2.1 PRODUCT SELECTION GUIDE
The overload is the maximum value
of pressure which the sensor can
withstand for short time periods. It is
above the maximum pressure of the
At high pressures within the overload
range it cannot be guaranteed
that the sensor signal works according
to the specifications but the
sensor is not permanently damaged.
Pipe oscillations Hz
The indicating channel represents an
acoustic resonator which is excited
by changes in pressure and produces
oscillations. This effect is illustrated
in Figure 3 where the measured
pressure curves relate to indicating
channels of different lengths. Five
pressure curves from single cycle
measurements are shown for each
indicating channel length. They have
been shifted in level to provide a
Resistance of insulator (spark-plug)
This is the ohmic resistance between
the center electrode and the ceramic
body of the insulator.
Acronym for Sensor Database that
is part of the SDM Sensor Data
The SDB is a central digital repository
for the management of the
sensor specific data. This point can
be either a local- or a network database.
For each sensor all calibration
data is stored, the total number of
performed cycles is monitored and
service intervals can be scheduled
according to the testing needs.
Acronym for Sensor Data Connector
that is part of the SDM Sensor Data
The sensor is connected to a piezo-input
cable which has a special plug
with built-in electronics. The difference
to SIC is that the SDC does not store
only the serial number but also all
calibration data of the sensor. No connection
to any database or calibration
file is required. On the other hand the
data is only accessible locally and no
additional information can be stored.
Acronym for Sensor Data Management.
For an overview please refer
to page 15.
DIN1319 defines sensitivity in this
context as the ratio of generated
electrical charge per pressure unit
(bar). This value should be at least
10 pC/bar for high accurate measurement
data (e.g. heat release
The electrical charge is measured in
Coulomb (1 C = 1012 pC).
The nominal sensitivity is the measured
sensitivity at 23 °C.
It might seem to be important to
choose a sensor with very high sensitivity.
In fact sensitivities in the range
of 10 to 20 pC/bar are by far sufficient
especially with modern charge
amplifiers. Practically, choosing sensors
with very high sensitivities can
lead to unwanted signal overloads
during measurements, especially
under supercharged or knocking
Shock resistance g
The maximum acceleration a sensor
can withstand without being permanently
damaged. The higher this
value the more rigid the sensor is
against mechanical shocks.
In application fields with extremely
high engine speeds (racing) the
valve closing noise can cause significant
influence on the measurement
The shock resistance is measured in
units of the gravitational acceleration
which equals to 1 g = 9.81 m/s2 .