ETAS
Digital Input Channels ("DI" Connection)
ES930.1
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User Guide
43
5.2.7
Calculation of the Speed
Application
In the automotive sector, the measurement of the rotational speed of wheels,
gears, fans, water pumps, and turbines is decisive, e.g. to be able to determine
the vehicle speed or the flow rate.
To determine the speed in revolutions per minute, an expanded configuration
of the number of periods per revolution is required.
Measuring Procedure
In the application software, parameters and measuring procedures can be
selected for the time measurement for every measuring channel:
• Measurement of the duration of the last period
• Measurement of the duration of the last cycle
Simplified Example
A speed sensor wheel with 60-2 teeth installed on the crankshaft furnishes a
periodically structured signal pattern via a sensor. The number of revolutions
per time unit is a measure for the speed of the wheel. This wheel with the 60-
part division generally has 58 teeth. The position of the two missing teeth
defines the reference mark for the position of the crankshaft. A revolution of the
wheel is described by a cycle consisting of 60-2=58 periods. The configuration
principle is illustrated using the following simplified example.
Fig.
5
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17
16-2 "Speed Sensor Wheel"
To be able to determine a speed from periodic signal forms using the ES930.1,
a cycle can be defined in the configuration software, e.g.:
1 revolution = 1 cycle = (16-2) periods = 14 periods
NOTE
The calculation of the speed is done application-specific in INCA or in the RP
model from the values for the active and inactive time determined by the
ES930.1.