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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Instead scopes
Date: Sun, 1 Sep 2024 15:15:39 +1000
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On 1/09/2024 4:57 am, john larkin wrote:
> On Sun, 1 Sep 2024 01:43:32 +1000, Bill Sloman <bill.sloman@ieee.org>
> wrote:
> 
>> On 1/09/2024 12:03 am, john larkin wrote:
>>> On Sat, 31 Aug 2024 16:03:39 +1000, Bill Sloman <bill.sloman@ieee.org>
>>> wrote:
>>>
>>>> On 31/08/2024 3:14 am, john larkin wrote:
>>>>> On Fri, 30 Aug 2024 14:17:14 +1000, Bill Sloman <bill.sloman@ieee.org>
>>>>> wrote:
>>>>>
>>>>>> On 30/08/2024 4:59 am, john larkin wrote:
>>>>>>> On Thu, 29 Aug 2024 20:23:19 +1000, Bill Sloman <bill.sloman@ieee.org>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> On 29/08/2024 2:32 am, john larkin wrote:
>>>>>>>>> On Wed, 28 Aug 2024 15:21:00 -0000 (UTC), Sergey Kubushyn
>>>>>>>>> <ksi@koi8.net> wrote:
>>>>>>>>>
>>>>>>>>>> john larkin <jlarkin_highland_tech> wrote:
>>>>>>>>>>> On Wed, 28 Aug 2024 04:28:02 -0000 (UTC), Sergey Kubushyn
>>>>>>>>>>> <ksi@koi8.net> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> john larkin <jlarkin_highland_tech> wrote:
>>>>>>>>>>>>> On Tue, 27 Aug 2024 14:55:32 -0400 (EDT), Martin Rid
>>>>>>>>>>>>> <martin_riddle@verison.net> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> john larkin <jlarkin_highland_tech> Wrote in message:r
>>>>>>>>>>>>>>> On Tue, 27 Aug 2024 10:40:15 -0400 (EDT), Martin Rid<martin_riddle@verison.net> wrote:>Anyone own the gds-1202b ?>>Any good?>>$350 at tequipment>>CheersI haven't tried that one. We like the Rigols.I recently acquired a Siglenthttps://www.amazon.com/gp/product/B06XZML6RD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1and gave it to one of my engineers. I'll ask him how he likes it.It has an up-front DEFAULT button, which a digital scope needs to getyou out of nightmare states.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Other than the lack of software features,  the 200mhz bw for 350
>>>>>>>>>>>>>> dollars is intriguing.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Cheers
>>>>>>>>>>>>>
>>>>>>>>>>>>> It sounds pretty good to me.
>>>>>>>>>>>>>
>>>>>>>>>>>>> https://siglentna.com/wp-content/uploads/dlm_uploads/2020/02/SDS1000X-E_DataSheet_DS0101E-E04C.pdf
>>>>>>>>>>>>>
>>>>>>>>>>>>> What's missing?
>>>>>>>>>>>>>
>>>>>>>>>>>>> I like the 500 uV/div.
>>>>>>>>>>>>
>>>>>>>>>>>> If you want to save the last penny, maybe. But you can get way better scope
>>>>>>>>>>>> for slightly more -- Rigol DHO800/DHO900. It is 12-bit, same 550uV/div, has
>>>>>>>>>>>> all standard serial protocols decoding, very light and compact, can work
>>>>>>>>>>> >from a battery with USB-C power connector, way better than that Siglent that
>>>>>>>>>>>> feels like relic next to those DHOs.
>>>>>>>>>>>
>>>>>>>>>>> We use almost all Rigols at work. My slow bench scope is a 500 MHz
>>>>>>>>>>> DS4034 (upgraded from 350 MHz)
>>>>>>>>>>>
>>>>>>>>>>> https://www.dropbox.com/scl/fo/ns08x686afbayjsw8c2ab/h?rlkey=iu4h89057t755pueg4ijnldbo&dl=0
>>>>>>>>>>>
>>>>>>>>>>> and my fast scope is a Tek 11802 sampler.
>>>>>>>>>>
>>>>>>>>>> I also have one, 11801C. Couple of SD-24s, SD-20, and SD-22 heads :)
>>>>>>>>>
>>>>>>>>> At the original purchase price, adjusted for inflation, I must have
>>>>>>>>> half a million dollars worth of sampling heads.
>>>>>>>>>
>>>>>>>>> The color grading and jitter measurement is great on the 11801C, but
>>>>>>>>> the old B+W screens photograph better.
>>>>>>>>>
>>>>>>>>> I'll miss my 11802 when it eventually dies.
>>>>>>>>>
>>>>>>>>> The TDR is great. I'm going to give my new kids a lecture on
>>>>>>>>> transmission lines, and I'll show them some TDR.
>>>>>>>>>
>>>>>>>>> It is apparently possible these days to get an EE degree and be
