Practice Questions

  1. I have a non-linear device that cannot handle more than 20 mA of current passing through it. When powered, the voltage drop is 1.7 V.  It will be powered by a 9V battery.  Draw a circuit containing a current limiting resistance, and calculate the minimum resistance required to avoid damaging the device.


  1. Develop a truth table for the expression: X = AB’ + C’. Draw the relevant logic circuit.


  1. Explain Nyquist Theorem, what it means to instrumentation, and what happens if you ignore it when sampling data.


  1. Explain how linear regression might be used to verify the calibration of a sensor.


  1. A certain pressure sensor sends a 4-20mA signal to represent steam pressure of 200 psi-1000 psi. Generate a linear equation that calculates pressure for any given current.


  1. Explain how a pressure sensor can be used to measure flow rate. Also explain how it might be used to measure fluid level in a tank.


  1. Compare and contrast thermocouples and RTDs


  1. Explain the difference between analog and digital signals.


  1. You have a sensor that generates an ADC signal of 856. This system spans from 0 to 5 Volts, and has 10 bits to store data.  What is the actual voltage out?


  1. Explain why you should measure voltage in parallel and current in series. (Hint:  a voltmeter tries to have infinite resistance and an ammeter tries to have no resistance.  If you are struggling, draw a circuit with each of these in place and then put them in the wrong places and see what happens.)