Post by thread:[EE] Fast temp sensor?

I'm searching for a fast temp sensor for measuring ambient air temperature (with some overhead) -- say -10deg-C to 120deg-C. 1% accuracy or better. There are a lot of sensors that meet this numerical criteria, but what types of temps sensors are *fast*? I usually don't see response time listed in the datasheets (and not even sure what the parameter is for response time), and I don't have a specific value for how fast it should be, but I want to compare various sensor types and start investigating/experimenting with the fastest of these. I did find "fast response RTD's" and wondering how they compare (speed-wise) to other alternatives such as semiconductor sensors. I expect the plastic housings for TO-92 types and similar would be enough of an insulator to significantly increase the response time. Will the metal can versions (TO-39 IIRC) be considerably faster? Open element sensors and low-mass sensors should be fast. But I'm sure I am missing a lot of other possibilities here. Any links/clues on this? Thanks, -Neil. -- View this message in context: www.nabble.com/Fast-temp-sensor--tp18104658p18104658.html Sent from the PIC - [EE] mailing list archive at Nabble.com.

Hi Neil, I've been impressed by the response speed of tiny thermocouples. Their response is on the order of a second. I'd say that it is on the order of 20 seconds for typical semiconductor temp sensors. RTDs are probably in the same range as thermocouples but tend to be more expensive I think. I have seen to-92 packaged temp sensors from National which list thermal response time in their graphs section. The response is roughly exponential, like an RC circuit with a step input, so the graph should give you the time constant (at which time the temp difference is reduced to 37% of the original difference). You could also possibly greatly increase the response speed of any temp sensor by mounting it to a small heatsink and blowing air over it with a small fan. Sean On Wed, Jun 25, 2008 at 12:13 AM, PicDude <spam_OUTpicdude2TakeThisOuTavn-tech.com> wrote: {Quote hidden}> > I'm searching for a fast temp sensor for measuring ambient air temperature > (with some overhead) -- say -10deg-C to 120deg-C. 1% accuracy or better. > > There are a lot of sensors that meet this numerical criteria, but what types > of temps sensors are *fast*? I usually don't see response time listed in > the datasheets (and not even sure what the parameter is for response time), > and I don't have a specific value for how fast it should be, but I want to > compare various sensor types and start investigating/experimenting with the > fastest of these. > > I did find "fast response RTD's" and wondering how they compare (speed-wise) > to other alternatives such as semiconductor sensors. I expect the plastic > housings for TO-92 types and similar would be enough of an insulator to > significantly increase the response time. Will the metal can versions > (TO-39 IIRC) be considerably faster? Open element sensors and low-mass > sensors should be fast. But I'm sure I am missing a lot of other > possibilities here. > > Any links/clues on this? > > Thanks, > -Neil. > > -- > View this message in context: www.nabble.com/Fast-temp-sensor--tp18104658p18104658.html > Sent from the PIC - [EE] mailing list archive at Nabble.com. > > -

The reason why you'll don't find fast and accurate temperature sensors is because the temperature variation is slowly by definition (faster in air speed and slower in liquid). The speed of the analogic temperature sensors is gaven by the size of the sensor. A thermocouple without case or a thin film RTD is faster than a thermocouple with case or a huge 5mm diameter RTD. You can find at Omega some small and cheap RTD which could met your 1% request. But from the sensor accuracy to the final measuring value accuraccy it's a long way. Vasile On 6/25/08, PicDude <picdude2KILLspamavn-tech.com> wrote: {Quote hidden}> > I'm searching for a fast temp sensor for measuring ambient air temperature > (with some overhead) -- say -10deg-C to 120deg-C. 1% accuracy or better. > > There are a lot of sensors that meet this numerical criteria, but what types > of temps sensors are *fast*? I usually don't see response time listed in > the datasheets (and not even sure what the parameter is for response time), > and I don't have a specific value for how fast it should be, but I want to > compare various sensor types and start investigating/experimenting with the > fastest of these. > > I did find "fast response RTD's" and wondering how they compare (speed-wise) > to other alternatives such as semiconductor sensors. I expect the plastic > housings for TO-92 types and similar would be enough of an insulator to > significantly increase the response time. Will the metal can versions > (TO-39 IIRC) be considerably faster? Open element sensors and low-mass > sensors should be fast. But I'm sure I am missing a lot of other > possibilities here. > > Any links/clues on this? > > Thanks, > -Neil. > > -- > View this message in context: www.nabble.com/Fast-temp-sensor--tp18104658p18104658.html > Sent from the PIC - [EE] mailing list archive at Nabble.com. > > -

