Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Poul-Henning Kamp]

In message 
, "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:

>I can't find it now, but I know someone said thermocouples are obsolete. I
>spoke to a friend tonight who services industrial boilders. He said
>thermocouples are far from obsolesce, at temperatures of a few hundred deg
>C, as nothing else works.

Thermocouples are not obsolete.

If nothing else because they are cheap and can be made on the spot and
in all sorts of weird shapes.

The only thing which competes with thermocouples in high temperature
is platinum, which is horribly expensive by comparison and more
prone to noise than thermocouples.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 5 June 2017 at 00:59, Attila Kinali  wrote:

> Moin,
>
> This discussion is kind of getting heated.
> Let's put some facts in, to steer it away from
> opinion based discussion.
>

I can't find it now, but I know someone said thermocouples are obsolete. I
spoke to a friend tonight who services industrial boilders. He said
thermocouples are far from obsolesce, at temperatures of a few hundred deg
C, as nothing else works.


Dave
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Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Bruce Griffiths]

Additional info/papers on Thermistor stability:

http://www.digikey.com/en/pdf/u/us-sensor/us-sensor-stability-long-term-aging

https://www.thermistor.com/sites/default/files/specsheets/T150-Series-Stability.pdf

https://www.vishay.com/docs/49498/ntcs-e3-smt_vmn-pt0283.pdf

>From LIGO:

http://www.aspe.net/publications/Annual_2008/POSTERS/08UNCER/2643.PDF

Bruce


> 
> On 06 June 2017 at 09:49 Bruce Griffiths  
> wrote:
> 
> Here's a NIST paper on Thermistor stability:
> 
> http://nvlpubs.nist.gov/nistpubs/jres/83/jresv83n3p247_A1b.pdf
> 
> Bruce
> 
> > > 
> > On 06 June 2017 at 01:45 Bob kb8tq  wrote:
> > 
> > Hi
> > 
> > Well, as part of the process of designing them into OCXO’s you do 
> > indeed check their long term stability.
> > The test is done in an indirect fashion so you only come up with a 
> > “it’s below the limit” sort of number. The
> > typical process involves running a group of OCXO’s on turn to check 
> > the frequency and then shifting them
> > off turn to make a sort of thermometer. After a few months of 
> > frequency readings you take them back to turn
> > for a while. Relative frequency shift math gives you a stability 
> > number for the thermistor and the rest of the
> > circuitry. You may repeat the run for months / shift process a 
> > couple of times. If the answer isn’t “I can’t see
> > a difference” you look for a new thermistor. Since it’s a long 
> > drawn out test, the tendency is to stick with a
> > vendor’s part for quite a while. The parts also tend to be design 
> > specific so what works in my (say SMT)
> > design may not work well in your (say chip and wire) design.
> > 
> > Bob
> > 
> > > > > 
> > > > > > > 
> > > > On Jun 5, 2017, at 9:20 AM, romeo987 
> > > >  wrote:
> > > > 
> > > > > > > 
> > > Hi, guys
> > > I have been following time nuts and volt nuts for some time 
> > > out of interest and fascination. Although my personal backyard hobby is 
> > > more along a volt nuts line, the two worlds often collide - like in this 
> > > discussion of temperature sensors, and in particular their long term 
> > > stability. NTC thermistors appear to be very commonly used in ovens used 
> > > to stabilize voltage references (solid state as well as chemical) . I 
> > > have long wondered about their stability. If, as Bruce asserts, "high 
> > > quality thermistors can achieve drifts of around 1mK/month" then it 
> > > appears that this level of drift is a significant factor in the 
> > > "apparent" aging of, say, a bank of Weston cells (which is still my best 
> > > backyard shot at a voltage reference).
> > > 
> > > I have had no luck with Google; Bruce's statement is the 
> > > first quantified allusion that I have seen to this subject. Is there any 
> > > actual data available on the long term performance of NTC sensors?
> > > 
> > > Roman
> > > 
> > > > > > > 
> > > > > > > > > 
> > > > > > > > > > > 
> > > > > > On 5 Jun 2017, at 9:53 AM, Bruce Griffiths 
> > > > > >  wrote:
> > > > > > 
> > > > > > > > > > > 
> > > > > > > > > 
> > > > The other issue that needs to be considered is the 
> > > > drift in temperature sensor characteristics when operated at a constant 
> > > > temperature (as is typical in a continuously operated crystal oven). 
> > > > High quality thermistors can achieve drifts of around 1mK/month. Its 
> > > > unlikely that something as complex as an AD590 will achieve a similar 
> > > > drift (1nA/month in a operating current of 300uA or so at 25C). High 
> > > > quality PRT sensors drift even less than thermistors when operating at 
> > > > constant temperature.
> > > > 
> > > > Bruce
> > > > 
> > > > > > > > > 
> > > > > > > > > > > 
> > > > > > > > > > > > > 
> > > > > > > > > > > > > > > 
> > > > > > > > .On 05 June 2017 at 11:59 
> > > > > > > > Attila Kinali  wrote:
> > > > > > > > 
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > 
> > > > > > > > > > > 
> > > > > Moin,
> > > > > 
> > > > > This discussion is kind of getting heated.
> > > > > Let's put some facts in, to steer it away from
> > > > > opinion based discussion.
> > > > > 
> > > > > On Sun, 4 Jun 2017 08:44:33 -0700
> > > > > "Donald E. Pauly"  

Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Bruce Griffiths]

Here's a NIST paper on Thermistor stability:

http://nvlpubs.nist.gov/nistpubs/jres/83/jresv83n3p247_A1b.pdf

Bruce

> 
> On 06 June 2017 at 01:45 Bob kb8tq  wrote:
> 
> Hi
> 
> Well, as part of the process of designing them into OCXO’s you do indeed 
> check their long term stability.
> The test is done in an indirect fashion so you only come up with a “it’s 
> below the limit” sort of number. The
> typical process involves running a group of OCXO’s on turn to check the 
> frequency and then shifting them
> off turn to make a sort of thermometer. After a few months of frequency 
> readings you take them back to turn
> for a while. Relative frequency shift math gives you a stability number 
> for the thermistor and the rest of the
> circuitry. You may repeat the run for months / shift process a couple of 
> times. If the answer isn’t “I can’t see
> a difference” you look for a new thermistor. Since it’s a long drawn out 
> test, the tendency is to stick with a
> vendor’s part for quite a while. The parts also tend to be design 
> specific so what works in my (say SMT)
> design may not work well in your (say chip and wire) design.
> 
> Bob
> 
> > > 
> > On Jun 5, 2017, at 9:20 AM, romeo987  
> > wrote:
> > 
> > Hi, guys
> > I have been following time nuts and volt nuts for some time out of 
> > interest and fascination. Although my personal backyard hobby is more along 
> > a volt nuts line, the two worlds often collide - like in this discussion of 
> > temperature sensors, and in particular their long term stability. NTC 
> > thermistors appear to be very commonly used in ovens used to stabilize 
> > voltage references (solid state as well as chemical) . I have long wondered 
> > about their stability. If, as Bruce asserts, "high quality thermistors can 
> > achieve drifts of around 1mK/month" then it appears that this level of 
> > drift is a significant factor in the "apparent" aging of, say, a bank of 
> > Weston cells (which is still my best backyard shot at a voltage reference).
> > 
> > I have had no luck with Google; Bruce's statement is the first 
> > quantified allusion that I have seen to this subject. Is there any actual 
> > data available on the long term performance of NTC sensors?
> > 
> > Roman
> > 
> > > > > 
> > > On 5 Jun 2017, at 9:53 AM, Bruce Griffiths 
> > >  wrote:
> > > 
> > > The other issue that needs to be considered is the drift in 
> > > temperature sensor characteristics when operated at a constant 
> > > temperature (as is typical in a continuously operated crystal oven). High 
> > > quality thermistors can achieve drifts of around 1mK/month. Its unlikely 
> > > that something as complex as an AD590 will achieve a similar drift 
> > > (1nA/month in a operating current of 300uA or so at 25C). High quality 
> > > PRT sensors drift even less than thermistors when operating at constant 
> > > temperature.
> > > 
> > > Bruce
> > > 
> > > > > > > 
> > > > .On 05 June 2017 at 11:59 Attila Kinali 
> > > >  wrote:
> > > > 
> > > > Moin,
> > > > 
> > > > This discussion is kind of getting heated.
> > > > Let's put some facts in, to steer it away from
> > > > opinion based discussion.
> > > > 
> > > > On Sun, 4 Jun 2017 08:44:33 -0700
> > > > "Donald E. Pauly"  wrote:
> > > > 
> > > > > > > > > 
> > > > > I stand by my remark that thermistors have been 
> > > > > obsolete for over 40
> > > > > years. The only exception that I know of is 
> > > > > cesium beam tubes that
> > > > > must withstand a 350° C bakeout. Thermistors are 
> > > > > unstable and
> > > > > manufactured with a witches brew straight out of 
> > > > > MacBeth. Their
> > > > > output voltages are tiny and are they 
> > > > > inconvenient to use at different
> > > > > temperatures.
> > > > > 
> > > > > If you really mean thermistors, and not, as Bob 
> > > > > suggested thermocouples,
> > > > > then I have to disagree. The most stable 
> > > > > temperature sensors are
> > > > > platinum wire sensors. The standards class PRT's 
> > > > > are the gold standard
> > > > > when it comes to temperature measurement, for a 
> > > > > quite wide range
> > > > > (-260°C to +960°C) and are considered very 
> > > > > stable. They offer (absolute)
> > > > > accuracies in the order of 10mK in the 
> > > > > temperature range below 400°C.
> > > > > Even industrial grade PRT sensors 

Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Poul-Henning Kamp]

In message <20170605133013.526e8505158e68b6a8091...@kinali.ch>, Attila Kinali w
rites:

>> Where do digital sensors (e.g. ds1820 and some more recent parts from TI)
>> fit into this ?
>
>AFAIK, these are all band-gap temperature sensors. 

The Ds1820 is based on the frequency difference between two
free-running silicon oscillators with different physical design.


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Bob kb8tq]

Hi

Well, as part of the process of designing them into OCXO’s you do indeed check 
their long term stability. 
The test is done in an indirect fashion so you only come up with a “it’s below 
the limit” sort of number. The
typical process involves running a group of OCXO’s on turn to check the 
frequency and then shifting them
off turn to make a sort of thermometer. After a few months of frequency 
readings you take them back to turn 
for a while. Relative frequency shift math gives you a stability number for the 
thermistor and the rest of the
circuitry. You may repeat the run for months / shift process a couple of times. 
If the answer isn’t “I can’t see 
a difference” you look for a new thermistor. Since it’s a long drawn out test, 
the tendency is to stick with a 
vendor’s part for quite a while. The parts also tend to be design specific so 
what works in my (say SMT)
design may not work well in your (say chip and wire) design. 

Bob

> On Jun 5, 2017, at 9:20 AM, romeo987  wrote:
> 
> Hi, guys
> I have been following time nuts and volt nuts for some time out of interest 
> and fascination. Although my personal backyard hobby is more along a volt 
> nuts line, the two worlds often collide - like in this discussion of 
> temperature sensors, and in particular their long term stability. NTC 
> thermistors appear to be very commonly used in ovens used to stabilize 
> voltage references (solid state as well as chemical) . I have long wondered 
> about their stability.  If, as Bruce asserts, "high quality thermistors can 
> achieve drifts of around 1mK/month" then it appears that this level of drift 
> is a significant factor in the "apparent" aging of, say, a bank of Weston 
> cells (which is still my best backyard shot at a voltage reference). 
> 
> I have had no luck with Google; Bruce's statement is the first quantified 
> allusion that I have seen to this subject.  Is there any actual data 
> available on the long term performance of NTC sensors?
> 
> Roman
> 
>> On 5 Jun 2017, at 9:53 AM, Bruce Griffiths  
>> wrote:
>> 
>> The other issue that needs to be considered is the drift in temperature 
>> sensor characteristics when operated at a constant temperature (as is 
>> typical in a continuously operated crystal oven). High quality thermistors 
>> can achieve drifts of around 1mK/month. Its unlikely that something as 
>> complex as an AD590 will achieve a similar drift (1nA/month in a operating 
>> current of 300uA or so at 25C). High quality PRT sensors drift even less 
>> than thermistors when operating at constant temperature.
>> 
>> Bruce
>> 
>>> 
>>>   .On 05 June 2017 at 11:59 Attila Kinali  wrote:
>>> 
>>>   Moin,
>>> 
>>>   This discussion is kind of getting heated.
>>>   Let's put some facts in, to steer it away from
>>>   opinion based discussion.
>>> 
>>>   On Sun, 4 Jun 2017 08:44:33 -0700
>>>   "Donald E. Pauly"  wrote:
>>> 
   I stand by my remark that thermistors have been obsolete for over 40
   years. The only exception that I know of is cesium beam tubes that
   must withstand a 350° C bakeout. Thermistors are unstable and
   manufactured with a witches brew straight out of MacBeth. Their
   output voltages are tiny and are they inconvenient to use at 
 different
   temperatures.
 
