Tracy wrote:

Bottom line is, if you need very accurate readings, learn to calibrate the EM2 if that is what you are using.  To do this, you need a good reference.  The easiest way is to use a non-contact (infra-red) thermometer.  Harbor Freight and others are now selling inexpensive ones for about $10.00.  No reason for any airplane builder not to have one.   Be sure to paint the test points on the part to be measured with a spot of flat black paint to eliminate emissivity errors 

Be careful; though.  I haven’t seen one for $10; but I did go to Harbor Freight about a month ago, and bought one that was on sale for $39.95 (marked down for $59).  I wanted to double check the temps in and out of the oil cooler.  It didn’t take me long to realize it was not reading correctly.  I have a lab grade thermometer that I then checked it against.  It was off about 10 degrees or more at room temp on any surface.  At higher temps it was off by more (30 – 40 F at about 180) on any surface with emissivity less than about .9.  It was very accurate pointed at the cooler core (essentially a ‘black body’ – emissivity very close to 1.0).  I returned it for a refund.  Maybe you’ll have better luck.

I had previously borrowed one from a friend which was quite accurate, and used it to calibrate coolant and oil temps.  Air temp sensor and CHT TC channels I calibrated using ice water and hot water with the lab thermometer in it.  I used pressure gauges to calibrate MAP and fuel and water pressure.  Yes, my MAP calibration data is different than Tracy’s (I guess the pressure variation is different in FL J.)

FWIW,

Al