Re: [time-nuts] Poor man's oven

Hi > On Jun 8, 2017, at 2:18 AM, Hal Murray wrote: > > > kb...@n1k.org said: >> The crystal enclosure may (or may not … who knows ..) be back filled with a >> low level of helium. It does not take much of a backfill for conduction >> inside the crystal holder to

Re: [time-nuts] Poor man's oven

kb...@n1k.org said: > The crystal enclosure may (or may not … who knows ..) be back filled with a > low level of helium. It does not take much of a backfill for conduction > inside the crystal holder to dominate the heat transfer vs radiation > transfer. How does that compare with conduction

Re: [time-nuts] Poor man's oven

Hi Keep in mind that on a per cubic inch basis, copper is right up there for creating a thermal mass …. Bob > On Jun 7, 2017, at 5:51 PM, Attila Kinali wrote: > > Hoi Rick, > > On Wed, 7 Jun 2017 14:21:52 -0700 > "Richard (Rick) Karlquist" wrote: > >

Re: [time-nuts] Poor man's oven

Hoi Rick, On Wed, 7 Jun 2017 14:21:52 -0700 "Richard (Rick) Karlquist" wrote: > Actually, the oven mass of the E1938A is much heavier than the > 10811 and is made of copper to boot. [...] > The crystal case is well connected to the oven mass and gets > heated by

Re: [time-nuts] Poor man's oven

Hi The crystal enclosure may (or may not … who knows ..) be back filled with a low level of helium. It does not take much of a backfill for conduction inside the crystal holder to dominate the heat transfer vs radiation transfer. Bob > On Jun 7, 2017, at 5:21 PM, Richard (Rick) Karlquist

Re: [time-nuts] Poor man's oven

On 6/7/2017 1:09 PM, Attila Kinali wrote: makes the PI loop better behaved. Also the thermal mass of the crystal holder is quite small. Especially compared ot the 10811. Actually, the oven mass of the E1938A is much heavier than the 10811 and is made of copper to boot. Due to the flat

Re: [time-nuts] Poor man's oven

On Tue, 6 Jun 2017 19:07:29 -0700 "Richard (Rick) Karlquist" wrote: > In the E1938A oscillator, we used a PIDI^2 loop. IOW, a PID > plus a double integrator. This was Len Cutler's idea. > Once the constants were dialed in, this worked phenomenally > well in terms of

Re: [time-nuts] Poor man's oven

is important, and yet the circuit isn't capable of that much accuracy. -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Harman Sent: Tuesday, June 6, 2017 11:09 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts

Re: [time-nuts] Poor man's oven

On Jun 6, 2017, at 7:10 PM, Chris Albertson wrote: There are more sophisticated control loop designs that can handle this better, eg by using two temperature sensors, one at the crystal and one at the heater. But designing them correctly is more difficult than

Re: [time-nuts] Poor man's oven

Hi The Freescale ADC’s are pretty good compared to a lot of other MCU ADC’s. They still are not as good as you might think from the audio ENOB numbers. Something in the 10~11 bit range is doing quite well at DC in a control loop, even for them. Bob > On Jun 6, 2017, at 8:12 PM, jimlux

Re: [time-nuts] Poor man's oven

On 6/6/17 1:37 PM, Bob kb8tq wrote: Hi Often when you dig into the details of MCU ADC’s they have a little note “optimized for audio” or “not recommended for control loops”. It can be a bit of a head scratcher to work out what they are getting at. The big issues in this case seem to be DC

Re: [time-nuts] Poor man's oven

Hi In the case of a second sensor, “at the crystal” effectively means “inside the crystal package”. That heads you into all sorts of “interesting” problems. Better to just read the papers and do it the “old fashioned” way. Bob > On Jun 6, 2017, at 7:10 PM, Chris Albertson

Re: [time-nuts] Poor man's oven

> There are more sophisticated control loop designs that can handle this > better, eg by using two temperature sensors, one at the crystal and > one at the heater. But designing them correctly is more difficult > than the normal PID loop. > Keeping with the thread topic, I think this is the key.