>>>   If you really mean thermistors, and not, as Bob suggested thermocouples,
>>>   then I have to disagree. The most stable temperature sensors are
>>>   platinum wire sensors. The standards class PRT's are the gold standard
>>>   when it comes to temperature measurement, for a quite wide range
>>>   (-260°C to +960°C) and are considered very stable. They offer (absolute)
>>>   accuracies in the order of 10mK in the temperature range below 400°C.
>>>   Even industrial grade PRT sensors give you an absolute accuracy better
>>>   than 0.1K up to 200-300°C. The "cheap" PT100 are more of the order of 
>>> 1-10°C
>>>   accuracy... all numbers just using a two-point calibration.
>>> 
>>>   For more information on this see [1] chapter 6 and [2] for industrial 
>>> sensors.
>>> 
>>>   NTC sensors have a higher variablity of their parameters in production
>>>   and are usually specified in % of temperature relative to their reference
>>>   point, which is usually 25°C. Typical values are 0.1% to 5%. Additionally
>>>   there is a deviation from the reference point, specified in °C, which
>>>   is usually in the order of 0.1°C to 1°C.
>>> 
>>>   The NTC sensors are less accurate than PT sensors, but offer the advantage
>>>   of higher resistance (thus lower self-heating), higher slope (thus better
>>>   precision). Biggest disadvantage is their non-linear curve. Their price
>>>   is also a fraction of PT sensors and due to that you can have them in
>>>   many different forms, from the 0201 SMD resistor, to a large stainless
>>>   steal pipe that goes into a chemical 

Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[romeo987]

Hi, guys
I have been following time nuts and volt nuts for some time out of interest and 
fascination. Although my personal backyard hobby is more along a volt nuts 
line, the two worlds often collide - like in this discussion of temperature 
sensors, and in particular their long term stability. NTC thermistors appear to 
be very commonly used in ovens used to stabilize voltage references (solid 
state as well as chemical) . I have long wondered about their stability.  If, 
as Bruce asserts, "high quality thermistors can achieve drifts of around 
1mK/month" then it appears that this level of drift is a significant factor in 
the "apparent" aging of, say, a bank of Weston cells (which is still my best 
backyard shot at a voltage reference). 

I have had no luck with Google; Bruce's statement is the first quantified 
allusion that I have seen to this subject.  Is there any actual data available 
on the long term performance of NTC sensors?

Roman

> On 5 Jun 2017, at 9:53 AM, Bruce Griffiths  wrote:
> 
> The other issue that needs to be considered is the drift in temperature 
> sensor characteristics when operated at a constant temperature (as is typical 
> in a continuously operated crystal oven). High quality thermistors can 
> achieve drifts of around 1mK/month. Its unlikely that something as complex as 
> an AD590 will achieve a similar drift (1nA/month in a operating current of 
> 300uA or so at 25C). High quality PRT sensors drift even less than 
> thermistors when operating at constant temperature.
> 
> Bruce
> 
>> 
>>.On 05 June 2017 at 11:59 Attila Kinali  wrote:
>> 
>>Moin,
>> 
>>This discussion is kind of getting heated.
>>Let's put some facts in, to steer it away from
>>opinion based discussion.
>> 
>>On Sun, 4 Jun 2017 08:44:33 -0700
>>"Donald E. Pauly"  wrote:
>> 
>>>I stand by my remark that thermistors have been obsolete for over 40
>>>years. The only exception that I know of is cesium beam tubes that
>>>must withstand a 350° C bakeout. Thermistors are unstable and
>>>manufactured with a witches brew straight out of MacBeth. Their
>>>output voltages are tiny and are they inconvenient to use at 
>>> different
>>>temperatures.
>>> 
>>If you really mean thermistors, and not, as Bob suggested thermocouples,
>>then I have to disagree. The most stable temperature sensors are
>>platinum wire sensors. The standards class PRT's are the gold standard
>>when it comes to temperature measurement, for a quite wide range
>>(-260°C to +960°C) and are considered very stable. They offer (absolute)
>>accuracies in the order of 10mK in the temperature range below 400°C.
>>Even industrial grade PRT sensors give you an absolute accuracy better
>>than 0.1K up to 200-300°C. The "cheap" PT100 are more of the order of 
>> 1-10°C
>>accuracy... all numbers just using a two-point calibration.
>> 
>>For more information on this see [1] chapter 6 and [2] for industrial 
>> sensors.
>> 
>>NTC sensors have a higher variablity of their parameters in production
>>and are usually specified in % of temperature relative to their reference
>>point, which is usually 25°C. Typical values are 0.1% to 5%. Additionally
>>there is a deviation from the reference point, specified in °C, which
>>is usually in the order of 0.1°C to 1°C.
>> 
>>The NTC sensors are less accurate than PT sensors, but offer the advantage
>>of higher resistance (thus lower self-heating), higher slope (thus better
>>precision). Biggest disadvantage is their non-linear curve. Their price
>>is also a fraction of PT sensors and due to that you can have them in
>>many different forms, from the 0201 SMD resistor, to a large stainless
>>steal pipe that goes into a chemical tank. NTCs are the workhorse in
>>todays temperature measurement and control designs.
>> 
>>The next category are band-gap sensors like the AD590. Their biggest
>>advantage is that their 0 point is fix at 0K (and very accurately so).
>>Ie they can be used with single point calibration and achieve 1°C accuracy
>>this way. Their biggest drawback their large thermal mass and large
>>insulating case, because they are basically an standard, analog IC.
>>Ie their main use is in devices where there is a lot of convection and
>>slow temperature change. Due to their simple and and quite linear
>>characteristics, they are often used in purely analog temperature
>>control circuits, or where a linearization is not feasible.
>>But only if price isn't an issue (they cost 10-1000 times as
>>much as an PTC). Their biggest disadvantage, beside their slow
>>thermal raction time, is their large noise uncorrelated to the
>>supply voltage, and thus cannot be compensated by ratiometric measurement.
>>They are also more suceptible to 

Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Bob kb8tq]

Hi

> On Jun 5, 2017, at 7:30 AM, Attila Kinali  wrote:
> 
> On Mon, 5 Jun 2017 01:18:59 +0100
> Adrian Godwin  wrote:
> 
>> Where do digital sensors (e.g. ds1820 and some more recent parts from TI)
>> fit into this ?
> 
> AFAIK, these are all band-gap temperature sensors. But unlike a discrete
> sensor, you have the problem that they only contain a low resolution
> ADC on die (somewhere between 8 and 14 bit). If your goal is to measure
> temperature and report it with an accuracy of about 1°C, then these are
> the easiest to use sensors you can buy. Sensor noise doesn't really matter
> with them, as it is dominated by the low ADC resolution. I don't have any
> long term stability data on those, but given their use-case I do not think
> that they are very stable.

Based on using them in a lot of designs, they are indeed quite stable. They are 
not
going to rival a thermistor or an RTD, but compared to their resolution they 
are stable. 
Put another way, if they read out at the (say) 0.5 C level, you can come back a 
year later 
and the temperature repeats at < the 0.5 C level. 

None of this is simple or straightforward. All temperature sensors have a 
sensitivity 
to strain. They all exhibit some level of hysteresis.  That can make aging 
measurements 
a bit challenging. 

Bob


> Although long term stability might not be an
> issue at all, again due to low ADC resolution.
> 
> 
> If you need better precision, accuracy, or stability, then choosing one
> of the modern delta-sigma ADCs that directly support thermistors
> (e.g. like AD7124) is not much more difficult, though a bit more expensive
> (around 10USD instead of 5USD like for an TMP107). Additionally you need
> to calbirate the system, which means you need a reference temperature sensor
> and a setup with which you can produce different temperatures. Though for
> an oven kind of temperature control, one can live without calibration.
> 
> 
>   Attila Kinali
> -- 
> You know, the very powerful and the very stupid have one thing in common.
> They don't alters their views to fit the facts, they alter the facts to
> fit the views, which can be uncomfortable if you happen to be one of the
> facts that needs altering.  -- The Doctor
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Attila Kinali]

On Mon, 5 Jun 2017 01:18:59 +0100
Adrian Godwin  wrote:

> Where do digital sensors (e.g. ds1820 and some more recent parts from TI)
> fit into this ?

AFAIK, these are all band-gap temperature sensors. But unlike a discrete
sensor, you have the problem that they only contain a low resolution
ADC on die (somewhere between 8 and 14 bit). If your goal is to measure
temperature and report it with an accuracy of about 1°C, then these are
the easiest to use sensors you can buy. Sensor noise doesn't really matter
with them, as it is dominated by the low ADC resolution. I don't have any
long term stability data on those, but given their use-case I do not think
that they are very stable. Although long term stability might not be an
issue at all, again due to low ADC resolution.


If you need better precision, accuracy, or stability, then choosing one
of the modern delta-sigma ADCs that directly support thermistors
(e.g. like AD7124) is not much more difficult, though a bit more expensive
(around 10USD instead of 5USD like for an TMP107). Additionally you need
to calbirate the system, which means you need a reference temperature sensor
and a setup with which you can produce different temperatures. Though for
an oven kind of temperature control, one can live without calibration.


