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 = 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.
----- Original Message -----
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)
http://www.maddyhome.com/canardpages/pages/JoeHull/index.html