Circuit for protecting pressure sensor against excess voltage - has bridge circuit with four resistors, located via temp.-dependent resistor between supply voltage and earth

摘要

The one diagonal of the bridge circuit is connected to the supply voltage and the other diagonal with the two inputs of an operational amplifier. The output of the operational amplifier and the output at which the measurement signal is measurable are decoupled from one another by a current level circuit. The current level circuit comprises two transistors (T1, T2), the bases of which are joined to one another and to the first transistor collector (T1). Their emitter is connected to earth via resistors (R23, R24) and the collector of the second transistor (T2) is connected to the output terminal. A temp.-dependent resistor (R14) is connected between the supply voltage terminal and the sensor (S). ADVANTAGE - Voltage spikes, reverse connection of supply voltage, or short circuit of output to supply voltage do not damage sensor.