Attila Kinali
-- 
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering.  -- The Doctor
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Bob kb8tq]

Hi

If your objective is a resolution of < 0.001 C at something < 1 second, the 
current crop of 
digital sensors don’t quite do what you need to do. They are a terrific way to 
do wide range 
measurements that might feed into some sort of correction algorithm. A 
conventional 
thermistor bridge falls apart if you try to run it -55 to +125. The range of 
resistances 
involved results in significantly lowered resolution at the end(s) of the 
range. 

Bob

> On Jun 4, 2017, at 8:18 PM, Adrian Godwin  wrote:
> 
> Where do digital sensors (e.g. ds1820 and some more recent parts from TI)
> fit into this ?
> 
> 
> On Mon, Jun 5, 2017 at 12:59 AM, Attila Kinali  wrote:
> 
>> Moin,
>> 
>> This discussion is kind of getting heated.
>> Let's put some facts in, to steer it away from
>> opinion based discussion.
>> 
>> On Sun, 4 Jun 2017 08:44:33 -0700
>> "Donald E. Pauly"  wrote:
>> 
>>> I stand by my remark that thermistors have been obsolete for over 40
>>> years.  The only exception that I know of is cesium beam tubes that
>>> must withstand a 350° C bakeout.  Thermistors are unstable and
>>> manufactured with a witches brew straight out of MacBeth.  Their
>>> output voltages are tiny and are they inconvenient to use at different
>>> temperatures.
>> 
>> If you really mean thermistors, and not, as Bob suggested thermocouples,
>> then I have to disagree. The most stable temperature sensors are
>> platinum wire sensors. The standards class PRT's are the gold standard
>> when it comes to temperature measurement, for a quite wide range
>> (-260°C to +960°C) and are considered very stable. They offer (absolute)
>> accuracies in the order of 10mK in the temperature range below 400°C.
>> Even industrial grade PRT sensors give you an absolute accuracy better
>> than 0.1K up to 200-300°C. The "cheap" PT100 are more of the order of
>> 1-10°C
>> accuracy... all numbers just using a two-point calibration.
>> 
>> For more information on this see [1] chapter 6 and [2] for industrial
>> sensors.
>> 
>> NTC sensors have a higher variablity of their parameters in production
>> and are usually specified in % of temperature relative to their reference
>> point, which is usually 25°C. Typical values are 0.1% to 5%. Additionally
>> there is a deviation from the reference point, specified in °C, which
>> is usually in the order of 0.1°C to 1°C.
>> 
>> The NTC sensors are less accurate than PT sensors, but offer the advantage
>> of higher resistance (thus lower self-heating), higher slope (thus better
>> precision). Biggest disadvantage is their non-linear curve. Their price
>> is also a fraction of PT sensors and due to that you can have them in
>> many different forms, from the 0201 SMD resistor, to a large stainless
>> steal pipe that goes into a chemical tank. NTCs are the workhorse in
>> todays temperature measurement and control designs.
>> 
>> The next category are band-gap sensors like the AD590. Their biggest
>> advantage is that their 0 point is fix at 0K (and very accurately so).
>> Ie they can be used with single point calibration and achieve 1°C accuracy
>> this way. Their biggest drawback their large thermal mass and large
>> insulating case, because they are basically an standard, analog IC.
>> Ie their main use is in devices where there is a lot of convection and
>> slow temperature change. Due to their simple and and quite linear
>> characteristics, they are often used in purely analog temperature
>> control circuits, or where a linearization is not feasible.
>> But only if price isn't an issue (they cost 10-1000 times as
>> much as an PTC). Their biggest disadvantage, beside their slow
>> thermal raction time, is their large noise uncorrelated to the
>> supply voltage, and thus cannot be compensated by ratiometric measurement.
>> They are also more suceptible to mechanical stress than NTC's and PT's,
>> due to their construction. Similar to voltage references (which they
>> actually are), their aging is quite substantial and cannot be neglected
>> in precision application.
>> With a 3 point calibration, better than 0.5°C accuracy can be achieved
>> (modulo aging) within their operating temperature range, which is
>> rather limited, compared to the other sensor types.
>> 
>> I don't know enough about thermocouples to say much about them, beside
>> that they are cumbersome to work with (e.g. the cold contact) and
>> produce a low voltage (several µV) output with quite high impedance,
>> which makes the analog electronics difficult to design as well.
>> 
>> 
>> With todays electronics, the easiest sensors to work with are NTC and
>> PT100/PT1000 as most high resolution delta-sigma ADCs have direct support
>> for 3 and/or 4 wire measurement of those, including compensation for
>> reference voltage/current variation. Using a uC as control element
>> also opens up the possibility to linearize the curve of NTCs without
>> loss of accuracy. Usually measurement 

Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Adrian Godwin]

Where do digital sensors (e.g. ds1820 and some more recent parts from TI)
fit into this ?


