In this lab you will filter the signal from a pressure sensor that is used to monitor the height of liquid in a tube while the tube has an inflow and outflow.  The inflow from a pump generates turbulence that causes the output from the pressure sensor to be noisy.

        There are five experimental setups, and each setup is different.  Keep track of which unit you work with.  Here's what you need to do once you have chosen a unit.

• Apply 12v to the sensors which need a power supply.  Apply the voltage at the terminals on the circuit board as indicated.  There are two sensors - a pressure sensor and a flow sensor.  If you don't apply a voltage you will not get an output from the sensor.
• Apply a voltage to the pump to get the liquid flowing.  Aim to get the liquid at a steady state somewhere near the point where the tube is half full.
• Measure the output from the pressure sensor on an oscilloscope.
• The oscilloscope will permit you to see a time history of the pressure sensor voltage output that includes the signal and noise.  (That's somewhat like the situation in the Filter Simulator you may have used in class.)
• Estimate the magnitude of the noise by estimating the high point and low point of the noise from a complete oscilloscope trace.  (Hit the Stop button on the scope at the end of a trace.)
• Add a resistor-capacitor (RC) filter at the sensor output.  Begin by using a 0.1sec time constant.  (R = 100KW, C = 1mf)
• Observe the filter output on the oscilloscope.
• Change the time constant by varying the resistor - making it smaller.  Observe the results and draw any appropriate conclusions about what the time constant should be.