I'm doing a lot of work with thermistors these days....my current prototype is <0.1c accuracy and 0.1c resolution on the digital side. This is from a $4 thermistor encased in copper. You'll actually find "standing air" response times published by most thermistor manufacturers -- as long as it's a thermistor truly meant for instrumentation. In my experience, they're in the order of 25s in standing air. Moving air, stirred oil, and water figures are sometimes supplied and will all be faster. Not sure if that really helps, my my 2 cents Canadian ;) -marc On Wed, Jun 25, 2008 at 12:13 AM, PicDude <.....picdude2KILLspam.....avn-tech.com> wrote: {Quote hidden}> > I'm searching for a fast temp sensor for measuring ambient air temperature > (with some overhead) -- say -10deg-C to 120deg-C. 1% accuracy or better. > > There are a lot of sensors that meet this numerical criteria, but what > types > of temps sensors are *fast*? I usually don't see response time listed in > the datasheets (and not even sure what the parameter is for response time), > and I don't have a specific value for how fast it should be, but I want to > compare various sensor types and start investigating/experimenting with the > fastest of these. > > I did find "fast response RTD's" and wondering how they compare > (speed-wise) > to other alternatives such as semiconductor sensors. I expect the plastic > housings for TO-92 types and similar would be enough of an insulator to > significantly increase the response time. Will the metal can versions > (TO-39 IIRC) be considerably faster? Open element sensors and low-mass > sensors should be fast. But I'm sure I am missing a lot of other > possibilities here. > > Any links/clues on this? > > Thanks, > -Neil. > > -- > View this message in context: > www.nabble.com/Fast-temp-sensor--tp18104658p18104658.html > Sent from the PIC - [EE] mailing list archive at Nabble.com. > > -

Quoting Marc Nicholas <EraseMEgeekythingspam_OUTTakeThisOuTgmail.com>: Seems to me that you really should start with a specification (or some idea of what you require) and go from there. I have used thermocouples (open wire wire and open ribbon) for really fast response with air (for example, to control a proportional valve for a combustion heated air flow). But to get 0.1°C *accuracy* is probably optimistic unless it's laboratory conditions. 0.1°C short term stability shouldn't be a problem with good instrumentation and controls. {Quote hidden}> I'm doing a lot of work with thermistors these days....my current prototype > is <0.1c accuracy and 0.1c resolution on the digital side. This is from a $4 > thermistor encased in copper. > > You'll actually find "standing air" response times published by most > thermistor manufacturers -- as long as it's a thermistor truly meant for > instrumentation. In my experience, they're in the order of 25s in standing > air. Moving air, stirred oil, and water figures are sometimes supplied and > will all be faster. > > Not sure if that really helps, my my 2 cents Canadian ;) > > -marc > > On Wed, Jun 25, 2008 at 12:13 AM, PicDude <picdude2spam_OUTavn-tech.com> wrote: > >> >> I'm searching for a fast temp sensor for measuring ambient air temperature >> (with some overhead) -- say -10deg-C to 120deg-C. 1% accuracy or better. >> >> There are a lot of sensors that meet this numerical criteria, but what >> types >> of temps sensors are *fast*? I usually don't see response time listed in >> the datasheets (and not even sure what the parameter is for response time), >> and I don't have a specific value for how fast it should be, but I want to >> compare various sensor types and start investigating/experimenting with the >> fastest of these. >> >> I did find "fast response RTD's" and wondering how they compare >> (speed-wise) >> to other alternatives such as semiconductor sensors. I expect the plastic >> housings for TO-92 types and similar would be enough of an insulator to >> significantly increase the response time. Will the metal can versions >> (TO-39 IIRC) be considerably faster? Open element sensors and low-mass >> sensors should be fast. But I'm sure I am missing a lot of other >> possibilities here. >> >> Any links/clues on this? >> >> Thanks, >> -Neil. >> >> -- >> View this message in context: >> www.nabble.com/Fast-temp-sensor--tp18104658p18104658.html >> Sent from the PIC - [EE] mailing list archive at Nabble.com. >> >> -