On Mon, Jun 5, 2017 at 12:59 AM, Attila Kinali  wrote:

> Moin,
>
> This discussion is kind of getting heated.
> Let's put some facts in, to steer it away from
> opinion based discussion.
>
> On Sun, 4 Jun 2017 08:44:33 -0700
> "Donald E. Pauly"  wrote:
>
> > I stand by my remark that thermistors have been obsolete for over 40
> > years.  The only exception that I know of is cesium beam tubes that
> > must withstand a 350° C bakeout.  Thermistors are unstable and
> > manufactured with a witches brew straight out of MacBeth.  Their
> > output voltages are tiny and are they inconvenient to use at different
> > temperatures.
>
> If you really mean thermistors, and not, as Bob suggested thermocouples,
> then I have to disagree. The most stable temperature sensors are
> platinum wire sensors. The standards class PRT's are the gold standard
> when it comes to temperature measurement, for a quite wide range
> (-260°C to +960°C) and are considered very stable. They offer (absolute)
> accuracies in the order of 10mK in the temperature range below 400°C.
> Even industrial grade PRT sensors give you an absolute accuracy better
> than 0.1K up to 200-300°C. The "cheap" PT100 are more of the order of
> 1-10°C
> accuracy... all numbers just using a two-point calibration.
>
> For more information on this see [1] chapter 6 and [2] for industrial
> sensors.
>
> NTC sensors have a higher variablity of their parameters in production
> and are usually specified in % of temperature relative to their reference
> point, which is usually 25°C. Typical values are 0.1% to 5%. Additionally
> there is a deviation from the reference point, specified in °C, which
> is usually in the order of 0.1°C to 1°C.
>
> The NTC sensors are less accurate than PT sensors, but offer the advantage
> of higher resistance (thus lower self-heating), higher slope (thus better
> precision). Biggest disadvantage is their non-linear curve. Their price
> is also a fraction of PT sensors and due to that you can have them in
> many different forms, from the 0201 SMD resistor, to a large stainless
> steal pipe that goes into a chemical tank. NTCs are the workhorse in
> todays temperature measurement and control designs.
>
> The next category are band-gap sensors like the AD590. Their biggest
> advantage is that their 0 point is fix at 0K (and very accurately so).
> Ie they can be used with single point calibration and achieve 1°C accuracy
> this way. Their biggest drawback their large thermal mass and large
> insulating case, because they are basically an standard, analog IC.
> Ie their main use is in devices where there is a lot of convection and
> slow temperature change. Due to their simple and and quite linear
> characteristics, they are often used in purely analog temperature
> control circuits, or where a linearization is not feasible.
> But only if price isn't an issue (they cost 10-1000 times as
> much as an PTC). Their biggest disadvantage, beside their slow
> thermal raction time, is their large noise uncorrelated to the
> supply voltage, and thus cannot be compensated by ratiometric measurement.
> They are also more suceptible to mechanical stress than NTC's and PT's,
> due to their construction. Similar to voltage references (which they
> actually are), their aging is quite substantial and cannot be neglected
> in precision application.
> With a 3 point calibration, better than 0.5°C accuracy can be achieved
> (modulo aging) within their operating temperature range, which is
> rather limited, compared to the other sensor types.
>
> I don't know enough about thermocouples to say much about them, beside
> that they are cumbersome to work with (e.g. the cold contact) and
> produce a low voltage (several µV) output with quite high impedance,
> which makes the analog electronics difficult to design as well.
>
>
> With todays electronics, the easiest sensors to work with are NTC and
> PT100/PT1000 as most high resolution delta-sigma ADCs have direct support
> for 3 and/or 4 wire measurement of those, including compensation for
> reference voltage/current variation. Using a uC as control element
> also opens up the possibility to linearize the curve of NTCs without
> loss of accuracy. Usually measurement precision, with a state-of-the-art
> circuit, is limited by noise coupling into the leads of the sensor
> and noise in and around the ADC. (see [3-5])
>
>
> > Where did you get the idea to use a 1 k load for an AD590?
>
> Jim was refering to a circuit _he_ used in a satellite. Not to your
> circuit.
>
> > The room temperature coefficient of an AT crystal is -cd 100 ppb per
> > reference cut angle in minutes.  (-600 ppb/C° for standard crystal)
> > The practical limit in a crystal designed for room temperature is
> > about 0.1' cut accuracy or ±10 ppb/C°.  If you have access to an
> > atomic standard, you can use feed forward 

Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Bruce Griffiths]

The other issue that needs to be considered is the drift in temperature sensor 
characteristics when operated at a constant temperature (as is typical in a 
continuously operated crystal oven). High quality thermistors can achieve 
drifts of around 1mK/month. Its unlikely that something as complex as an AD590 
will achieve a similar drift (1nA/month in a operating current of 300uA or so 
at 25C). High quality PRT sensors drift even less than thermistors when 
operating at constant temperature.

Bruce

> 
> .On 05 June 2017 at 11:59 Attila Kinali  wrote:
> 
> Moin,
> 
> This discussion is kind of getting heated.
> Let's put some facts in, to steer it away from
> opinion based discussion.
> 
> On Sun, 4 Jun 2017 08:44:33 -0700
> "Donald E. Pauly"  wrote:
> 
> > > 
> > I stand by my remark that thermistors have been obsolete for over 40
> > years. The only exception that I know of is cesium beam tubes that
> > must withstand a 350° C bakeout. Thermistors are unstable and
> > manufactured with a witches brew straight out of MacBeth. Their
> > output voltages are tiny and are they inconvenient to use at 
> > different
> > temperatures.
> > 
> > > 
> If you really mean thermistors, and not, as Bob suggested thermocouples,
> then I have to disagree. The most stable temperature sensors are
> platinum wire sensors. The standards class PRT's are the gold standard
> when it comes to temperature measurement, for a quite wide range
> (-260°C to +960°C) and are considered very stable. They offer (absolute)
> accuracies in the order of 10mK in the temperature range below 400°C.
> Even industrial grade PRT sensors give you an absolute accuracy better
> than 0.1K up to 200-300°C. The "cheap" PT100 are more of the order of 
> 1-10°C
> accuracy... all numbers just using a two-point calibration.
> 
> For more information on this see [1] chapter 6 and [2] for industrial 
> sensors.
> 
> NTC sensors have a higher variablity of their parameters in production
> and are usually specified in % of temperature relative to their reference
> point, which is usually 25°C. Typical values are 0.1% to 5%. Additionally
> there is a deviation from the reference point, specified in °C, which
> is usually in the order of 0.1°C to 1°C.
> 
> The NTC sensors are less accurate than PT sensors, but offer the advantage
> of higher resistance (thus lower self-heating), higher slope (thus better
> precision). Biggest disadvantage is their non-linear curve. Their price
> is also a fraction of PT sensors and due to that you can have them in
> many different forms, from the 0201 SMD resistor, to a large stainless
> steal pipe that goes into a chemical tank. NTCs are the workhorse in
> todays temperature measurement and control designs.
> 
> The next category are band-gap sensors like the AD590. Their biggest
> advantage is that their 0 point is fix at 0K (and very accurately so).
> Ie they can be used with single point calibration and achieve 1°C accuracy
> this way. Their biggest drawback their large thermal mass and large
> insulating case, because they are basically an standard, analog IC.
> Ie their main use is in devices where there is a lot of convection and
> slow temperature change. Due to their simple and and quite linear
> characteristics, they are often used in purely analog temperature
> control circuits, or where a linearization is not feasible.
> But only if price isn't an issue (they cost 10-1000 times as
> much as an PTC). Their biggest disadvantage, beside their slow
> thermal raction time, is their large noise uncorrelated to the
> supply voltage, and thus cannot be compensated by ratiometric measurement.
> They are also more suceptible to mechanical stress than NTC's and PT's,
> due to their construction. Similar to voltage references (which they
> actually are), their aging is quite substantial and cannot be neglected
> in precision application.
> With a 3 point calibration, better than 0.5°C accuracy can be achieved
> (modulo aging) within their operating temperature range, which is
> rather limited, compared to the other sensor types.
> 
> I don't know enough about thermocouples to say much about them, beside
> that they are cumbersome to work with (e.g. the cold contact) and
> produce a low voltage (several µV) output with quite high impedance,
> which makes the analog electronics difficult to design as well.
> 
> With todays electronics, the easiest sensors to work with are NTC and
> PT100/PT1000 as most high resolution delta-sigma ADCs have direct support
> for 3 and/or 4 wire measurement of those, including compensation for
> reference voltage/current variation. Using a uC as control element
> also