Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On 6/11/2017 6:09 AM, Magnus Danielson wrote: Hi, What papers would you recommend reading? One of the things that we experimented on and improved was the passive wall to prohibit quick cooling of oven. A puff of air or the forced convection (fans) needed for other electronics would tie the

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi A great starting point is Rick’s paper on the Hockey Puck. Bob > On Jun 11, 2017, at 9:09 AM, Magnus Danielson > wrote: > > Hi, > > What papers would you recommend reading? > > One of the things that we experimented on and improved was the passive wall > to

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi, What papers would you recommend reading? One of the things that we experimented on and improved was the passive wall to prohibit quick cooling of oven. A puff of air or the forced convection (fans) needed for other electronics would tie the metal shield very well to surrounding

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi One of the bigger unknowns in all this is how tight your control point needs to be held in order that your crystal only sees 0.1C. So far we have sort of assumed that the control point and the crystal see the same thing. That’s never the case. If the outside temperature goes from -30 to

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

albertson.ch...@gmail.com said: > I say "effective" because we can dither the low order bits to gain maybe 6 > effective bits form 4 real bits (we can filter the switching noise from a > low frequency dither) It's hard to filter low frequencies and the more bits you gain by dithering the lower

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi > On Jun 10, 2017, at 5:15 PM, Poul-Henning Kamp wrote: > > > In message , Bob kb8tq writes: > >> If you want the controller noise to *not* be the limiting factor at an ADEV >> floor of 1x10^-12, >> that drives

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

In message , Bob kb8tq writes: >If you want the controller noise to *not* be the limiting factor at an ADEV >floor of 1x10^-12, >that drives you to a noise floor of < 0.1 mK. You can then work through the >various thermal >gains to come

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi > On Jun 10, 2017, at 4:10 PM, Chris Albertson > wrote: > > On Sat, Jun 10, 2017 at 12:59 PM, Poul-Henning Kamp > wrote: > >> >> >> Delta-Sigma strategies for spreading the noise-spectrum are >> interesting, but will not save you

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

In message <73a71ef4-eb76-4965-b3d5-53f9dd5bf...@n1k.org>, Bob kb8tq writes: >If we want to hold the oven at some temperature +/- 0.1 C, the control loop >needs to go from full on to full off over that range. ...ehhh, what ? >You will map (somehow) the full range of the output into a

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi, As a side comment. I've seen an OCXO misbehave such that it was bang-bang regulating. For a short while it was heating up and then the crystal was cooling down slowly until the heater was turned on again, shortly. The effect being that the temperature of the crystal was essentially a

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi The next issue is that “noise” has a pretty broad definition in this case. If you are looking at set point, it also would include temperature drift and aging. Neither one seem to show up on the standard MCU ADC data sheets :) It can even be a bit difficult to find them on some (but certainly

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi, On 06/10/2017 09:59 PM, Poul-Henning Kamp wrote: In message <017ac7d5-751b-4084-a3b3-e5132509c...@n1k.org>, Bob kb8tq writes: You may well use a custom set of control parameters for the warmup phase. The easiest way to avoid overshoot is to use a properly damped PI(D), which is

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On Sat, Jun 10, 2017 at 12:59 PM, Poul-Henning Kamp wrote: > > > Delta-Sigma strategies for spreading the noise-spectrum are > interesting, but will not save you if the required heater power > ends up being a small rational fraction (1/2, 1/3, 1/4 ...) of the > full

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

In message <017ac7d5-751b-4084-a3b3-e5132509c...@n1k.org>, Bob kb8tq writes: >You may well use a custom set of control parameters for the warmup phase. The easiest way to avoid overshoot is to use a properly damped PI(D), which is _exactly_ the same thing you want once you are out of

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On Sat, Jun 10, 2017 at 11:33 AM, Magnus Danielson < mag...@rubidium.dyndns.org> wrote: > Hi, > > I was about to make this very point myself. The resolution of the ADC > needs to be higher than the limit you try to achieve. There is several ways > to reason about it, but one is that the system is

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi At least in my experience, a properly functioning OCXO will rarely (if ever) be outside +/- 1 degree of the set point when in full PID (integrator enabled) mode. You may well use a custom set of control parameters for the warmup phase. You might even use a non-PID based control (shut off

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi, Very good point Poul-Henning, very good point. The mux is there, we don't need the resolution far out, and with only a little though code-wise and hardware wise we get the best of resolution and range where we need it. Cheers, Magnus On 06/10/2017 09:06 PM, Poul-Henning Kamp wrote:

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

In message <3897c09a-d76c-474c-8907-9ea25f8c3...@n1k.org>, Bob kb8tq writes: >The “limited range” part of it is why the op-amp makes so much >sense. If the ADC can “see” +/-10C that’s way more than will ever be useful. Most uC's have a pile of mux'ed ADC inputs, so do all of the above:

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi, Indeed. I prefer to have margins and dynamics, as it makes it easier. Cutting in on that will require more work to ensure it works, hence you have to work more to save money in order to maintain stable operations. Cheers, Magnus On 06/10/2017 08:50 PM, Bob kb8tq wrote: Hi The “limited

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi The “limited range” part of it is why the op-amp makes so much sense. If the ADC can “see” +/-10C that’s way more than will ever be useful. You could make a pretty good case for -5/ +1 C as being way more than you will ever use. The only real issue with the +1 is ok argument is when you

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi, I was about to make this very point myself. The resolution of the ADC needs to be higher than the limit you try to achieve. There is several ways to reason about it, but one is that the system is a bit slugish you want to have higher resolution in order to react of changes before they