Hi Ariel, Yes, there would be a tradeoff. I used the term "heatsink" very loosely. I had in mind a small piece of copper tape or foil, attached to one of the leads of the part. This way, you enhance the thermal conductivity from the air directly in to the die of the sensor. I have not done tests here - it could well be that a bare sensor would be faster. Sean On Wed, Jun 25, 2008 at 9:17 AM, Ariel Rocholl <KILLspamarochollKILLspamgmail.com> wrote: {Quote hidden}> 2008/6/25 Sean Breheny <RemoveMEshb7TakeThisOuTcornell.edu>: >> >> You could also possibly greatly increase the response speed of any >> temp sensor by mounting it to a small heatsink and blowing air over it >> with a small fan. > > Intuition tells me there is probably a difficult tradeoff to balance > between adding lot of "temperature inertia" to the device with a > heatsink and how to compensate it by additional airflow. I wouldn't > add any heatsink to get faster response time. > > -- > Ariel Rocholl > Madrid, Spain > -

Quoting Ariel Rocholl <TakeThisOuTarochollEraseMEspam_OUTgmail.com>: > 2008/6/25 Sean Breheny <RemoveMEshb7TakeThisOuTcornell.edu>: >> >> You could also possibly greatly increase the response speed of any >> temp sensor by mounting it to a small heatsink and blowing air over it >> with a small fan. > > Intuition tells me there is probably a difficult tradeoff to balance > between adding lot of "temperature inertia" to the device with a > heatsink and how to compensate it by additional airflow. I wouldn't > add any heatsink to get faster response time. Just because a tradeoff is difficult to evaluate doesn't mean you shouldn't try to do it. ;-) If the heatsink did not impede flow to the sensor, then anything you attached thermally to it that responds faster than the sensor itself should speed things up because heat will flow from the faster bits to/from the slower bits. Assuming a large amount of air flow etc. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" s...EraseME.....interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com

PicDude wrote: {Quote hidden}> I'm searching for a fast temp sensor for measuring ambient air temperature > (with some overhead) -- say -10deg-C to 120deg-C. 1% accuracy or better. > > There are a lot of sensors that meet this numerical criteria, but what types > of temps sensors are *fast*? I usually don't see response time listed in > the datasheets (and not even sure what the parameter is for response time), > and I don't have a specific value for how fast it should be, but I want to > compare various sensor types and start investigating/experimenting with the > fastest of these. > > I did find "fast response RTD's" and wondering how they compare (speed-wise) > to other alternatives such as semiconductor sensors. I expect the plastic > housings for TO-92 types and similar would be enough of an insulator to > significantly increase the response time. Will the metal can versions > (TO-39 IIRC) be considerably faster? Open element sensors and low-mass > sensors should be fast. But I'm sure I am missing a lot of other > possibilities here. > > Any links/clues on this? > > Thanks, > -Neil. > Find something in a very small package and then use more than one to achieve high statistical accuracy. i.e. n samples with 1 degree accuracy would give you 1/sqrt(n) accuracy IIRC. You could possibly do a derivative calculation to achieve quicker estimates of the ending reading i.e: You read 105 degrees. The dT/dt is -4 degrees. You might predict that the future sample is likely to be closer to 101 degrees or that the ACTUAL temperature is lower than 105 because you can account for your sensor's thermal mass. "YMMV" - Martin

Lots learned a lot over the past few days, and it really does seem that thermocouples (especially open-elements) are very very fast. Type T thermocouples are apparently the most accurate and available in two classes, with 0.5 deg-C error versions commonly available. But thermocouples need a lot (relatively) of support circuitry, especially since this is in an automotive application (measuring air temp at a couple points in the intake tract). 1sec to 2sec works fine, since this is a monitoring application, and 1% error would be nice, although a bit more would still be acceptable. Mounting (for the end-user) will be a major factor as well, so any basic element/component that needs to be PCB-mounted becomes less desirable, as I'd have to factor in the labor cost to build those to a user-friendly format ... and that's still be decided upon. I had missed the graphs with response time in those datasheets (LM35 etc) -- I was looking for electrical parameters. But checking back now, they're relatively quite slow. I found RTD's that are available in better than 1 sec response time using open elements, and they require minimal support circuitry. They also come mounted to a stem/flange/etc so end-user install is ready-to go. The problem is cost -- so far they're in the $35-$40 price range each (in 50-100pc quantities). I always thought that thermistors were not-so-accurate, but I've been corrected again it seems. I'm looking at various datasheets now in the 0.5% to 1% range, and they seem promising. Very low cost (<$1 ), and I'm working out a mounting structure to see just how much it would cost if assembled in-house. I also found some suppliers of thermistors in flanged probes, so I have some calls to make this week. Thanks, -Neil. -- View this message in context: www.nabble.com/Fast-temp-sensor--tp18104658p18181248.html Sent from the PIC - [EE] mailing list archive at Nabble.com.

