TD80™ Level Gauging and Overfill Prevention System Product Manual
Rev. 2, August 4, 2015/ TD80 Programming Page 127
6 TD80 Programming
6.1 TD80 Transmitter and Probe Description
The TD80 transmits a continuous stream of radio frequency pulses into the probe. These
pulses travel along the probe and part of the pulse energy is reflected back to the
transmitter when encountering the surface of the liquid in a tank. Time delay between the
transmit pulse and reflected pulse is used to calculate the distance from the tank top
mounted transmitter to the liquid level.
The TD80 contains a table describing the tank depth and volumetric characteristics. This
table is programmed before installation and operation on the tank. Liquid level is
calculated from the table using maximum depth of the tank and distance from the top to
the liquid surface. The TD80 “sees” the depth of air space in the tank and calculates the
loaded volume. This table is known as a Depth Chart.
Physical limitations of Guide Wave Radar creates a dead band at the bottom of the probe
where the transmitted pulse interferes with the reflected echo. This region of dead band
is considered to be the bottom 5.5” of the tank. Any liquid level measured at 5.5” or less
is indicated by the Finch as “2 LO”, meaning “too low”. An upper dead band exists at 7.5”
from the top on the dual rod and 2.5” on the coaxial probe. Level measurements within
the dead bands are inaccurate and unreliable.
Calculated volume is transmitted to a Finch display by SV Bus while a linearly scaled
level is sent by the optional 4-20mA interface. The Finch is able to display up to 4
numeric digits, including a decimal point. This numeric display correctly indicates volume
of loaded product in the tank. The 4-20mA output is scaled linearly for a volume of 0% at
an output of 4mA and 100% volume at 20mA.
6.2 Programming the TD80
The TD80 must be programmed before use.
Programming may be done at the factory when purchased, by the customer prior to
installation or after installation on the vehicle when necessary. If the TD80 is not
programmed to the specific parameters of the tank it is measuring; it will not provide
useable and accurate readings.
The TD80 transmitter is most conveniently programmed on a workbench close to a
computer, AC power and a setup to test the transmitter for correct operation.
The TD80 can also be programmed in place on the vehicle. Battery power from the truck
or the AC power adapter supplied with the programming adapter may be used. The AC
adapter easily powers the TD80 transmitter and Finch display.
Programming through the Finch 5332E (green terminal board) requires vehicle battery
power to be disconnected at the display terminal board when using the AC adapter.
Vehicle power and accessories are disconnected by removing the wired plugs from the
terminal board mounted sockets. The Finch 5332E/PS (red terminal board) has a
dedicated programming connector that isolates AC adapter power from the rest of the
vehicle and accessories such as horns and lights.
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