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi > On Jun 8, 2017, at 3:41 AM, Hal Murray wrote: > > > att...@kinali.ch said: >> Keep in mind that you will need a good voltage reference as well to reach >> anything close to 12bit. Your LDO is _not_ a good voltage reference >> (depending on type and load/source

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

att...@kinali.ch said: > Keep in mind that you will need a good voltage reference as well to reach > anything close to 12bit. Your LDO is _not_ a good voltage reference > (depending on type and load/source conditions they vary eaily by 1-2%... not > to talk about their noise) That applies when

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi Folks, This discussion of temperature measurement with ADCs has crossed into my professional life and without being too much of a commercial plug just wanted to mention that I support Linear Technology's temp-to-bits family of ICs: LTC2983, LTC2984, LTC2986. Overview: each part has 3

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On 6/7/17 7:35 PM, Bob kb8tq wrote: Hi Metal actually makes things a bit worse since it has a lower thermal resistance than glass. This is also why a high performance dewar is made from glass rather than metal. Yes, you can go to weird stuff like titanium (it has been done). You can’t afford

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi Metal actually makes things a bit worse since it has a lower thermal resistance than glass. This is also why a high performance dewar is made from glass rather than metal. Yes, you can go to weird stuff like titanium (it has been done). You can’t afford that …. If you fill the entire

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

For under $20 you can get a OCXO with Si5351A multi output oscillator chip from QRP-Labs. http://www.qrp-labs.com/ocxokit.html No idea just how good it is but this link gives insight into how it was developed. Designed for WSPR radio transmissions. GPS discipline can be added.

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi Consider that a lot of the heat flow is through the glass wall of the vacuum gizmo. You want to tie your heater(s) to it in order to create an iso-thermal “wall”. Often this is done by gluing the whole assembly together. In addition, you probably also want a foam plug in the end of the

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On Wed, 7 Jun 2017 22:20:50 +0100 Peter Vince wrote: > > Additionally: if I would set out to build my own OCXO today, I would > > go and buy one of those lunch thermos flasks to house everything. Their > > isolation is higher than anything you can easily build yourself,

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Chris wrote: Assume me goal is to regulate temperer of an aluminum block to within 0.1C, how good must my ADC be? Is an effective 6-bits good enough? * * *If I scale the input to the ADC such that it os 1.0C from 0 to 63 counts then each cunt is 1/64 C which is about 6 times better

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi > On Jun 7, 2017, at 4:40 PM, Attila Kinali wrote: > > On Wed, 7 Jun 2017 15:25:38 -0400 > Charles Steinmetz wrote: > >> Chris wrote: >> >>> Assume me goal is to regulate temperer of an aluminum block to within >>> 0.1C, how good must my ADC be?

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On 7 June 2017 at 21:40, Attila Kinali wrote: > > Additionally: if I would set out to build my own OCXO today, I would > go and buy one of those lunch thermos flasks to house everything. Their > isolation is higher than anything you can easily build yourself, > especially at

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On Wed, 7 Jun 2017 15:25:38 -0400 Charles Steinmetz wrote: > Chris wrote: > > > Assume me goal is to regulate temperer of an aluminum block to within > > 0.1C, how good must my ADC be? Is an effective 6-bits good enough? > > > > * * *If I scale the input to the

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On Tue, 6 Jun 2017 16:43:30 -0700 Chris Albertson wrote: > > . Heck, the STM32F4xx have so much internal noise that the ENOB > > of their ADC is below 6bit... so low that they even had to write an > > appnote on how to do averaging to get back to the 12 bits the ADC is

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

albertson.ch...@gmail.com said: > Assume me goal is to regulate temperer of an aluminum block to within 0.1C, > how good must my ADC be? Is an effective 6-bits good enough? I don't think you are asking the right question. You can build a control loop with a 1 bit ADC. Think of your typical

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

The good news is that for oven control, you can typically filter the heck out of the data and the noise may actually help you with dithering if it's fairly random, so you should be able to get close to the specs. The main thing you need is stability, linearity should not be a factor. One

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi There is a gotcha with the initial assumption: You want the loop to be *quiet* at a level well below 0.1C. If it is bouncing around that much, the second order (rate defendant) tempco of a normal crystal will become a pretty major issue. Simple rule of thumb - add at least two bits past

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

One question for the control theory experts. Assume me goal is to regulate temperer of an aluminum block to within 0.1C, how good must my ADC be? Is an effective 6-bits good enough? It seems to me the problem with fewer bits is only quantization noise. Lets assume 6-bits. This is 1 part in

[time-nuts] uC ADC resolution (was: Poor man's oven)

Another thing to watch out for on processor ADCs is their performance near the supply rails... the AVR ADCs are particularly entertaining below around 300 mV (with a 5V Vref). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

Hi You can only get back bits to the degree that the problems are caused by noise. If it is 1/F noise, averaging over long periods is going to be really tough. Bob > On Jun 6, 2017, at 7:43 PM, Chris Albertson wrote: > > On Tue, Jun 6, 2017 at 2:17 PM, Attila

Re: [time-nuts] uC ADC resolution (was: Poor man's oven)

On Tue, Jun 6, 2017 at 2:17 PM, Attila Kinali wrote: > On Tue, 6 Jun 2017 16:37:27 -0400 > Bob kb8tq wrote: > > . Heck, the STM32F4xx have so much internal noise that the ENOB > of their ADC is below 6bit... so low that they even had to write an > appnote on

[time-nuts] uC ADC resolution (was: Poor man's oven)

On Tue, 6 Jun 2017 16:37:27 -0400 Bob kb8tq wrote: > 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