DA6503.005
14 December 2016
APPLICATION INFORMATION
Temperature Measurement Configuration
In the temperature measurement configuration the piezoresistive sensor RS is connected into a Wheatstone
resistor bridge configuration together with four internal resistors R1, R2, R3 and R4. See figure 7.
VDD
RS
R3
R4
R1
R2
NI
PI
VIN
GND
Figure 7. Temperature Measurement Configuration
In the temperature measurement configuration the A/D converter input signal has the following characteristics.
1
1
VIN
T
VDD
Equation 5.
R
RS
R4
1 TCS
T TREF
T TREF
R3
R4
1
1
1
R2
1 TCR
VDD = supply voltage
RS = sensor bridge resistance []
R1, 2, 3, 4 = internal resistors []
TCS = sensor resistance temperature coefficient [ppm/C]
TCR = internal resistor temperature coefficient [ppm/C]
TREF = reference temperature for resistor values [C]
T = actual temperature to be measured [C]
From equation 5 we get that the temperature signal has a rising temperature dependency vs. temperature when
the sensor resistance has a positive temperature coefficient TCS>0. With negative sensor resistance
temperature coefficient TCS<0 the signal has a falling temperature dependency vs. temperature. See the signal
illustration in figure 8.
Figure 8. Temperature signal dependency of sensor resistance temperature coefficient
26 (34)
MAS [ MICRO ANALOG SYSTEMS ]
