[Gmecm] CTS and MAT lookup differences

[holdenstarfire at optusnet.com.au]

No sure if the $58 is the same as other code of the same era but maybe
this helps
Adrian

;	#########################################################
;	#							#
;	#		MAT VARIABLE  (MATDEG)			#
;	#  							#
;	#  THIS TABLE PROVIDES A VALUE THAT SIMULATES A		#
;	#  LINEARIZED MANIFOLD AIR TEMPERATURE VARIABLE FROM	#
;	#  A RAW A/D MAT READING USING A 1K PULLUP OVER THE	#
;	#  ENTIRE TEMPERATURE RANGE.				#
;	#  							#
;	#  IT IS USED IN SYSTEMS THAT HAVE BOTH COOLANT AND MAT	#
;	#  SENSORS AND NEED TEMPERATURE VARIABLES WITH COMMON	#
;	#  SCALING.  THE MATDEG VAIABLE HAS THE SAME SCALING	#
;	#  AS THE COOLDEG VARIABLE, BUT SINCE ONLY A SINGLE 	#
;	#  1K PULLUP IS USED (INSTEAD OF THE DUAL-PULLUP SCHEME	#
;	#  USED FOR COOLDEG), MATDEG CAN BE INACCURATE AT 	#
;	#  BOTH TEMPERATURE EXTREMES.				#
;	#							#
;	#  NOTE THAT SOFTWARE MUST SUBTRACT 12 FROM THE RAW	#
;	#  A/D VALUE BEFORE THE TABLE LOOKUP TO IMPROVE THE	#
;	#  ACCURACY OF MATDEG AT THE TEMPERATURE EXTREMES.	#
;	#							#
;	#########################################################
;
FP41K:
;					DEG C
	db	$FB;			148.5
	db	$CB;			112.5
	db	$B4;			95
	db	$A3;			83.5
	db	$97;			73
	db	$8C;			65
	db	$82;			57.7
	db	$79;			51
	db	$71;			44.7
	db	$69;			38.5
	db	$60;			32
	db	$57;			25.5
	db	$4D;			18
	db	$41;			8.5
	db	$30;			-4
	db	$08;			-34
	db	$00;			V-COLD
;


-----Original Message-----
From: gmecm-bounces at diy-efi.org [mailto:gmecm-bounces at diy-efi.org] On
Behalf Of Robin Handley
Sent: Sunday, 18 June 2006 3:58 AM
To: gmecm at diy-efi.org
Subject: Re: [Gmecm] CTS and MAT lookup differences

I've now compared the Sunbird ALDL MAT raw values with ones computed
from
the input resistances, (computed ones were based on the assumption of a
1k
pull-up resistor - observing that a quantity in the PROMgrammer export
is
called 'MAT1K'. The match was very good. So I now believe that the ALDL
MAT
values _are_ raw A/D values.

This is frustrating though as, in order to get my ALDL
monitoring/logging
program to show MAT in deg C, I would have to insert a lookup table in
its
code, equivalent to the one in the Sunbird code. This would be the first
occurance of this, so I'm a bit suspicious that I've got things wrong.
Can
anybody comment?

Are the A/D->deg C lookup array values in the Sunbird/$58 code scaled
using
the usual ARG = (deg C - 40) * (4/3) ?

I used this formula in reverse to calculate deg C from the Sunbird/$58
MAT
lookup array values, and referenced these to calculated resistance
values,
based on A/D steps of 16 and a 1k pull-up resistor. I then compared
these to
the values at: http://www.diy-efi.org/gmecm/component_info/sensors.html.
The
result was not a good match. Does this mean the A/D->deg C formula is
wrong,
or the assumption of uniform A/D steps of 16 down the MAT lookup table?

Robin

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