At 10:14 AM 6/29/2008, you wrote: >Lots learned a lot over the past few days, and it really does seem that >thermocouples (especially open-elements) are very very fast. Type T >thermocouples are apparently the most accurate and available in two classes, >with 0.5 deg-C error versions commonly available. But thermocouples need a >lot (relatively) of support circuitry, The cold-junction compensation also adds an error term that could be a problem in applications where the ambient varies widely (such as automotive). It adds an error that is approximately 1:1 (eg. a 1 degree error in the secondary sensor causes approximately a 1 degree error in the reading. For this reason, T/Cs are better suited for EGT than intake. ;-) > especially since this is in an >automotive application (measuring air temp at a couple points in the intake >tract). 1sec to 2sec works fine, since this is a monitoring application, Hmm.. what would cause the air temperature to change so quickly? Could you use a milled out PCB as a combination mounting method, electrical connection and heatsink? Maybe they you could use a thermistor or SMT semiconductor sensor. Monitoring is a *lot* easier than control. In control of air temperature the sensor adds a pole to the response that can cause overshoot/undershoot of the actual (not the measured) air temperature unless you grossly detune the controller to make the response sluggish. In cases where there is an object being heated or cooled that responds faster than the sensor you can get serious problems if the actual air temperature does that. {Quote hidden}>and 1% error would be nice, although a bit more would still be acceptable. > >Mounting (for the end-user) will be a major factor as well, so any basic >element/component that needs to be PCB-mounted becomes less desirable, as >I'd have to factor in the labor cost to build those to a user-friendly >format ... and that's still be decided upon. > >I had missed the graphs with response time in those datasheets (LM35 etc) -- >I was looking for electrical parameters. But checking back now, they're >relatively quite slow. I found RTD's that are available in better than 1 >sec response time using open elements, and they require minimal support >circuitry. They also come mounted to a stem/flange/etc so end-user install >is ready-to go. The problem is cost -- so far they're in the $35-$40 price >range each (in 50-100pc quantities). > >I always thought that thermistors were not-so-accurate, but I've been >corrected again it seems. They can be okay (sometimes very good), but not so trustworthy at higher temperatures. If your maximum is going to be 40 or 50°C, that's much less of a worry. > I'm looking at various datasheets now in the 0.5% >to 1% range, and they seem promising. Very low cost (<$1 ), 1% of a thermistor is a lot fewer degrees than 1% of a substantially linear sensor such as a thermocouple or RTD. Thermistors are extremely nonlinear, so they're more appropriately used over a relatively narrow temperature range. Watch that there is also a tolerance on the beta. The tolerance is kind of a conical tunnel that is narrowest at the reference temperature (eg. 25°C) and quite a bit wider at both ends. {Quote hidden}> and I'm working >out a mounting structure to see just how much it would cost if assembled >in-house. I also found some suppliers of thermistors in flanged probes, so >I have some calls to make this week. > >Thanks, >-Neil. > > > >-- >View this message in context: >www.nabble.com/Fast-temp-sensor--tp18104658p18181248.html >Sent from the PIC - [EE] mailing list archive at Nabble.com. >

