On 9/29/2020 4:38 PM, Bob kb8tq wrote:
Hi
The gotcha with *any* SMT part is that stress / strain from the soldering
process gets into the
performance of the part for a *long* time. There is no mechanical “buffering”
in most parts. Whatever
the PCB does is what the guts of the part sees ….
Hi
The gotcha with *any* SMT part is that stress / strain from the soldering
process gets into the
performance of the part for a *long* time. There is no mechanical “buffering”
in most parts. Whatever
the PCB does is what the guts of the part sees ….
Given the popularity here on the list of
Final input from me on this topic.
The surprising, to everyone, result from the research paper referenced in the
eevblog -
https://www.eevblog.com/forum/metrology/long-term-stability-of-temperature-sensors/?action=dlattach;attach=412153
Was that the cheapest thermistor had a drift of less than
>
> Re: thermistors
* Stability of the supply/reference voltage.
>
If the reference voltage is also the reference of the ADC, its stability
and precision are much less of a concern, noise will pretty much be the
only issue.
Didier KO4BB
>
___
If one does a ratiometric measurement comparing the voltage drop across the RTD
with the voltage drop across a stable low Tc resistor connected in series with
the RTD the excitation source only needs to be quiet with good short term
stability.
Bruce
> On 29 September 2020 at 07:48 "John
I second the thermistor as the most "bang for the buck" temperature
measurement device.
My applications have not been time-nuts (or volt-nuts for that matter)
quality but even in the °C accuracy range, they are hard to beat.
Didier KO4BB
___
time-nuts
Hi
Indeed the most stable (long term) standard is a very high end RTD. These
devices have a lot of voodoo
in their design. Even with all that, they still arrive with a note on the box
that reads “ for applications requiring
< 10 mk, re-calibrate before use”. More or less, you *also* need a
Thanks for going easy on me Bob ... a case of more haste, less speed! I
focussed on low long-term drift specs without realising I had turned up a
voltage reference, sorry.
However, I have found some YSI glass encased thermistors that have long-term
drift specs of <10mK at 25C and 75C over a
I checked my 3456A with a Beckman resistance standard box. A 5000 Ohm
resistor is measured as 25.02 degrees Celsius, which is good considering
neither the 3456A or the Beckman have been calibrated in ages.
I have 10 of the Ametherm ACC-003s on order from DigiKey. When they show up
(and if we
time and frequency measurement
Subject: Re: [time-nuts] What do people use for measuring temperature?
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Hi
One interesting ?oops? using RTD?s:
They are close cousins of strain
> Answered my own question: Ametherm ACC-003 from Tim Hughesâ 2-02-2019 post
> to
> the HPAK Equipment group (thanks, Tim!).
Thanks.
I poked around a bit. Ametherm's data sheet shows that they make them in
various resistances and also various accuracies. 003 and friends are 5K.
ACC-003
Hi
You would need to find a temperature sensor rather than a voltage reference…. :)
The AD590 still seems to be considered a pretty good device after all these
years. If there is long
term data in the spec sheet, I did not spot it in a quick read. Based on what
we saw back in the 1970’s
(which
Would not a band-gap temperature sensor such as the LT6657 be better than a
thermistor for precision, low drift applications?
The above device has 30 ppm/√kHr long-term drift. That should hold a mk for a
fair few years.
John
Hi
> On Sep 27, 2020, at 11:59 AM, Jeremy Nichols wrote:
>
>>
>>
>>
>>> We used three thermistors and averaged them.
>>
>> I assume they were spread around in case one side of the package was
>> warmer than the other.
>>
>
>> Could one do an analog “average” by using a set of, for
>
>
>
> > We used three thermistors and averaged them.
>
> I assume they were spread around in case one side of the package was
> warmer than the other.
>
> Could one do an analog “average” by using a set of, for example, four
‘identical’ (there’s a risky word!) thermistors in series-parallel?
> The HP E1938A OCXO that I worked on had a feature where we could set the oven
> temperature individually on each oscillator to the exact turnover point of
> the crystal.
How accurately did you set it?
> We used three thermistors and averaged them.
I assume they were spread around in case
Do we know what this “Long Term Aging Process” is or is it proprietary?