Re: [time-nuts] Poor man's oven

On Tue, 6 Jun 2017 11:00:57 -0700 Chris Albertson wrote: > > > > 1) You want the control loop as stable as possible > > 2) Stability is directly related to controllability > > 3) The larger the heat flow, the better the controllability > > 4) therefore the outside

Re: [time-nuts] Poor man's oven

Hi Often when you dig into the details of MCU ADC’s they have a little note “optimized for audio” or “not recommended for control loops”. It can be a bit of a head scratcher to work out what they are getting at. The big issues in this case seem to be DC leakage and 1/F noise. Yes, they do

Re: [time-nuts] Poor man's oven

On 6/6/17 11:47 AM, Chris Albertson wrote: Yes, as I wrote. I would not mess with AREF. At most you can only get a multiplication about 4. Use an op-amp. Signal conditioning really almost alway is required in the analog domain before any A/D conversion Also like the uP is not inside the

Re: [time-nuts] Poor man's oven

In message , Chris Albertson writes: >The next step up the complexity scale would have you place an I2C >interlaced ADC inside your oven. These don't cost much and have several >ADC channels. ISOtemp made a version of

Re: [time-nuts] Poor man's oven

csteinm...@yandex.com said: > It depends on what you mean by "best." "Best" can mean "minimizes the > wander in oven-regulated temperature at a constant (or slowly-changing) > ambient temperature," or it can mean "fastest recovery when the ambient > temperature changes more rapidly." I think

Re: [time-nuts] Poor man's oven

Yes, as I wrote. I would not mess with AREF. At most you can only get a multiplication about 4. Use an op-amp. Signal conditioning really almost alway is required in the analog domain before any A/D conversion Also like the uP is not inside the oven and has a cable of some length so you'd

Re: [time-nuts] Poor man's oven

Hi As you point out, there really is no answer that is obviously better than all the others. If you keep the outside warm (say 40C) you will reduce the strain on the heater devices and likely not degrade the MTBF of anything outside the OCXO by very much. Bob > On Jun 6, 2017, at 7:26 AM,

Re: [time-nuts] Poor man's oven

On 6/6/2017 4:26 AM, Poul-Henning Kamp wrote: But I cant imagine the ovens used are so perfect that they have the same regulation performance at all temperatures. I can choose the exterior temperature, which I should prefer ? Disregard aging of electronics and materials, we all know that

Re: [time-nuts] Poor man's oven

Hi For a variety of reasons, if you go the MCU ADC route, put an op amp in between the thermistor bridge and the ADC. It takes care of a whole lot of issues. Bob > On Jun 6, 2017, at 12:13 PM, Adrian Godwin wrote: > > The specs for the ADC are pretty vague : most of the

Re: [time-nuts] Poor man's oven

Poul-Henning wrote: what I'm interested in is at which exterior temperature OCXO ovens work best ? Jim replied: Here's my guess... 1) you want minimal gradients across the device for a variety of reasons 2) therefore you want least amount of heat from the heater 3) therefore somewhat below

Re: [time-nuts] Poor man's oven

On Tue, Jun 6, 2017 at 7:34 AM, Attila Kinali wrote: > > 1) You want the control loop as stable as possible > 2) Stability is directly related to controllability > 3) The larger the heat flow, the better the controllability > 4) therefore the outside temperature should be as

Re: [time-nuts] Poor man's oven

On Tue, Jun 6, 2017 at 10:00 AM, Riley, Ian C CTR NSWC Philadelphia, 515 < ian.riley@navy.mil> wrote: > Is there a practical minimum for what voltage you can feed into AREF? > It is hard to find on the data sheet, but the minimum voltage for an Arduino's AREF is the internal analog reference

Re: [time-nuts] Poor man's oven

The specs for the ADC are pretty vague : most of the errors are around 2 LSB but all are quoted with vref at 4V. If you reduce vref (there's an internal option of 1.1V) you'll increase gain but some of those errors are going to stay physically the same. In general, I'd tend expect to get more

Re: [time-nuts] Poor man's oven

Chris, > The trick with using a uP and it's built-in A/D converters is scale. You > want the limited 10-bits of revolution to fall over the operating range > which is very narrow, like 1C. Anything outside of that is either or > and only seen at start-up., So at start up the the

Re: [time-nuts] Poor man's oven

On Tue, 6 Jun 2017 05:52:56 -0700 jimlux wrote: > > Disregard aging of electronics and materials, we all know that > > stuff, what I'm interested in is at which exterior temperature > > OCXO ovens work best ? > > Here's my guess... > > 1) you want minimal gradients across

Re: [time-nuts] Poor man's oven

On 6/6/17 4:26 AM, Poul-Henning Kamp wrote: OCXO's have specified temperature ranges for instance -40...+70°C for the heavy duty stuff. But I cant imagine the ovens used are so perfect that they have the same regulation performance at all temperatures. I can choose the exterior

Re: [time-nuts] Poor man's oven

In message , Bob kb8tq writes: >In an OCXO design, the gotcha >is matching the PTC oven temperature to the crystal turn. You can do that if >you have a substantial inventory of material and custom fab the oven after >the crystal is built.

