Straayer, 2008 http://cppsim.org/Publications/Theses/straayer_phdthesis.pdf [2] "A 9 bit, 1.12ps Resolution 2.5b/Stage Pipelined Time-to-Digital Converter in 65nm CMOS using Time-Register", by Kim, Yu, Cho, 2014 -- < _av500_> phd is easy < _av500_> getting dsl is hard ___ 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] 50 ohm driver
Hello, Thanks for all the feedback. I should explain. I have an existing product that uses the 74AC14. I have a customer who needs 5V into 50 ohm and can’t wait for the competitive product that does this, or for me to re-design my unit. So I have been looking for a quick fix. I got excited when I found the SN74AS1004AD which has the exact same function and pin out but delivers 48 mA per channel. While one output did give me 0-3.0 V into 50 ohm, combining them, as we do for the 74AC, actually produced worse results. Maybe the output driver is different. Anyway I’ve managed to get 0-4.8V by jacking up the supply voltage to 5.7 V for the 74AC14 and making the three 47 ohm resistors 0 ohm. Risetime < 4 ns. Basically to ideas that TimeNuts gave me. I’m just worried the IC may die after a few months. But since the customer will only use it at 1 Hz and hopefully 50:50 duty, or less, I hope to get away with it. Of course if he removes the input and the outputs are on high, then that may be a problem. BTW, the reason he wants this high voltage is because he is driving a very long cable from the distribution amp to the actual receiver. Anyway I have an IC on test for a week to make sure it lasts. Regards Martyn Today's Topics: 1. Re: 50 ohm Driver (Bob Albert) 2. Re: 50 ohm Driver (Graham / KE9H) 3. Re: 50 ohm Driver (Tom Van Baak) 4. Re: 50 ohm Driver (Hal Murray) 5. Re: 50 ohm Driver (Dan Kemppainen) 6. Re: Trimble Thunderbolt NMEA ? (Didier Juges) 7. Re: 50 ohm Driver (Bob Camp) 8. Re: 50 ohm Driver (Charles Steinmetz) 9. Re: new tdc from Texas (Angus) 10. Re: new tdc from Texas (Attila Kinali) -- Message: 1 Date: Wed, 4 Mar 2015 16:49:11 + (UTC) From: Bob Albert To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 50 ohm Driver Message-ID: <1276775018.2671439.1425487751520.javamail.ya...@mail.yahoo.com> Content-Type: text/plain; charset=UTF-8 5V into 50 Ohms means 100 mA. Perhaps you need a medium power transistor amplifier or opamp. Bob On Wednesday, March 4, 2015 6:09 AM, Martyn Smith wrote: Hello, A quick question. My output driver for a simple amplifier. I use three gates (in parallel with resistors) from a 74AC14 to give me about 0-3.2V into 50 ohm. I want to have a driver that gives me a full 0-5V (at least 0-4.5V) swing into 50 ohms. Can anyone recommend an IC that can delivery this. But it needs to have similar jitter performance to the 74AC14. I use it up to 10 MHz. Best Regards Martyn ___ 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. -- Message: 2 Date: Wed, 4 Mar 2015 12:16:02 -0600 From: "Graham / KE9H" To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 50 ohm Driver Message-ID: Content-Type: text/plain; charset=UTF-8 Building on top of John's comments, if you are using a logic gate, look at the maximum output (pull up) current per pin, set the series resistor so that this current is not exceeded into a short, then also see if there is a maximum total current draw for all gates combined, or some power input pin, and do not exceed that. You can also look at switching the termination resistor from a simple 50 Ohm resistor to ground, to a "Thevenin" load, which is 100 Ohms from +V to the load point, and another 100 Ohm resistor from the load point to ground. This way you still have a 50 Ohm termination, but only draw one half the DC current. In the event of no input, the receiver voltage will go to half scale. Make sure your system will not misbehave when this happens. Alternate driver is to use a video line driver with sufficient bandwidth. --- Graham / KE9H == On Wed, Mar 4, 2015 at 7:54 AM, John Ackermann N8UR wrote: > One comment on the parallel AC gate approach. It may not be directly > applicable to Martyn's issue, but there is a common confusion about the > value of the summing resistors. > > Per Tom Clark, who came up with the idea, they are *not* intended to > provide a near-end line termination to 50 ohms, but are simply there to > protect the paralleled devices if the gates have slightly different delays > (in which case one gate could end up sinking the other two). > > So, the commonly used 47 ohm value isn't magic. You can use a lower > value, and thus get more voltage at the far end. I haven't experimented to > see how far you can take that idea before destroying gates. > > John > > > On 3/4/2015 5:26 AM, Martyn Smith wrote: > >> Hello, >> >> A quick question. >> >> My output driver for a simple amplifier. >> >> I use three gates (in parallel with resistors) from a 74AC14 to give me >> about 0-3.2V into 50 ohm. >> >> I want to have a driver that gives me a full 0-5V (at
Re: [time-nuts] 50 ohm driver
