Path: ...!feeds.phibee-telecom.net!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Ambient temperature control
Date: Tue, 2 Jul 2024 13:22:13 +1000
Organization: A noiseless patient Spider
Lines: 56
Message-ID: <v5vrpa$1flgu$1@dont-email.me>
References: <v5svtq$olhq$1@dont-email.me> <v5u3le$1209c$1@dont-email.me>
 <88057455-8c1e-a565-6098-7c48928fea04@electrooptical.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Tue, 02 Jul 2024 05:22:19 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="589763811335c0d4a61fb5ec4affa9f2";
	logging-data="1562142"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19TAHUxin3XhIF0qsP96rzy8hfQhPEgbj8="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:f3S0w1UXVSIcQ9iV1W6HFpg1CJE=
X-Antivirus-Status: Clean
X-Antivirus: Norton (VPS 240701-2, 1/7/2024), Outbound message
Content-Language: en-US
In-Reply-To: <88057455-8c1e-a565-6098-7c48928fea04@electrooptical.net>
Bytes: 3838

On 2/07/2024 2:24 am, Phil Hobbs wrote:
> On 2024-07-01 07:24, Martin Brown wrote:
>> On 01/07/2024 02:14, Don Y wrote:
>>> Assuming you can keep a device in its "normal operating (temperature)
>>> range", how advantageous is it (think MTBF) to drive that ambient
>>> down?  And, is there a sweet spot (as there is a cost to lowering the
>>> temperature)?
>>
>> There can be for some high performance low level OPamps. Deliberately 
>> running them as cold as is allowed helps take the LF noise floor down 
>> and by more than you would predict from Johnson noise. ISTR there was 
>> a patent for doing this back in the 1980's. Prior to that they tended 
>> to heat the front end to obtain temperature stability and low drift.
> 
> BITD you tended to get popcorn noise from ions migrating around the 
> surface and in deposited (rather than thermal) oxide.  Cooling helped 
> that a lot.  Nowadays processes are generally clean enough that you 
> don't get a lot of mobile ions.
>>
>> https://ppubs.uspto.gov/dirsearch-public/print/downloadPdf/4883957
>>
>> Made possible with the advent of decent solid state TECs.
>>>
>>> Also, is there any advantage to minimizing the hysteresis between
>>> the ACTUAL operating temperature extremes in such a control strategy
>>> (given that lower hysteresis usually comes at an increased cost)?
>>
>> Depends how temperature sensitive the thing is that you are 
>> protecting. The example I recall they were aiming for medium term 
>> stable 6 sig fig measurements with the lowest possible noise.
> 
> You don't want to use a thermostat with TECs anyway--they die very 
> rapidly, especially the soft-solder ones (Laird/Melcor).


Anybody who tries to use bang-bang control with a TEC will run into 
that. TEC's are non-linear devices, and work best when the current 
through them doesn't vary much.

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)

used a TEC, and the product didn't die in the field, or not a least over 
the roughly ten years it was on the market. My boss had had a run in 
with bang-bang control of TECs in another (earlier) product, and that 
hadn't gone well, so we were well aware of the problem (and the paper 
does go into it, briefly).

-- 
Bill Sloman, Sydney

-- 
This email has been checked for viruses by Norton antivirus software.
www.norton.com