Siemens VDO modulcockpit II Product Manual page 93

Technical Product Manual
VDO modulcockpit II
5. Testing Instructions
5.7 Electronic Tachometer
With Operating Hours Counter
Test method description:
Test of operating hours counter
Connect the instrument per test circuit diagram II with the test cable with 10-pole connector housing and the
measuring cable.
After connection of the operating voltage the display shows the operating hours. The operating hours are coun-
ted and displayed if, in addition, an engine speed signal is connected.
The comma flashes once per second at engine speeds above 400 rpm.
The time unit count cannot be erased.
Test of pointer position: test of the zero point
Connect the instrument per test circuit diagram I with the test cable with 10-pole connector housing.
Check the pointer position after connection of the operating power. The deviation shall not exceed
± 1 degree of angle.
Test of pointer position: test of full scale deflection
Connect the instrument per test circuit diagram II with the test cable with 10-pole connector housing and the
measuring cable.
Connect a square wave signal with a frequency calculated with the follwing formula to pin 4 of the connector.
The amplitude can have any value between 1 and 10 V.
Formula for number of pulses per revolution:
Formula for the frequency:
Example:
Tachometer with scale-end at 3000 rpm, 4 cylinders 4-cycle engine, 1 ignition coil
TU00-0740-0000002
pulses 2 x number of cylinders
( )
=
revolution cycles x number of ignition coils
pulses
( )
revolution x scale-end speed
f =
max
60
pulses 2 x 4
=
4 x 1
revolution
2 x 3000
f
=
max
60
0904
333-251-980-. . .
[Hz]
= 2
= 100 Hz
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