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That's what I used in my simple set-up, but it does require three wires to the sensor: Ground (could be the shield of the cable), +5 Volts and Sensor output.
I had a junction box on the engine side of the firewall which also had the EGT chips (amplified the EGT voltages to 0 to 10 Volts -- I forget the part number) and then a multi wire cable from there to my EM, with only one wire for group, +5, +10 volts and one for each signal. When removing the homemade sensors from the oil pan or engine block I would disconnect the leads from the junction box (screw terminals), roll up the wire and then screw out the sensor housing.
Finn
Wendell Voto wrote:
Tracy,
Maybe you shouldn't had said 50th but we won't tell.
Could the EM2 use LM34 temp sensors? They give 10mv/deg. F and have very good accuracy (spec is 1 degree but I get less than .1 degree repeatability one sensor to another)and track well, very linear. They are what I am using, just JB welded into a hollowed out old sensor and plan on using for oil and water temps.
Wendell
*Fine points on the EM2:*
The default sensors on the EM2 are very low cost automotive types
but they are not inherently super accurate. Usually there in no
big down-side for the water or oil temp to be off a few degrees so
most builders need not go any further. If the water temp turns
out to be actually 178 instead of 180, no big deal. Super
accuracy can be had with these sensors if you go to the trouble of
calibrating the instrument but then you must get into the nitty
gritty of the calibration procedures and the troubles can begin.
But here is where it does matter. If you are calculating thermal
loads and heat dissipation based on differential temps (let's say
water temps in and out of the radiator for instance) a few
degrees of error can make your results meaningless. In this
example, it is not uncommon for the Delta T to be in the range of
10 degrees at some power settings. If the error in temperature is
a couple of degrees, the error is huge, especially if the errors
are in opposite directions.
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. Tracy (should I have said 50th? )
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