mar...@ptsyst.com said: > BTW, the reason he wants this high voltage is because he is driving a very > long cable from the distribution amp to the actual receiver. If you have a long cable, the rise time at the driver isn't critical. It will get filtered out by the cable. Of course, how long is long? Here are some scope pictures for 100 ft of coax. The driver is a TBolt. I forget what chip they use. http://www.megapathdsl.net/~hmurray/time-nuts/coax/Coax-20ns.png If you are going to redesign the board and prefer chips to transistors, check out the bus driver chips. They typically come 8 drivers to a package. There used to be some with 16. There were also some chips that included a 25 ohm resister. They were intended for driving memory busses. -- 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] 50 ohm driver
Martyn, How long is the cable you are driving? If you have large ground differentials you may destroy the chips very easily. Especially if between industrial buildings. Some of the things discussed here are fine for a hobby environment but somewhat questionable in a commercial business. Regards Paul WB8TSL On Thu, Mar 5, 2015 at 4:59 PM, Martyn Smith wrote: > Hello, > Thanks for all the feedback. > I should explain. I have an existing product that uses the 74AC14. > I have a customer who needs 5V into 50 ohm and can’t wait for the > competitive product that does this, or for me to re-design my unit. > So I have been looking for a quick fix. > I got excited when I found the SN74AS1004AD which has the exact same > function and pin out but delivers 48 mA per channel. > While one output did give me 0-3.0 V into 50 ohm, combining them, as we do > for the 74AC, actually produced worse results. > Maybe the output driver is different. > Anyway I’ve managed to get 0-4.8V by jacking up the supply voltage to 5.7 > V for the 74AC14 and making the three 47 ohm resistors 0 ohm. > Risetime < 4 ns. > Basically to ideas that TimeNuts gave me. > I’m just worried the IC may die after a few months. But since the > customer will only use it at 1 Hz and hopefully 50:50 duty, or less, I hope > to get away with it. > Of course if he removes the input and the outputs are on high, then that > may be a problem. > BTW, the reason he wants this high voltage is because he is driving a very > long cable from the distribution amp to the actual receiver. > Anyway I have an IC on test for a week to make sure it lasts. > Regards > Martyn > > > Today's Topics: > >1. Re: 50 ohm Driver (Bob Albert) >2. Re: 50 ohm Driver (Graham / KE9H) >3. Re: 50 ohm Driver (Tom Van Baak) >4. Re: 50 ohm Driver (Hal Murray) >5. Re: 50 ohm Driver (Dan Kemppainen) >6. Re: Trimble Thunderbolt NMEA ? (Didier Juges) >7. Re: 50 ohm Driver (Bob Camp) >8. Re: 50 ohm Driver (Charles Steinmetz) >9. Re: new tdc from Texas (Angus) > 10. Re: new tdc from Texas (Attila Kinali) > > > -- > > Message: 1 > Date: Wed, 4 Mar 2015 16:49:11 + (UTC) > From: Bob Albert > To: Discussion of precise time and frequency measurement > > Subject: Re: [time-nuts] 50 ohm Driver > Message-ID: > <1276775018.2671439.1425487751520.javamail.ya...@mail.yahoo.com> > Content-Type: text/plain; charset=UTF-8 > > 5V into 50 Ohms means 100 mA. Perhaps you need a medium power transistor > amplifier or opamp. > Bob > > > On Wednesday, March 4, 2015 6:09 AM, Martyn Smith > wrote: > > > Hello, > > A quick question. > > My output driver for a simple amplifier. > > I use three gates (in parallel with resistors) from a 74AC14 to give me > about 0-3.2V into 50 ohm. > > I want to have a driver that gives me a full 0-5V (at least 0-4.5V) swing > into 50 ohms. > > Can anyone recommend an IC that can delivery this. > > But it needs to have similar jitter performance to the 74AC14. > > I use it up to 10 MHz. > > Best Regards > > Martyn > > ___ > 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. > > > > > -- > > Message: 2 > Date: Wed, 4 Mar 2015 12:16:02 -0600 > From: "Graham / KE9H" > To: Discussion of precise time and frequency measurement > > Subject: Re: [time-nuts] 50 ohm Driver > Message-ID: > > Content-Type: text/plain; charset=UTF-8 > > Building on top of John's comments, if you are using a logic gate, look at > the > maximum output (pull up) current per pin, set the series resistor so that > this > current is not exceeded into a short, then also see if there is a maximum > total > current draw for all gates combined, or some power input pin, and do not > exceed > that. > > You can also look at switching the termination resistor from a simple 50 > Ohm > resistor to ground, to a "Thevenin" load, which is 100 Ohms from +V to the > load point, > and another 100 Ohm resistor from the load point to ground. This way you > still have a 50 Ohm termination, but only draw one half the DC current. > In the event of no input, the receiver voltage will go to half scale. Make > sure your system will not misbehave when this happens. > > Alternate driver is to use a video line driver with sufficient bandwidth. > > --- Graham / KE9H > > == > > On Wed, Mar 4, 2015 at 7:54 AM, John Ackermann N8UR wrote: > > > One comment on the parallel AC gate approach. It may not be directly > > applicable to Martyn's issue, but there is a common confusion about the > > value of the summing resistors. > > > > Per Tom Clark, who came up with the idea, they are *not* intended to > > provide a near-end line termination to 50 ohms, but are simply there to > > protect the paralleled devices if the gates have slightly different > delays >
