I own several Fluke 52 stereo thermometers with K themocouples. They run 40 μV/C°. All thermistors have tiny outputs without op amps. They also suffer from self heating. AD590 sensors give AT LEAST 15 mV/C° without op amps. If a regulated 3,000V supply is available they can give 2 V/C° into a 1 Watt 10 Meg resistor. πθ°μΩω±√·Γλ WB0KVV ---------- Forwarded message ---------- From: Bob kb8tq <kb8tq@n1k.org> Date: Sun, Jun 4, 2017 at 11:46 AM Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Cc: "rward0@aol.com" <rward0@aol.com>, "Donald E. Pauly" <trojancowboy@gmail.com> Hi I think you have thermistors and thermocouples a bit mixed up. You can get quite substantial output voltages from a thermistor bridge…. Bob > On Jun 4, 2017, at 11:44 AM, Donald E. Pauly <trojancowboy@gmail.com> 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. > > Where did you get the idea to use a 1 k load for an AD590? If you run > it from a -5 V supply you can use a 15 k load to a +5V supply. This > gives 15 V/C° output. If you drive it from a 10 Meg impedance current > source, you get 30,000 V/ C°. If I remember correctly, I drove a > power MOSFET heater gate directly in my prototype oven 20 years ago. > It would go from full off to full on in 1/15 ° C. Noise is 1/25,000 ° > C in a 1 cycle bandwidth. > > The room temperature coefficient of an AT crystal is -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 to get ±1 ppb/C°. If the > temperature can be held to ±0.001° C, this is ±1 part per trillion. > This kind of accuracy has never been heard of. Feed forward also > allows you to incorporate the components of the oscillator into the > thermal behavior. It does no good to have a perfect crystal if the > oscillator components drift. > > πθ°μΩω±√·Γλ > WB0KVV > > ---------- Forwarded message ---------- > From: jimlux <jimlux@earthlink.net> > Date: Sun, Jun 4, 2017 at 4:47 AM > Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies > To: time-nuts@febo.com > > > On 6/3/17 9:56 PM, Donald E. Pauly wrote: > >> It was only in the early 70s that Analog Devices invented the AD590 >> solid state temperature sensor. It made thermister bridges obsolete. > > > There is a difference between something like a platinum resistance > thermometer (PRT or RTD) and a thermistor, but they both are "measure > resistance to measure temperature" devices. > > Yes, the AD590 is a useful part (I've got some in a device being > launched in August), but PRTs,thermistors, and thermocouples are still > widely used. > > I don't know that the inherent precision (at room temperature)of the > various techniques is wildly different. A 1mV/K signal (AD590 into a > 1k resistor) has to be measured to 0.1mV for 0.1 degree accuracy. > That's out of 300mV, so 1 part in 3000 > > A type E thermocouple is 1.495 mV at 25C and 1.801 at 30C, so about > 0.06 mV/K slope. Measure 0.006mV for 0.1 degree (plus the "cold > junction" issue). 1 part in 250 measurement. > > Modern RTDs all are 0.00385 ohm/ohm/degree at 25C. Typically, you > have a 100 ohm device (although there are Pt1000s), so it's changing > 0.385 ohm/degree. 1 part in 3000 > > Checking the Omega catalog.. A 44007 has nominal 5k at 25C, and is > 4787 at 26C, so 1 part in 24. > > Especially these days, with computers to deal with nonlinear > calibration curves, there's an awful lot of TCs and Thermistors in > use. The big advantage of the AD590 and PRT is that they are basically > linear over a convenient temperature range. > > In a variety applications, other aspects of the measurement device are > important - ESD sensitivity, tolerance to wildly out of spec > temperature without damage, radiation effects etc. Not an issue here, > but I'll note that the thermistor, PRT, and thermocouple are > essentially ESD immune. The AD590 most certainly is not. > > If you go out and buy cheap industrial PID temperature controller it > will have input modes for various thermocouples and PRTs. I suppose > there's probably some that take 1uA/K, but it's not something I would > expect. > > So I wouldn't say thermistor bridges (or other temperature > measurements) are obsolete. > _______________________________________________ > 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.

