Thermocouple accuracy question

MtnHaul

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Well basically I'm starting to wonder if my pyro is reading accurately. The gauge reads about 10 degrees higher than ambient air temps first thing in the morning--no heated garage and probe mounted in exhaust manifold. Should inside temp of exhaust manifold be the same as ambient?

Also I turned up the fuel 1.5 flats and my EGTs didn't seem to go up much, but the truck sure does feel peppier in traffic. Just concerned about doing some damage that could be avoided.
 

Clb

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Pyro\thermocouple compatibility comes to mind, as does accurately gauging the temps.


As to fuel
Turn it up till it gets hot or doggy.
You may have some windage to play with.
 

MtnHaul

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Pyro\thermocouple compatibility comes to mind, as does accurately gauging the temps.


Both couple and gauge were purchased as combo from thesensorconnection.com

Auber Instruments digital gauge and I assume the correct probe.
 

DaveBen

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10 degrees higher won't hurt anything. What temps are you seeing now?
 

MtnHaul

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Well yesterday was the second uphill WOT test after increasing fuel and with EGTs only about 930ish I caught whiff of a new smell and immediately backed off--could have been the vehicle in front of me but it was a newer 'Yota so doubt it. The first WOT test was on the same hill and I smelled nothing odd and EGTs were in the 900s almost hitting 1000 when I crested the top in 3rd but not completely wound out. Going for some errands today and will see if third time learns me sumpin' new. I don't mind if my engine blows up, but I do mind if it's due to a stupid mistake on my part.
 

gandalf

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I'm guessing that you're doing your test runs on 17, either side of the hill. Watch for CHP. They seem to be doing more speed traps lately. Last Friday I saw 2 on hyway 9, Saratoga side of 35. That's quite unusual.

The temps you mention don't seem to be anything I'd worry about on 17. The limit should be about 1150*F.

I think a more valid test would be doing the same run, pulling a medium load. Yes, it's a more conservative test, but if your temps are good pulling a load, they're guaranteed to be good unloaded.
 

MtnHaul

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Well after a few more uphill runs, unloaded, I only managed to hit 1000-1050 in 3rd, not enough RPMs in 4th so of course temps went higher. I guess it's OK, no more smells, at least no new ones. I'm a little surprised the Facet kept up after I bumped the fuel.

I'm not running over highway 17 but there is a long uphill at 10% that runs from highway 1 up to Bonny Doon--only seen about 9 LEO vehicles in several decades of living up here.
 

Clb

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From post #1 you mention "ambient " how are you gauging this?

quick blasts
1100* is safe
1150* time to get ready to lift
1200* alum. Gets soft
sustained runs above this =oopsie
1300*
Well lets not find out
 

nelstomlinson

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Auber Instruments digital gauge and I assume the correct probe.
Digital gauge. I see your problem.

You would like to know temp to the nearest 50F or so, but it's telling you temp to the nearest 1F or so. That precision is probably bogus. With an analog gauge, you would never know if it was 10 or so degrees off at ambient, and you would be happy.

You want it to be accurate up around 900F to 1100F. If this thermocouple was calibrated for EGT use, it probably is accurate up around the range you care about. It is probably not very accurate down around ambient, but you don't care about that.
 

CDX825

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Pyrometers are calibrated to 70 degrees gauge temp if I remember right. So its actually looking at the temp difference between the gauge and the probe to come up with a reading. The isspro EV2 series pyrometers are the only ones I know that have temperature compensation and will show accurate at all temps.
 

Cubey

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Pyrometers are calibrated to 70 degrees gauge temp if I remember right. So its actually looking at the temp difference between the gauge and the probe to come up with a reading. The isspro EV2 series pyrometers are the only ones I know that have temperature compensation and will show accurate at all temps.

I wonder about the Isspro "Classic" ones. My RV has one of these, made back around 1985:

http://www.issprogauges.com/Classic-0-1500-deg-F-Pyrometer-Gauge-p/iss-r607g.htm
 

CDX825

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CDX, I'm not following what you're saying about calibrated to gauge temp?

Thermocouples work off of temperature difference to create a voltage. So its actually reading the difference between the probe and the other end of the circuit that happens to be in the gauge. They have set the gauge side to 70 degrees. So its comparing that voltage to the voltage on the probe end to come up with a reading.

Problem is that your gauge isn't always going to be at 70 degrees so Isspro decided to do something no one else has done and make the EV2 series temperature compensated. So if the gauge isn't at 70 it knows and accounts for it to give a more accurate reading.
 

MtnHaul

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Digital gauge. I see your problem.

Well, anything can break & I like the accuracy and despite what many people say I actually find the digital display easier to read at a glance than an analog model, especially given the mounting location I went with. Before installing the gauge I played around with it a bit to see how fast it reacted to temperature changes and it was very responsive, but yeah it is accuracy that isn't really needed in a pyro application on a daily diver work truck. I'm just having fun with this truck and doing some things only for the sake of doing them and learning.

I did contact The Sensor Connection and they sent me this in reply:

Thanks for your purchase. Looks like your system is coming up on about 3 years of age. After use EGT probes will sometimes experience what’s called aging. Aging causes the measurement to shift a bit, 10 degrees is not unheard of. The good news is that this does not mean the probe is going bad. This shift can be taken out in the gauge via the offset function. We’d suggest going into the gauge’s program and adding a -10 offset. Here’s a quick video demonstrating how to program in the offset.

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Nice to know an offset is an option but I'm not going to worry about it. Don't know about the "aging" but at least their suggestion wasn't to just buy another thermocouple and/or gauge.

Nice tidbit of info on Type K thermocouple calibration

https://calibrationawareness.com/thermocouple-wire-calibration-procedure-type-k-thermocouple

CDX was right about them calibrated at 70F, or 73.4F if hairs must be split:D
 

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