In the tank measurement example, which voltage represents 8 feet of water?

• A. 4 V
• B. 1 V
• C. 5 V
• D. 3 V

Answer: (A)

Voltage from a tank level sensor is proportional to the water height. If the sensor is calibrated so 0 feet equals 0 volts and the full height (10 feet) equals 5 volts, then the output scales linearly with height. Eight feet is 80% of the full scale, so the voltage is 0.8 × 5 V = 4 V. Thus 4 volts represents 8 feet. For reference, 1 V would map to about 2 feet, 3 V to about 6 feet, and 5 V would indicate the tank is at full height (10 feet).