MSefi.com read only forum (Jan.15,2018)

I am having problems getting temperatures to read correctly within Megatune.

I installed the original 2490 ohms resistors at r4 and r7 in megasquirt.

Here are the resistance and temperatures that I recorded on the vehicle between pin 20 and ground.


Temp F Ohms resistance IAT
117 777
94 1143
91 1264
87 1302
79 1431
68 1715
65 1772
64 1809


Temp F Ohms resistance Coolant resistance measured at ms pin 21 and gnd

143 360
141 380
93 952
86 964
76 1360
68 1475
64 1549

In the Easytherm generated inc files what do these figures represent?

MATFACTOR:
; ADC Temp, degF
DB 100T ; 0 Sensor Failure - 100% applied
DB 42T ; 1 1.95
DB 81T ; 2 40.85
DB 104T ; 3 63.78
DB 120T ; 4 79.67

Help!!!!!

Cheers,

Jeff

OK,

Got it, took some time but with a little reverse calculating and with good temp/resistance pairs one can use easy therm to figure out the best match of bias resistor to be used.

Cheers,

Jag

Jag wrote:OK,

Got it, took some time but with a little reverse calculating and with good temp/resistance pairs one can use easy therm to figure out the best match of bias resistor to be used.

Cheers,

Jag

Can you share that calculating formula with the rest of us?

Pick one roughly equal to the resistance of the sensor at its midrange temperature. This is not horribly critical, so just pick the closest commonly available resistor. To see the effects of bias resistor selection, run EasyTherm to generate new .inc tables, and compare them with a text editor.

Roger.

renns wrote:Pick one roughly equal to the resistance of the sensor at its midrange temperature. This is not horribly critical, so just pick the closest commonly available resistor. To see the effects of bias resistor selection, run EasyTherm to generate new .inc tables, and compare them with a text editor.

Roger.

Ok thanks! But midrange? For working temperature in my engine or midrange of what the sensor can mesure?

Ok thanks! But midrange? For working temperature in my engine or midrange of what the sensor can mesure?

Midrange of engine temperature. Typically about 70F/20C is fine for both air and coolant.

Roger