Innovate Motorsports LogWorks 3 - Manual (Page 11)

LogWorks3_Manual_1.01.doc - 11 -
2 Logging engine data
2.1 Data logging 101
Data logging is basically the recording of engine data. Engine data is measured with various
sensors. Two types of logging are common.
a. Time based logging
b. RPM based logging
In time based logging the sensor data is read in fixed time intervals. This is similar to how a movie
projector or a TV works. In a movie, a snapshot of the camera scene is taken 24 times per
second. Because of the limited speed of the human eye, these snapshots, when viewed at the
same sample rate of 24 snapshots per second, seem like continuous motion to the human eye.
Time based data logging works the same way. A snapshot of the engine state is recorded at fixed
time intervals.
RPM based logging is mainly used in conjunction with chassis- or engine-dynamometers. Their
purpose is to measure power and torque curves of an engine in relation to RPM. Typical RPM
interval is every 50 RPM. Although this serves its purpose, time-dependent dynamic effects can’t
be analyzed with this logging method.
A time based recording can be converted into an RPM based recording (LogWorks has that
capability), but an RPM based recording can’t be converted back into a time based recording.
2.1.1 Definitions
Channel
A channel is the data from a single sensor, like AFR or RPM.
Sample
A snapshot of the engine state is called a sample. A sample can contain the data of many
channels, but they are all measured ideally at the same time.
Sample Rate
The sample rate is the number of samples (snapshots) of engine data taken per second.
Channel Rate
The channel rate is the number of total channel measurements taken per second. It is the number
of sensors measured for each sample multiplied by the sample rate.
2.1.2 Logging rate
The data logging rate or speed (samples per second) is dependent on what data is to be logged.
When logging engine data, 99% of the data changes no faster than about 5 times per second
(one state to another and back).