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8.2 TVC volume conversion device (Temperature compensation device)
8.2.1 System Description
The TVC is a conversion device for use with two meters, intended for correcting volumes of
fuel as if dispensed at 15°C. The temperature compensation function is added by connecting
the TVC unit between the pulse output of the dispenser pulser and dispenser calculator. The
TVC provides a pulse output stream corrected for temperature by monitoring the temperature
of the fluid passing through the meter. The pulse output is no longer a fixed number of pulses
per rotation of the meter output shaft, but adjusts the volume of fuel as if it is dispensed at
15°C. The TVC unit is shown in figure 56.
The conversion calculation for a certain density of fuel is determined by the selection of a
suitable density block (module) as shown in figure 58. The density block contains the
calculations as specified in the ASTM manual D1250-80, table 4. The density blocks are
identified as follows:
8.2.2 Construction
8.2.2.1 TVC unit
The TVC circuit board is housed in a secure box which prevents unauthorised access to the
calibration button and the power supply, data link, temperature sensor, density block and pulser
connections. The box has a clear lid to allow inspection of the density block.
Optionally an LCD display (figure 57) may be installed which allows access to the following
data by pressing the scroll button:
- Fixed Density
- Temperature (Actual temperature from liquid)
- Uncompensated volume 1(last delivery, 2 digits behind the comma)
- Uncompensated volume 2(last delivery, 2 digits behind the comma)
- When test button is pressed, display shows “bypass”
- Display shows “ERROR” when the TVC is defective or errors occur
8.2.2.2 Temperature sensor
A temperature sensor manufactured by E. Meurs BV and designated LM335 is connected to
the TVC unit. The temperature sensor (figure 59) is installed in the fuel delivery pipe within
one metre from the flow meter; a typical installation is shown in figure 60.
(98 pages)
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