2.1 PRODUCT SELECTION GUIDE
Datasheet information
How to interpret datasheet parameters / Which specification is crucial for a certain application?
List of all specifications with their definition and how important they are in context with the specific application.
A
Acceleration sensitivity bar/g
Inertial forces due to vibration or
shock can cause an apparent change
of the output signal. This parameter
has to be as small as possible.
The acceleration sensitivity of
water-cooled pressure sensors is
additionally influenced by the mass
of the cooling water in the pressure
sensor and tubes. It is usually
significantly higher than in uncooled
pressure sensors. For pressure measurements
at positions with high acceleration
load, such as close to the
intake or exhaust valves but also in
racing engines at high speed, pressure
sensors with low acceleration
sensitivity should be used. The sensor
is rated on its axial acceleration
sensitivity. The sensor itself could
also be effected in case of high
radial acceleration load. In this case
a sensor with dedicated construction
like GR15D should be used. Figure 1
shows an example of the influence of
acceleration on the pressure signal.
The high frequency oscillations
superimposed on the pressure signal
are caused in this specific measurement
arrangement by the impact of
the intake and exhaust valves on the
valve seat which are transmitted by
structure-borne noise.
B
Burn off resistance
The burn off resistance of a sparkplug
is limiting the electric current
between the electrodes during the
flashover. This value has no influence
on the measurement performance of
the pressure sensor.
Burst pressure bar
The burst pressure characterizes the
maximum pressure before a sensor
gets destroyed. The operating
pressure always has to be smaller to
guarantee safe operation.
C
Cable connection
The cable connection specifies the
type and size of the electric connection
of sensor and piezoelectric cable.
Most of the piezoelectric pressure
sensors are equipped with either a
M3 x 0.35 or a M4 x 0.35 connector.
Older sensor types like, e.g. some
water cooled quartz piezoelectric
sensors, use so called microdot
10-32 UNF connectors. Line and low
pressure sensors have a Bürklin - 7
pin plug. Monitoring sensors require
either an M4 x 0.35 or an M12-8 pin
connector. Our newest sensor, the
GH01D, is equipped with a M2 × 0.25
connector.
AVL does not recommend the use
of cables of other suppliers. Due to
small incompatibilities the ceramic
insulator inside the sensor gets
permanently damaged and proper
signal transmission can not be
guaranteed.
Capacitance F
In principle, the capacitance is the
ability of a device to hold electrical
charge between electrodes.
Old amplifier technologies require
this value for accurate measurements.
In state of the art indicating
measurement systems this value has
no practical relevance anymore and
therefore no influence on the signal
quality.
Cooling rate l/h
Quartz sensors require active water
cooling. The cooling rate is a constant
flow rate of the water through
the sensor at a certain pressure. This
rate has influence on the thermal
sensitivity change. That explains
also the reason why the value for the
thermal sensitivity change of sensors
with quartz material is stated in %/°C
and not in %.
Cyclic temperature drift bar
Due to the fact that the membrane
of the sensor is periodically heated
by the combustion in the cylinder the
local temperature at the membrane
Figure 1
20