Case Study

HVAC Systems

Application: Level Sensing Analogue Output
Equipment: Specialist Vehicle

Challenge

To have an output proportional to the volume of liquid in the chamber, previously the customer evaluated a range of fuel senders to monitoring both diesel fuel and water levels. Due to a number of problems the customer requested Gentech to find a solution. Two types of medium were used in the application and identified as: Diesel fuel and Water. The contents indication in the cab required several cardinal points showing the contents of the tank; “Full - ¾ - ½ - ¼ - Empty”, providing this essential information to the driver, plus having preset alarm functions into the control unit.

Key Factors

Constrained by access to the tank (top only)
Tank depth
Mounted internally
Multiple Point Indication
Sensor to be compatible for Fuel and Water – completely resistant to the different fluids
The sensor should not need to be calibrated for the different mediums

Solution

There were two main considerations required during development of this product.

To ensure repeatability of the output resistance, relative to the float and liquid level
To ensure the sensor was robust and avoid damage when in operation

The product was developed using 10mm diameter brass tubing up to 500mm in length, with
single 40mm diameter Buna “N” foamed float.

Result

Product Selected: ESS Series a 500mm brass stem with analogue output

Multi switch position with single output: this was achieved by mounting a reed switch plus
resistor ladder network on a PCB fitted within the brass stem.
A resistance change progression was achieved in 10 steps to give a variable resistance
output from 10 to 180 Ohms
A single VDO instrument with LCD display was used in the vehicle calibrated to give
sequential readings of fuel and water levels, road and engine speeds.
Cable specified was 22 AWG 200mm long & terminated with a Deutsch connector.

Potential Markets

Agricultural
Commercial & Off Highway Vehicles
Electricity Generating Equipment