Re: [time-nuts] Poor man's oven

Hi For a while, a couple of outfits made TO-5 and TO-8 “cap heaters” with PTC material. There are still a few obscure places that people do the same sort of thing with a mini-pcb based design. In an OCXO design, the gotcha is matching the PTC oven temperature to the crystal turn. You can do that

Re: [time-nuts] Poor man's oven

Folks, with tongue firmly stuck in cheek, may I propose an old technique to stabilize xtal oscillators?You only need a "satellite" oscillator placed under your armpit... http://www.qsl.net/on7yd/136narro.htm#NihilNovum jon, ea2sn ___ time-nuts mailing

Re: [time-nuts] Poor man's oven

I have never been able to find a reference to them on the internet but there was a similar product intended for TO-99 packages that could be used with operational amplifiers. On Mon, 5 Jun 2017 08:35:35 + (UTC), you wrote: >  The Crystal heater clip wasa Murata "Posistor" soldered onto a

Re: [time-nuts] Poor man's oven

Chris wrote: Today all you need is a reliable way to measure the error between the crystals' current temperature and the set point. That's all that's ever been needed. But it is devilishly difficult to measure the actual quartz temperature, or even to find a good proxy that is easier to

Re: [time-nuts] Poor man's oven

Hi That paper is the basis for the MCXO. It is an interesting way to do a TCXO. The drift between the two modes makes it a difficult thing to master in an OCXO. Plating a pair of electrodes (one pair per mode) is also an approach that has been tried. Bob > On Jun 5, 2017, at 7:20 PM, Chris

Re: [time-nuts] Poor man's oven

Hi For further info on just why the crystal temperature is such a crazy thing to track, check out Rick’s paper. At first glance it *seems* like it’s a trivial thing. In reality, gradients are a very big deal. Bob > On Jun 5, 2017, at 6:38 PM, Charles Steinmetz wrote: >

Re: [time-nuts] Poor man's oven

On Mon, June 5, 2017 5:38 pm, Charles Steinmetz wrote: > Some years ago, I consulted for a research group that was using a number > of non-contact technologies to measure the temperature of oscillating > quartz crystals. In most cases what you really care about is the stability of the frequency,

Re: [time-nuts] Poor man's oven

On Mon, Jun 5, 2017 at 3:38 PM, Charles Steinmetz wrote: > Chris wrote: > > Today all you need is a reliable way to measure the error >> between the crystals' current temperature and the set point. >> > > That's all that's ever been needed. But it is devilishly difficult

Re: [time-nuts] Poor man's oven

Look at the dates on the uses of these exotic temperature controllers. Organic compounds and positive temp coefficients and so on. All these were used before the current era. Today all you need is a reliable way to measure the error between the crystals' current temperature and the set point.

Re: [time-nuts] poor-man's oven

Yes, Agree. I wrote tin the first post that "for your use a resistive heater would be better" But everything else, I'd do over. Drill the aluminum block and use thermal epoxy to hold the sensor in place. Use a vacuum insulated mug or bowl for a cover and let a micro controller run a PID loop

Re: [time-nuts] Poor man's oven

Wax is also used for thermostatic valves in engine cooling systems and domestic heating systems. On Mon, Jun 5, 2017 at 1:13 PM, Tim Shoppa wrote: > Here is a national new-technology of the art crystal oven from 1956: > > http://tf.boulder.nist.gov/general/pdf/1642.pdf > >

Re: [time-nuts] poor-man's oven

On 6/4/17 10:01 PM, Chris Albertson wrote: Voltage is proportional to the product of resistance and absolute temperature. As an experiment place a voltage across a high value resister like say one 1M raise the volts until you are near the limit of the resister and connect it via a coupler

Re: [time-nuts] Poor man's oven

Here is a national new-technology of the art crystal oven from 1956: http://tf.boulder.nist.gov/general/pdf/1642.pdf Using the phase change properties of p-dibromobenzene it keeps temperature constant to 0.01C. It notes other organic compounds can be used for different temperature ranges.

Re: [time-nuts] Poor man's oven

Hi The posistor approach to heating a crystal was originally pioneered in Russia. Morion was building vacuum insulated / PTC controlled OCXO’s long before the PTC parts started showing up more generally in the 1970’s. Bob > On Jun 5, 2017, at 4:35 AM, Ulf Kylenfall via time-nuts

Re: [time-nuts] Poor man's oven

There's a few 'OCXO' designs out there, I'm not qualified to comment on the timenutty quality of them but someone else mentioned Hans Summers offerings and I would offer Roman Black's simple design (if it's not been mentioned already): http://www.romanblack.com/xoven.htm I've no idea if it's

Re: [time-nuts] poor-man's oven

On Sun, 4 Jun 2017 22:01:45 -0700 Chris Albertson wrote: > Voltage is proportional to the product of resistance and absolute > temperature. As an experiment place a voltage across a high value > resister like say one 1M raise the volts until you are near the limit