Are you suggesting that cold-junction compensation is a problem in the automotive environment even with compensation? For EGT probes, I have the junction inside a sealed enclosure (so the probe cannot be removed), and the temp compensation is done in there. But because of that, plus amps, etc, I'm leaning away from that currently. I don't mind non-linear outputs, as long as they're repeatable -- I can always use tables. The temp after a turbo can change quite quickly, but I'm going on specs from the customer. > Monitoring is a *lot* easier than control. And don't forget control has a lot more liability associated with it. I used to use the DS18B20 (8-soic or 8-ttsop) and I had it on a small 1/32" thick PCB with a hole right under the chip, but it was time-intensive to solder the wires etc to the small PCB. Currently I'm working on custom-making a sensor probe using a small bead-type thermistor (see 615-1001-ND at digikey as an example), and it would be mounted in a tube with the bead mostly protruding out the end. The tube would be filled with some type of epoxy and the other end would have a couple wires on it. I'd need to solder/weld a flange onto the tube, but it would be sooo much easier if I could find a small-diameter tube (say 0.1" to 0.125" ID) that's threaded on the outside. That way, two nuts on the outside would be used to secure it. That's what I'm searching for currently. Cheers, -Neil. Spehro Pefhany wrote: {Quote hidden}> > At 10:14 AM 6/29/2008, you wrote: > > The cold-junction compensation also adds an error term that could be > a problem in applications where the ambient varies widely (such as > automotive). It adds an error that is approximately 1:1 (eg. a 1 degree > error in the secondary sensor causes approximately a 1 degree error in the > reading. For this reason, T/Cs are better suited for EGT than intake. ;-) > >> especially since this is in an >>automotive application (measuring air temp at a couple points in the intake {Quote hidden}>>tract). 1sec to 2sec works fine, since this is a monitoring application, > > Hmm.. what would cause the air temperature to change so quickly? Could > you use a milled out PCB as a combination mounting method, electrical > connection and heatsink? Maybe they you could use a thermistor or SMT > semiconductor sensor. > > Monitoring is a *lot* easier than control. In control of air temperature > the sensor adds a pole to the response that can cause overshoot/undershoot > of the actual (not the measured) air temperature unless you grossly detune > the controller to make the response sluggish. In cases where there > is an object being heated or cooled that responds faster than the sensor > you can get serious problems if the actual air temperature does that. > >>and 1% error would be nice, although a bit more would still be acceptable. >> >>Mounting (for the end-user) will be a major factor as well, so any basic >>element/component that needs to be PCB-mounted becomes less desirable, as >>I'd have to factor in the labor cost to build those to a user-friendly >>format ... and that's still be decided upon. >> >>I had missed the graphs with response time in those datasheets (LM35 etc) -- >>I was looking for electrical parameters. But checking back now, they're >>relatively quite slow. I found RTD's that are available in better than 1 >>sec response time using open elements, and they require minimal support >>circuitry. They also come mounted to a stem/flange/etc so end-user install >>is ready-to go. The problem is cost -- so far they're in the $35-$40 price {Quote hidden}>>range each (in 50-100pc quantities). >> >>I always thought that thermistors were not-so-accurate, but I've been >>corrected again it seems. > > They can be okay (sometimes very good), but not so trustworthy at higher > temperatures. If your maximum is going to be 40 or 50Â°C, that's much less > of a worry. > >> I'm looking at various datasheets now in the 0.5% >>to 1% range, and they seem promising. Very low cost (<$1 ), > > 1% of a thermistor is a lot fewer degrees than 1% of a substantially > linear > sensor such as a thermocouple or RTD. Thermistors are extremely nonlinear, > so they're more appropriately used over a relatively narrow temperature > range. > Watch that there is also a tolerance on the beta. The tolerance is kind > of a > conical tunnel that is narrowest at the reference temperature (eg. 25Â°C) > and > quite a bit wider at both ends. > > >> and I'm working >>out a mounting structure to see just how much it would cost if assembled >>in-house. I also found some suppliers of thermistors in flanged probes, so {Quote hidden}>>I have some calls to make this week. >> >>Thanks, >>-Neil. >> >> >> >>-- >>View this message in context: >>www.nabble.com/Fast-temp-sensor--tp18104658p18181248.html >>Sent from the PIC - [EE] mailing list archive at Nabble.com. >> >>

At 12:48 AM 6/30/2008, you wrote: No CRLFs. >Are you suggesting that cold-junction compensation is a problem in >the automotive environment even with compensation? Yes, the accuracy of the compensation. With a T/C system you really have two temperature sensors, and a low level amplifier, and in general the errors of all three can add. If you don't need T/C characteristics (ruggedness, wide range, maybe fast response), you're far better off to just use the CJC sensor as your thermometer and forget the T/C entirely! >For EGT probes, I have the junction inside a sealed enclosure (so >the probe cannot be removed), and the temp compensation is done in >there. But because of that, plus amps, etc, I'm leaning away from >that currently. I don't mind non-linear outputs, as long as they're >repeatable -- I can always use tables. The problem isn't the difficulty of digital linearization--that's generally a triviality-- it's loss of resolution. You might have a 100:1 range in resistance for -20C to 100 C range. Even if it's repeatable, you will have problems trying to use even a 12-bit ADC to get 0.1C resolution even though there are only 1200 0.1 C steps between -20 and 100. With a straightforward measurement of resistance you'd need more like 16 bits or some kind of range switching or linearization circuitry *ahead* of the ADC. {Quote hidden}>The temp after a turbo can change quite quickly, but I'm going on >specs from the customer. > Monitoring is a *lot* easier than >control. And don't forget control has a lot more liability >associated with it. I used to use the DS18B20 (8-soic or 8-ttsop) >and I had it on a small 1/32" thick PCB with a hole right under the >chip, but it was time-intensive to solder the wires etc to the small >PCB. Currently I'm working on custom-making a sensor probe using a >small bead-type thermistor (see 615-1001-ND at digikey as an >example), and it would be mounted in a tube with the bead mostly >protruding out the end. The tube would be filled with some type of >epoxy and the other end would have a couple wires on it. I'd need >to solder/weld a flange onto the tube, but it would be sooo much >easier if I could find a small-diameter tube (say 0.1" to 0.125" ID) >that's threaded on the outside. That way, two nuts on the outside >would be used to secure it. That's what I'm searching for >currently. Cheers, -Neil. You have something against compression fittings? Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" RemoveMEspeffspam_OUTKILLspaminterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com