On Sat, Sep 26, 2020 at 5:03 PM Bruce Griffiths
wrote:
> Drift ~1-2mK per year for suitably conditioned thermistors at 25C:
>
>
>
Drift ~1-2mK per year for suitably conditioned thermistors at 25C:
https://www.littelfuse.com/technical-resources/technical-centers/temperature-sensors/thermistor-info/thermistor-terminology/stability.aspx
Bruce
> On 27 September 2020 at 11:15 Bob kb8tq wrote:
>
>
> Hi
>
> Roughly speaking
The HP E1938A OCXO that I worked on had a feature where
we could set the oven temperature individually on each
oscillator to the exact turnover point of the crystal.
With all the temperature characterization we did, it
would seem like if there were a thermistor "aging"
process, we would have seen
Hi
Roughly speaking 99.9% of all OCXO’s use thermistors as temperature
sensors.
The normal evaluation process on a new one *probably* would catch something <
0.01C
over a few months. You may do it a couple different ways depending on the target
OCXO. The net result is still in the “golly
Have any time-nuts got any data on the long term stability or drift
rates/ageing characteristics of thermistors? I am concerned with ability of
holding temperature constant at the milliK level for years. I reckon that if
one can measure it one can control it. Conversely if one can't measure
Answered my own question: Ametherm ACC-003 from Tim Hughes’ 2-02-2019 post
to the HPAK Equipment group (thanks, Tim!).
On Sat, Sep 26, 2020 at 10:25 AM Jeremy Nichols wrote:
> The HP-3456A DVM was mentioned as one way to measure temperature with
> thermistors. Does anyone know the specs for
The HP-3456A DVM was mentioned as one way to measure temperature with
thermistors. Does anyone know the specs for the thermistor that the 3456
can use? All my manual gives is an HP part number.
Jeremy
--
Jeremy Nichols
Sent from my iPad 6.
___
e: 8
>> Date: Fri, 25 Sep 2020 04:50:35 -0700
>> From: Hal Murray
>> To: time-nuts@lists.febo.com
>> Cc: Hal Murray
>> Subject: [time-nuts] What do people use for measuring temperature?
>> Message-ID:
>> <20200925115035.504af406...@ip-64-139-1-69.sj
ray
> Subject: [time-nuts] What do people use for measuring temperature?
> Message-ID:
> <20200925115035.504af406...@ip-64-139-1-69.sjc.megapath.net>
> Content-Type: text/plain; charset=us-ascii
>
>
> I've got a collection of 1-wire gizmos and USB thumb drives. Th
Hi
Going back a bit to get closer to the original request …..
Indeed a thermistor is the “high resolution” king of the hill when it comes to
temperature
measurement. Resistance change of 3% (30,000 ppm) per degree is not uncommon,
you can do better …
They come in all sorts of packages for not
A thermistor should do the job. You can buy them in SMD packages and
down to 0.1% accuracy.
How much resolution you get depends on the measurement range and the
ADC you are using.
A platinum RTD would be another candidate but requires more signal
conditioning.
In 3-wire or 4-wire probe
This is the document and the correct P/N that Bert meant:
Application Note 3
Applications for a Switched-Capacitor Instrumentation Building Block
Jim Williams, July 1985
page AN3-6, Precision, Linearized Platinum RTD Signal Conditioner
We use a LTC 1013 see LTC Application Note 3 page 6 at least 0.05 C. Good
enough for us. May still have a board would have to find it, Contact me off
list. Bert Kehren. In a message dated 9/25/2020 10:46:34 PM Eastern Standard
Time, hmur...@megapathdsl.net writes:
I've got a collection of
>From I know from measuring voltage references getting linearity in those
kinds of temp ranges not only requires really good sensors but often it
needs to be thermally bonded to what's being measured and often with some
block of material that's makes swings in temperature much more subtle.
Even a
It would appear that the HP 3456A in temperature mode would meet your needs.
The 5k thermistor is very cheap. The temperature resolution is very small, as
I recall perhaps 0.001 degree but not sure. You can log manually or via GPIB.
Don't think its accuracy is anywhere near its resolution
I've got a collection of 1-wire gizmos and USB thumb drives. They are great
for many applications but I'm looking for something better/different.
I'd like something that reads to 0.01 degree or 0.001 degree. I don't need
accuracy. What I want is reasonable linearity so I can make pretty
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