Instrumentation Measurement & Lab

Temperature Alarm Project

Part 1

1. A temperature sensor is exposed to a sudden change of 20^oC to 80^oC. The sensor outputs 0.02 volts for every ^oC of temperature and has a 2.3 second time constant.

a. What is the sensor output voltage at 1.5 seconds?

b. At what time, t, does the sensor output become 1.0 volt?

2. A sensor, R, that changes resistance is used in a bridge circuit as shown below.

a. What sensor resistance, R, will null the bridge?

b. What is the off-null voltage if R changes by 0.5 Ω?

3. A measurement system has noise above 20 kHz and the data signal frequency is between 100 and 500 Hz. Design an RC filter that reduces the noise by 95%, i.e., only 5% is left. Show the schematic and the component values.

4. Given a Type J TC with a 25^oC reference.

a. What is the temperature if the TC voltage is 22.87 mV?

b. What voltage would result from a temperature of 225^oC?

5. A 10-bit ADC has a 5.00-volt reference.

a. What binary output is produced by an input of 3.04 volts?

b. Suppose the output is found to be 1F4h. What is the possible input voltage?

6. A 12 bit bipolar DAC has a 10-volt reference.

a. If the hex input is 5D7h what is the DAC output voltage?

b. What input is required to get a zero volt output?

Part 2

1. A golfer estimates that his golfball is  250 yards to the hole.  At the hole, another golfer has dropped a water bottle that is reflecting light back to the golfer and his ball.  What is the approximate time difference based on golfers distance to the hole/water bottle?

2. A CdS photocell has a resistance versus light intensity as shown in the following graph.  The cell has a time constant of 25 ms.  At t=0, the cell is exposed to a sudden change of light intensity 20 W/m² to 80 W/m².  What is the sensor resistance after 20 ms?

Figure 1: CdS Resistance Versus Light Intensity

3. A force of 120 pounds-force is used to open a valve. What is the area of the diaphragm if the pressure difference is 90 kPa (~ 13 psi) that must provide this force?

4. A processing plant is being proposed and will need to use of the city's water system to be sucessful.  The plant will need a minimum of 2500 gallons of water per minute (gpm) for its operation.  The city's current water supply pipe to the proposed plant is 12 inches in diameter with a water velocity of 1.5 m/s.  Will the city's current water supply meet the plant's needs or will it need to be upgraded?  Show calculations to verify your answer.

5. From the figure below, construct the truth table for the logic diagram. What function does this represent?