Rack Monitor 8800E/8801E
Document: Operation Manual
Date: 16-Jun-2011
Version: A.6
Page 15 of 35 H71343
Sensors Types.
Two-Wire Thermistor Sensors. (NTC)
Two-Wire sensors.
Five-Wire sensors.
Sensors and Grounding.
Before continuing describing the functionality of the rack monitor a short explanation of the sensors and ground
verification.
As mentioned above there are three industrial standard sensor principals.
There are two industrial standards for the Two-Wire sensors.
A Thermistor sensor with a negative temperature coefficient (NTC) and a Two-Wire optic or compatible sensor. The
Thermistor sensor is basically a heating element in combination with a temperature sensor.
The Thermistor sensors are heated up to approximately 75°C (167°F) (Depending type).
Time to heat the sensor depends on ambient temperature and used Thermistor type.
( how the 8800E will handle the Thermistor is explained later in this document).
The sensing circuit of a 2 (and 5) wire sensor are not necessarily done with a optic detection circuit. To avoid
misunderstanding this manual will refer to Two-Wire sensors and Five-Wire Sensors. Two-Wire sensors can be
used on vehicles with no more then eight compartments. Standard Rack monitors are monitoring all 8 channels
(see Dipswitch setting for 6 channels US version). This means remaining channel(s) on vehicles equipped with
Two-Wire sensors with less then 8 compartments must be connected to a electronic Dummy (e.g. part number
1920). All sensors are individual Wired / connected to the Rack monitor and more than one wet compartment can
be detected at the same time.
The Five-Wire sensors are connected in series and therefore capable of handling more then 8 compartments.
Because of this, only one wet compartment can be detected at the same time. A special diagnostic wire is used to
determine the wet compartment. The 8800E can handle more then 12 compartments but only 12 will can be
indicated on the LED display.
(Maximum 12 compartments according EN13922)
The 8800E will try to determine which compartment is wet if more than 12 compartments are used and if a good
connection is made between plug and socket and wiring are done carefully, the 8800E shall indicate the correct
compartment on the Liquid Crystal Display.
Note: Displaying the correct wet compartment is only possible if there are no bad connections.
Ground verification is done via pin 9 on the terminal and plug-socket connection.
For NEN-EN13922 application pin 9 is also used for detecting if a Vapour recovery hose is properly connected to
the Tank-Truck when five-Wire sensors are used.
Note: The Vapour recovery hose is checked via pin 8 on a Tank-Truck equipped with Two-Wire sensors.
Note: Consult socket drawings for detailed information.
The 8800E Rack Monitor is capable of (auto-)detecting a resistive Ground connection as well as a Ground-Bolt
(EL00001-E) connection on a Tank-Truck. Make sure connection between pin 9 and pin 10 via the Tank-Truck
chassis is less then 1k
Ω
.
The two wire Thermistor sensors are simple component sensors with no active elements. This means the Rack
monitor has to control the Thermistor sensor where a two-wire optic or compatible sensor has active elements and
is self oscillating when dry.
As soon as the 8800E rack monitor has detected the Thermistor sensor it will supply power to heat the Thermistor
bead from ambient temperature to a predefined high temperature this will be indicated on the LC-Display with a “H”
and also the green indicators will flash from low intensity to high intensity. As soon as the thermistor bead reach the
predefined high temperature the 8800E will switch off the power. The Thermistor will cool down until the predefined
low temperature is reached. When a the Thermistor bead becomes wet the 8800E is not able to heat the Thermistor
bead within the specified time and switch to NON-permissive.
