Datasheet

SBOA102A
January 2005
Sensor-Emulator-EVM
System Reference Guide
10
Figure 2.6 illustrates one method for monitoring the temperatureof a real world bridge sensor. In this type of circuit the resistance of the bridge
has a strong temperature coefficient. The bridge resistance generates a bridge current with a strong temperature coefficient, which generates a
voltage across the temperature sensing resistor (Rt). Rtis typically located remotely from the bridge and should not have a strong temperature
coefficient. Note that Rtcan be connected to the top or bottom of the bridge. This diagram illustrates the case where it is connected to the bottom
of the bridge. The sensor emulator circuit has three channels to emulate the Rttemperature signal that are selectable through a rotary switch.
An important aspect of the Rtmethod of temperature sensing is the reduction of the excitation voltage across the bridge by the series Rt
resistance. For example, if Vt= 1V and Vexc= 5V, then only 4V remains for the bridge excitation. This phenomena is modeled by the sensor
emulator and the detail of how this works are described in Figure 2.15.
(R
t-
connected to
the bottom of
the bridge)
Figure 2.6 Figure 2.7 Figure 2.8
V
T
V
exc
R
T
⋅
R
T
R
Bridge
+
Emulating a Temperature Sensor
with a Series Bridge Resistor