>>>>>>>>> completely ignorant of transmission lines. Or even electricity.
>>>>>>>>
>>>>>>>> Or a least to be able to react to John Larkin's insultingly trivial
>>>>>>>> questions in a way that leaves him thinking that.
>>>>>>>>
>>>>>>>> Maybe he didn't understand the answers.
>>>>>>>
>>>>>>> You're impossible to talk too. Your only motivation is to insult.
>>>>>>
>>>>>> If your idea of a conversation is one where you get flattered nonstop,
>>>>>> I'm not the ideal conversational partner.
>>>>>>
>>>>>
>>>>> My idea of good conversation is a group of people playing with ideas
>>>>> and inventing stuff together. "Egoless" is the word, as in "egoless
>>>>> programming."
>>>>>
>>>>> https://en.wikipedia.org/wiki/Egoless_programming
>>>>>
>>>>> I don't think you can do that. Some people are too fragile.
>>>>
>>>> Your opinion is noted. I doubt if the people with whom I have
>>>> collaborated would agree.
>>>>
>>>> Sloman A.W., Buggs P., Molloy J., and Stewart D. “A
>>>> microcontroller-based driver to stabilise the temperature of an optical
>>>> stage to 1mK in the range 4C to 38C, using a Peltier heat pump and a
>>>> thermistor sensor” Measurement Science and Technology, 7 1653-64 (1996)
>>>
>>> You did one academic, unremarkable  temperature controller, published
>>> in a journal, and have cited it here maybe 50 times now. Do something
>>> new.
>>
>> I did quite a lot of stuff. That one wasn't in the least academic, and
>> it got published because I didn't have anything better to do with my
>> time immediately after I moved to the Netherlands
>>
>>> Here's my millikelven temperature controller.
>>>
>>> https://www.dropbox.com/scl/fi/emxfaurnyj35t0y84tvwl/Oven_Cables_pub.jpg?rlkey=jpcnmnt1pcooz9nj7d0j4rah0&raw=1
>>>
>>> That's a dual-stage Mach-Zender e/o modulator whose extinction is
>>> much better if the temperature is stable to milllikelvins. The big
>>> hogged-aluminum box is heated by six mosfets on the bottom, and there
>>> are four thermistors for feedback. It runs at 30C.
>>
>> Why four thermistors? The only temperature that matters is that of the
>> modulator itself. People who need to minimise temperature gradients do
>> need more than one temperature sensor, but it isn't clear why you would
>> have. I used a second thermistor to monitor the temperature of the
>> exhaust side of my Peltier cooler (which does matter) but you seem to
>> have used mosfets as resistive heaters which is rather easier.
> 
> One thermistor is on the heater board, on the bottom of the big block.
> Three are on the platform that mounts the e/o modulator. We really
> don't need three up there, but we wanted to error check and snoop for
> gradients and optionally do some averaging if we had noise.
> 
> The EOM platform is spaced off the bottom of the big block, which
> makes us a 2nd order thermal system. The main block has a 75 minute
> time constant, and the platform inside is 17 minutes. Our control
> algorithm uses the difference as, essentially, a derivative term.

We did characterise the thermal time constants of our system pretty 
carefully, as is spelled out in the paper, which does speculate on 
whether a better control algorithm would have let us achieve finer 
temperature control.

> Coolers have lots of problems, including condensation. Heating to 30C
> worked fine. This is in maybe the world's  biggest single clean room
> and the local air is always 20C.

Our machine was designed to work on biological specimens, and had to 
stabilise the specimen temperatures at industry-defined arbitrary 
levels, most of them a little  above normal room temperature. The 
customers were warned that they'd have to purge the optical path with 
dry air (usually dry nitrogen) if they set the target temperature below 
the local dew point.

The Peltier junction was unavoidable.

-- 
Bill Sloman, Sydney