Innovate Motorsports LogWorks 3 - Manual (Page 34)

LogWorks3_Manual_1.01.doc - 34 -
An example of a wrong table:
0
0.5
1
1.5
2
2.5
3
-20 -10 0 10 20 30 40
Note that 2.1 V could either mean 0 PSI or 15 PSI.
Different than the custom setting in Field 6. and 7. of the Channel Configuration dialog
box, the lookup table will NOT be automatically expanded to 0..5V. Instead the
resulting log is clipped to the minimum and maximum of the table entries.
If this dialog box was started from the LogWorks main window, double-clicking
on one of the voltage fields, then right clicking on it will show a menu that allows you
to paste the current input voltage of this input.
When Clicking the Thermistor Temp Sensor button in this Dialog Box, it will show the Thermistor
calculator.
4.2 Thermistor Temp Sensor Configuration
Most IAT or CT sensors are actually NTC thermistors. So are many oil-temperature sensors.
NTC stands for negative temperature coefficient. These sensors are resistance type sensors and
their resistance changes such that it lowers with higher temperature. The resistance curve over
temperature is not linear.
Although there are many published resistance curves for commonly available IAT or CT sensors,
these tables typically show only the nominal values. Actual production sensors can vary by as
much as 20% from the nominal values. For many applications, like turbo or intercooler efficiency
calculations, multiple sensors are needed to measure pre- and post intercooler or compressor
temperatures. The wide tolerance of production sensors makes it necessary to custom calibrate
them to get reliable accuracy. If correctly calibrated, any cheap thermistor is just as accurate as a
lab-grade temperature sensor.
The thermistor calculator can produce a custom input lookup table for LogWorks.
For that it needs the resistance of the sensor at three different temperatures. The temperatures
MUST differ from each other by at least 25 degC or 45 degF.