Re: [time-nuts] Poor man's oven

Not quite as simple as the PTC, an alternative may be: http://shop.kuhne-electronic.de/kuhne/en/shop/accessoires/crystal-heater/Precision+crystal+heater+40%C2%B0+QH40A/?card=724 No it probably doesn't hold the crystal at it's optimum turn over temperature, but it will keep the temperature of a

Re: [time-nuts] poor-man's oven

Voltage is proportional to the product of resistance and absolute temperature. As an experiment place a voltage across a high value resister like say one 1M raise the volts until you are near the limit of the resister and connect it via a coupler cadaster to an audio amplifier. You will hear

Re: [time-nuts] poor-man's oven

Yes, I have a TEC mounted on a convection heatsink that illustrates that point. Initially ice forms on the cold surface but eventually the heatsink temperature rises sufficiently that the ice melts. A larger blown heatsink or perhaps a water cooled heatsink would be necessary if this setup was

Re: [time-nuts] poor-man's oven

Hi Many times people underestimate the amount of heat sinking required with a TEC. If you get into fans, they introduce a whole new set of issues ….It’s not just the heat you are getting out of the “oven”. The TEC it’s self makes a pretty good thermal short (compared to foam insulation). You

Re: [time-nuts] poor-man's oven

Really?? The circuitry employed is something of a joke surely? Relying on the MOSFET characteristics to limit warm up current is unwise. The temperature sensor also would appear to suffer from large variations in output from one part to another. Bruce > > On 05 June 2017 at 01:21 "R.

Re: [time-nuts] poor-man's oven

My concern with using a TEC is that, heating or cooling, you are left with one cold surface and that surface will collect condensation which is a source for corrosion. John WA4WDL > On June 4, 2017 at 8:12 PM Attila Kinali wrote: > > > Moin Chris, > > On Sun, 4 Jun 2017

Re: [time-nuts] poor-man's oven

Moin Chris, On Sun, 4 Jun 2017 13:49:29 -0700 Chris Albertson wrote: > We used the pelter because we preferred a cool "oven" to a hot one. The > theory has that we get less electronic noise so we ran the TEC in cooling > mode. But for your use a resistive heater

Re: [time-nuts] poor-man's oven

Look at the temperature coefficient of your XO. Then figure a very simply control loop and a thermistor will keep a block of aluminum within 0.1C of a set point. Use a decent size block and insulation We drilled a deep hole then epoxied the thermistor. I think this step is important as you

Re: [time-nuts] poor-man's oven

Maybe you want to check out the work of Hans Summers he has done some impressive low cost stuff: http://www.hanssummers.com/ocxosynth.html http://www.qrp-labs.com/ocxokit.html Ralph On Sun, Jun 4, 2017 at 07:19 jimlux wrote: > I recall some years ago folks were talking

Re: [time-nuts] poor-man's oven

Hi If you have not done so already, you might try bumping the temperature a bit to search for the upper turn in the crystal curve. Based on the data in the plots, you do have an AT that is cut with an upper turn. Bob > On Jun 4, 2017, at 11:30 AM, Dan Rae wrote: > >

Re: [time-nuts] poor-man's oven

The attached plot shows the sort of improvement in warm up time and stability of a simple "oven" made by attaching a Darlington heater transistor and thermistor to a Crystek 100 MHz oscillator, adjusted to set the osc temp to around 35C and wrapping it all in foam. In this application, a DDS

Re: [time-nuts] poor-man's oven

Hi There is no way to know how every outfit makes their products. My guess is that the temperature compensation “stuff” is pretty stable. At least it has been on all the product I’ve designed :) I’d bet that the crystals in the TCXO’s are the culprit. In some of the factories I’ve visited,

Re: [time-nuts] poor-man's oven

Bob, at the same time, look at all the guys here who absolutely insist that the only way to use a double-oven OCXO is to put it in a tightly temperature controlled environment. "Nuts", yes, but that's why we're here! I myself have been extremely disappointed with the aging characteristics of

Re: [time-nuts] poor-man's oven

Hi The gotcha is that you have multiple systems working against each other. The crystal in the TCXO has one temperature characteristic. The compensation in the TCXO has a temperature characteristic. They cancel each other out to a limited degree. The residual slope may (or may not) be as

Re: [time-nuts] poor-man's oven

My SDR-1000 showed substantially less "WWV drift" after adding the PTC thermistor to the TCXO. Sorry, no measurements because that was before I had a GPSDO. Mikr - AA8K On 06/04/2017 08:13 AM, jimlux wrote: I recall some years ago folks were talking about putting a PTC thermistor on the

Re: [time-nuts] poor-man's oven

We did this years ago on a 430 MHz data radio with an utterly uncompensated crystal that would drift through the passband.  After building our own for a while, we discovered that Yaesu had something even better available through their replacement parts shop -- a spring clip with PTC that