Tracy/Joe,<= /p>

One point of clarification on my calibration methods. I used ice to check/calibrate my = thermocouples, not the sensors.

Mark

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Wednesday, October = 26, 2005 10:04 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = EM2 Calibration

Hi = Joe,

Something not = right here. The scale factor should not be negative. The default = value for oil pressure channel as shipped is +9.349. Making the EM2 user calibratable so that a variety of sensors can be used is obviously = a mixed blessing and there is a limit on just how far from the default = sensor you can go. Are you using the recommended sensor or something = else? Try to stay with the 10 - 180 ohm (low to high) VDO pressure sensor = family. Trying to calibrate with an inverse sensor (low pressure =3D high = resistance) is theoretically possible using negative scale factor but can be devilishly = tricky to do.

On temp = sensor calibration, do not use a low value (like ice water) as the low end = calibration point. Automotive gauge sensors are not linear or accurate = down there. I typically use 100 - 130 deg. F as the low end and = boiling water as the upper point. Al's suggested use of an infrared temp = gauge to calibrate is a good one.

Tracy

----- Original Message ----- =

From: Joe Hull =

To: Rotary motors in = aircraft

Sent: Wednesday, October 26, 2005 10:23 = AM

Subject: [FlyRotary] EM2 Calibration

Thanx for all the suggestions on calibrating my EM2 –

I spent 3 hours last night trying = to calibrate just the Oil Pressure sender. Only about 30 minutes of that = were real calibration tasks – the rest of the time was spent trying to get a positive number instead of a negative number. Anyone know why or how the “Scale Factor” is negative? =

If the “Scale Factor” = is negative then the derived value, of course, is negative. So, I tried to = see if I could get the scale factor to “wrap around” by bringing it = to zero – but after hours of holding buttons and countless counts to = -63.99% (and or -128) I did nothing but overflow onto the screen buffer and = start popping numbers onto screen labels. So, it was the same tedium getting = it back to where it was.

There’s got to be an easier = way!

Thanx,

Joe Hull

Redmond (Seattle), Washington

Cozy MkIV #991 (working on Engine = & Electrical & Finishing)

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