Hi A thermistor has *no* output unless it is in a circuit that biases it up. A thermocouple is the one that has an output when no bias is present…. Take a 10K thermistor and a 10K resistor and put them in series. You will get roughly Vcc / 2 at 25C at the junction of the two parts.. The output will change about 1.5% per degree. With a 5V Vcc, that’s around 38 mV/C. Bob > On Jun 4, 2017, at 4:49 PM, Donald E. Pauly <trojancowboy@gmail.com> wrote: > > I own several Fluke 52 stereo thermometers with K themocouples. They > run 40 μV/C°. All thermistors have tiny outputs without op amps. > They also suffer from self heating. AD590 sensors give AT LEAST 15 > mV/C° without op amps. If a regulated 3,000V supply is available they > can give 2 V/C° into a 1 Watt 10 Meg resistor. > > πθ°μΩω±√·Γλ > WB0KVV > > > ---------- Forwarded message ---------- > From: Bob kb8tq <kb8tq@n1k.org> > Date: Sun, Jun 4, 2017 at 11:46 AM > Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Cc: "rward0@aol.com" <rward0@aol.com>, "Donald E. Pauly" > <trojancowboy@gmail.com> > > > Hi > > I think you have thermistors and thermocouples a bit mixed up. You can get > quite substantial output voltages from a thermistor bridge…. > > Bob > >> On Jun 4, 2017, at 11:44 AM, Donald E. Pauly <trojancowboy@gmail.com> 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. >> >> Where did you get the idea to use a 1 k load for an AD590? If you run >> it from a -5 V supply you can use a 15 k load to a +5V supply. This >> gives 15 V/C° output. If you drive it from a 10 Meg impedance current >> source, you get 30,000 V/ C°. If I remember correctly, I drove a >> power MOSFET heater gate directly in my prototype oven 20 years ago. >> It would go from full off to full on in 1/15 ° C. Noise is 1/25,000 ° >> C in a 1 cycle bandwidth. >> >> The room temperature coefficient of an AT crystal is -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 to get ±1 ppb/C°. If the >> temperature can be held to ±0.001° C, this is ±1 part per trillion. >> This kind of accuracy has never been heard of. Feed forward also >> allows you to incorporate the components of the oscillator into the >> thermal behavior. It does no good to have a perfect crystal if the >> oscillator components drift. >> >> πθ°μΩω±√·Γλ >> WB0KVV >> >> ---------- Forwarded message ---------- >> From: jimlux <jimlux@earthlink.net> >> Date: Sun, Jun 4, 2017 at 4:47 AM >> Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies >> To: time-nuts@febo.com >> >> >> On 6/3/17 9:56 PM, Donald E. Pauly wrote: >> >>> It was only in the early 70s that Analog Devices invented the AD590 >>> solid state temperature sensor. It made thermister bridges obsolete. >> >> >> There is a difference between something like a platinum resistance >> thermometer (PRT or RTD) and a thermistor, but they both are "measure >> resistance to measure temperature" devices. >> >> Yes, the AD590 is a useful part (I've got some in a device being >> launched in August), but PRTs,thermistors, and thermocouples are still >> widely used. >> >> I don't know that the inherent precision (at room temperature)of the >> various techniques is wildly different. A 1mV/K signal (AD590 into a >> 1k resistor) has to be measured to 0.1mV for 0.1 degree accuracy. >> That's out of 300mV, so 1 part in 3000 >> >> A type E thermocouple is 1.495 mV at 25C and 1.801 at 30C, so about >> 0.06 mV/K slope. Measure 0.006mV for 0.1 degree (plus the "cold >> junction" issue). 1 part in 250 measurement. >> >> Modern RTDs all are 0.00385 ohm/ohm/degree at 25C. Typically, you >> have a 100 ohm device (although there are Pt1000s), so it's changing >> 0.385 ohm/degree. 1 part in 3000 >> >> Checking the Omega catalog.. A 44007 has nominal 5k at 25C, and is >> 4787 at 26C, so 1 part in 24. >> >> Especially these days, with computers to deal with nonlinear >> calibration curves, there's an awful lot of TCs and Thermistors in >> use. The big advantage of the AD590 and PRT is that they are basically >> linear over a convenient temperature range. >> >> In a variety applications, other aspects of the measurement device are >> important - ESD sensitivity, tolerance to wildly out of spec >> temperature without damage, radiation effects etc. Not an issue here, >> but I'll note that the thermistor, PRT, and thermocouple are >> essentially ESD immune. The AD590 most certainly is not. >> >> If you go out and buy cheap industrial PID temperature controller it >> will have input modes for various thermocouples and PRTs. I suppose >> there's probably some that take 1uA/K, but it's not something I would >> expect. >> >> So I wouldn't say thermistor bridges (or other temperature >> measurements) are obsolete. >> _______________________________________________ >> 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. > _______________________________________________ > 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.

On 6/4/17 1:49 PM, Donald E. Pauly wrote: > I own several Fluke 52 stereo thermometers with K themocouples. They > run 40 μV/C°. All thermistors have tiny outputs without op amps. > They also suffer from self heating. AD590 sensors give AT LEAST 15 > mV/C° without op amps. If a regulated 3,000V supply is available they > can give 2 V/C° into a 1 Watt 10 Meg resistor. > 3kV? That's an interesting concept. Better make sure you set your resistors up right and keep your temperature range limited, since the max voltage across the device is 30V. And the power supply ripple had better be less than 1V (PSRR is 0.1 uA/V at 15V, and 0.5 uA/V at 5V). What's the tempco of that resistor? And, you know that the calibration error is +/- 0.5 degree (for the better M grade).. Yeah, it's repeatable to 0.1 degree (0.1 uA).