Question 4.67: High Bias Design Problem A particular pressure sensor is des......
High Bias Design Problem
A particular pressure sensor is designed to operate under constant pressure. The task is to detect a pressure increase and sound an alarm. The sensor produces 1 mV at 100 psi, its usual operating pressure, and increases by 1 μV per psi. The design must sound an alarm if the pressure reaches 150 psi. The transducer is modeled as a voltage source with a series resistor that varies with pressure from 50 Ω at 100 psi to 150 Ω at 150 psi. Two types of OP AMPs are available. Type #1 are single-sided, meaning they have a +V_{CC} of 5 V and a –V_{CC} of 0 V. Type #2 OP AMPs are double-sided with a V_{CC} of ±15 V and have a maximum closed-loop gain of 5000. The alarm can be driven with the + 5 V available from a saturated type #1 OP AMP. Only ± 15-V and + 5- V sources are available. Design the alarm circuit.
Connect the transducer model in series with a 5-V source and a 150-Ω resistor to create a voltage divider with the output across the 150-Ω resistor. As the pressure increases, the transducer resistor increases in value and the output voltage decreases. When the output voltage reaches 2.5 V or lower, we want the alarm to sound. Connect the output of the voltage divider to the negative input of a comparator circuit and connect a 2.5-V reference signal to the positive input.
Use a Type #1 OP AMP so that it produces the correct signal for the alarm. The following circuit will meet the specifications.
Answer:
Presented above.