On Sun, Jun 29, 2008 at 7:14 AM, PicDude <RemoveMEpicdude2TakeThisOuTspamavn-tech.com> wrote: > > Lots learned a lot over the past few days, and it really does seem that > thermocouples (especially open-elements) are very very fast. Type T > thermocouples are apparently the most accurate and available in two classes, > with 0.5 deg-C error versions commonly available. But thermocouples need a > lot (relatively) of support circuitry, especially since this is in an > automotive application (measuring air temp at a couple points in the intake > tract). 1sec to 2sec works fine, since this is a monitoring application, > and 1% error would be nice, although a bit more would still be acceptable. Hmm... GM has IAT (intake air temp) sensors. I'm not sure if they are fast enough for you. But, they have the advantage of being built to live in an automotive environment. GM parts Direct: http://www.gmpartsdirect.com/ GM IAT Sensor : 25036751 Pig Tail : 12102620 It has been a while since I've been digging around in GM ECM stuff, but I believe the temp monitoring was in the outer loops (every second).

Ford also. I think typically nearly all vehicles stating 1996, which was the main launch of OBDII have them. Possibly pick one that you can buy the connector matching. The shop manuals (at least the Ford) have troubleshooting that includes the pinouts and power and signal values expected. There are all sorts of sensors available in the auto area including absolute barometric pressure, various pressures and vacuums, float switches, etc. Select one from a common model, will be easy to duplicate if needed. From the aviation area, high temperature thermocouples that respond quickly are used for exhaust temperature on piston engines. It's common to have one thermocouple in each exhaust stack, makes it easy to diagnose a fouled sparkplug ,clogged fuel injector nozzle, or broken exhaust valve! Alex Harford wrote: {Quote hidden}> On Sun, Jun 29, 2008 at 7:14 AM, PicDude <EraseMEpicdude2spamspamBeGoneavn-tech.com> wrote: > >> Lots learned a lot over the past few days, and it really does seem that >> thermocouples (especially open-elements) are very very fast. Type T >> thermocouples are apparently the most accurate and available in two classes, >> with 0.5 deg-C error versions commonly available. But thermocouples need a >> lot (relatively) of support circuitry, especially since this is in an >> automotive application (measuring air temp at a couple points in the intake >> tract). 1sec to 2sec works fine, since this is a monitoring application, >> and 1% error would be nice, although a bit more would still be acceptable. >> > > Hmm... GM has IAT (intake air temp) sensors. I'm not sure if they are > fast enough for you. But, they have the advantage of being built to > live in an automotive environment. > > GM parts Direct: http://www.gmpartsdirect.com/ > GM IAT Sensor : 25036751 > Pig Tail : 12102620 > > It has been a while since I've been digging around in GM ECM stuff, > but I believe the temp monitoring was in the outer loops (every > second). >

Yes, but there's no way this would meet the accuracy spec. SMP's catalog shows accuracies of some OEM sensor in the 30% range (yes, 70% error!), and I can't remember anything over 80% accuracy. These are the guys that supply to the OEM's. And ECU's don't really need to know the actual temp, they just put in fuel & timing compensation factors in a table at *that* temp, whatever *that* temp may be. This is why OBD-type gauges for temps & pressures are useless. (But they're great for things like injector duty-cycles, etc, and manifold/baro pressure is generally fairly accurate). Alex Harford wrote: {Quote hidden}> > Hmm... GM has IAT (intake air temp) sensors. I'm not sure if they are > fast enough for you. But, they have the advantage of being built to > live in an automotive environment. > > GM parts Direct: http://www.gmpartsdirect.com/ > GM IAT Sensor : 25036751 > Pig Tail : 12102620 > > It has been a while since I've been digging around in GM ECM stuff, > but I believe the temp monitoring was in the outer loops (every > second). > --