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EGT Calibration

Geico266

Geico266

Well Known Member
Any ideas on how to calibrate the EGT's? I've searched, but could find nothing.

Is there an inexpesive way to calibrate them on the ground? I was thinking of an electric gizmo that you could plug in and set a range of say 1,000F through 1,500F.

I'm sure I'm not the first one to want to calibrate the guages. The only thing I can think of is to buy a stand alone EGT guage for about $100 and go flying to see if the others are in line or close to the others.
 
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n714b said:
Larry, contact me off line. You have my email address. Still the same.

Bob
Click to expand...
Sorry Robert, I don't have your e-mail address anymore. Send it to me again via PM.

Good to hear from you!
 
Okay, since no one has a way to calibrate EGT's I'm gonna invent one.

My situation is I have a BMA EFIS1. I want to verify & calibrate the EGT readings. Since the BMA is digital, and the thermocouple feed is anolog, it needs to be converted to a readable "scale" for display. There are standard scales, but when I apply them to the unit the EGT's are all over the place leading me to believe something isn't right with the EFIS1. Hense, my obsession for calibration. The veriation could be many things, wire size, connectors, ect., so I'm not blaming BMA, I just want accurate verified EGT readings.

I'm gonna take a new EGT guage and thermocouple, a 18" x 1 1/2" water pipe (thicker wall to hold heat steady), drill two holes in the pipe and insert one t-couple from the plane and the test t-couple. Tips as close as possible. A propane tourch in the pipe will be the controllable heat source. I'll tune the tourch to 500F, 700F, 900F, ect. take a reading from the EFIS on using 200F increments to build a scale.

Any comments?

Yes, I have insurance. lol
 
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Suggestion

Geico,
IF you are going to do it that way, I would fill the pipe with sand.
The sand would act as a heat transfer medium as well as help to even out the temperatures between the thermocouples. The heat capacity of the pipe and sand in combination would keep the temperature from changing too fast.
 
MarkDews said:
Geico,
IF you are going to do it that way, I would fill the pipe with sand.
The sand would act as a heat transfer medium as well as help to even out the temperatures between the thermocouples. The heat capacity of the pipe and sand in combination would keep the temperature from changing too fast.
Click to expand...

I see your point, I was hoping to use the propane tourch and regulate the temp that way. Leave it on and adjust the flame. I'll post the results in a few weeks. It's too cold here now to work on the plane. Brr!
 
thermocouple simulator

your question intrigued me, as a decade or so ago i did some design work using platinum rtd's (resistance-thermal-devices), and had an "rtd simulator", which was basically an r-box to simulate the various temperatures. as i recall, the rtd-simulator had a national bureau of standards calibration sticker.

so, i did a web search and came up with the following product that would do what you are trying to accomplish. it's a bit pricey at $400, so maybe not an individual item. could you get enough interest in your eaa chapter to purchase one for chapter use? i dunno.....

http://www.omega.com/ppt/pptsc.asp?ref=CL540_CL540Z&Nav=temk10

the first one that pops up is $500, but since most egt probes are type "k", you could buy one of the lesser models to do "k" only (shown if you scroll down.) there may be other products out there that will do the job for less -- these simulators have way more precision than you need (0.5 oC accuracy above 600 oC).

hope you take this as a "thought-starter" post.
 
Geico266 said:
Any ideas on how to calibrate the EGT's? I've searched, but could find nothing.

Is there an inexpesive way to calibrate them on the ground? I was thinking of an electric gizmo that you could plug in and set a range of say 1,000F through 1,500F.

I'm sure I'm not the first one to want to calibrate the guages. The only thing I can think of is to buy a stand alone EGT guage for about $100 and go flying to see if the others are in line or close to the others.
Click to expand...
I don't believe that absolute accuracy is important to the function they provide as long as they each read closely to one another in the same temperature field. The thermoelectric effect is a metal couple property that is quite consistent from one TC junction to the next.
Your meter might need calibration but the TC's probably don't. You could check the accuracy and precision of the group by placing them in boiling water or an ice bath (relatively known temperatures).

-mike
 
Mike is correct in that EGTs are a "relative" measurement. Where the probes are placed in the exhaust pipes will alter the readings. When probes are placed closer to the cylinder head, they will react faster but will burn out quicker. The important thing is that all probes are the same distance from the flange and that they are calibrated with relation to each other. The actual temperature is not critical.
 
You're flying already? Or engine running? Are you already using a IRed handheld pyrometer from Graingers? For initial temps?


Someone just posted a spreedsheet for Ohms/ temp for probes on the yahoo SocalRVlist for a guy having temp issues. Not sure how that would help you.

BMA EFIS one == Love / hate relationship!!!
 
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