Measuring device for a motor vehicle
The invention concerns a device ( 1 ) for measuring at least one parameter of a motor vehicle, the device ( 1 ) comprising at least one reference resistor (R 0 ) of a predetermined value and at least two measuring branches (K 1 , K 2 ), each of the two measuring branches comprising at least a first element comprising a resistor (R 0 ) or a resistive sensor (R 2 ), capable of being connected to a voltage supply (Vcc), and a second element comprising a resistor or a resistive sensor (R 1 , R 3 ) capable of being connected to earth (M), the first element and the second element being connected together at a mid-point (A, B), the mid-points (A, B) of the at least two measuring branches (K 1 , K 2 ) being connected together in pairs by a third element comprising a resistor or a resistive sensor (R 4 ).
1. A device for measuring at least one parameter of a motor vehicle, said device comprising at least one reference resistor of a predetermined value and at least two measuring branches, each of said at least two measuring branches comprising at least a first element comprising a resistor or a resistive sensor, able to be connected to a voltage supply, and a second element comprising a resistor or a resistive sensor able to be connected to a ground, the first element and the second element being connected to one another at a center tap, the center taps of the at least two measuring branches being connected to one another in pairs by a third element comprising a resistor or a resistive sensor, said device comprising a control module able to:
a) connect the center tap of the second measuring branch to the voltage supply or to ground,
b) measure the value of the voltage defined between the center tap of the first measuring branch and ground,
c) calculate the resistance value of the first resistive sensor and the resistance value of the fourth resistive sensor from:
d) a voltage value measured between the center tap of the first measuring branch and ground when the center tap of the second measuring branch is connected to the voltage supply,
e) a voltage value measured between the center tap of the first measuring branch and ground when the center tap of the second measuring branch is connected to ground,
f) a value of the supply voltage and
g) the predetermined value of the reference resistor,
h) determine the measurement of the parameter measured by the first resistive sensor and the fourth resistive sensor,
i) connect the center tap of the first measuring branch to the voltage supply or to ground,
j) measure the value of the voltage defined between the center tap of the second measuring branch and ground,
k) calculate the resistance value of the second resistive sensor and the resistance value of the third resistive sensor from:
l) a voltage value measured between the center tap of the second measuring branch and ground when the center tap of the first measuring branch is connected to the voltage supply,
m) a voltage value measured between the center tap of the second measuring branch and ground when the center tap of the first measuring branch is connected to ground,
n) a value of the supply voltage and
o) a resistance value of the fourth resistive sensor,
p) determine the measurement of the parameter measured by the second resistive sensor and the third resistive sensor.
2. The device as claimed in claim 1 , the maximum number of resistive sensors being given by the following equation:
Nb
=
(
(
n
+
1
)
×
(
n
+
2
)
2
)
-
2
where n is the number of measuring branches (K 1 , . . . Kn).
3. The device as claimed in claim 1 , said device comprising a single reference resistor.
4. The device as claimed in claim 1 , said device comprising at least two resistive sensors.
5. The device as claimed in claim 1 , wherein each measuring branch comprises at least one resistive sensor.
6. The device as claimed in claim 1 , wherein the second element of each measuring branch is a resistive sensor.
7. The device as claimed in claim 1 , wherein the first element consists of a resistor or of a resistive sensor and the second element consists of a resistor or of a resistive sensor.
8. A motor vehicle comprising a device as claimed in claim 1 .
9. A method for measuring one or more parameters of resistive sensors in a motor vehicle, said method being implemented by a device as claimed in claim 1 installed in said vehicle and said method comprising:
connecting the center tap of the second measuring branch to the voltage supply,
measuring the value of the voltage defined between the center tap of the first measuring branch and ground,
connecting the center tap of the second measuring branch to ground,
measuring the value of the voltage defined between the center tap of the first measuring branch and ground,
calculating the resistance value of the first resistive sensor and the resistance value of the fourth resistive sensor from the voltage value measured between the center tap of the first measuring branch and ground when the center tap of the second measuring branch is connected to the voltage supply, the voltage value measured between the center tap of the first measuring branch and ground when the center tap of the second measuring branch is connected to ground, the value of the supply voltage and the predetermined value of the reference resistor,
connecting the center tap of the first measuring branch to the voltage supply,
measuring the value of the voltage defined between the center tap of the second measuring branch and ground,
connecting the center tap of the first measuring branch to ground,
measuring the value of the voltage defined between the center tap of the second measuring branch and ground,
calculating the resistance value of the second resistive sensor and the resistance value of the third resistive sensor from the voltage value measured between the center tap of the second measuring branch and ground when the center tap of the first measuring branch is connected to the voltage supply, the voltage value measured between the center tap of the second measuring branch and ground when the center tap of the first measuring branch is connected to ground, the calculated resistance value of the fourth resistive sensor and the value of the supply voltage,
determining the measurement of the parameter measured by the first resistive sensor, the second resistive sensor, the third resistive sensor and the fourth resistive sensor.