Simulated Daq Devices and Temperature Measurement - LabVIEW Technical Report

Instructions to Students

1. To create and use simulated Daq devices.

2. To acquire data from a Thermistor sensor and display the measured temperature.

3. To design and build a LabVIEW interface to the thermistor sensor circuit on Figure 1.

4. To acquire the output voltage of a Wheatstone bridge using a simulated Daq device.

5. To design and implement a LabVIEW interface to measure the change in resistance of a strain gage mounted on a Wheatstone bridge.

The assignment should be written in the form of a technical report. Write up the assignment as a technical report making sure all figures are numbered and labelled and the report is written in the third person.

Your report and LabVIEW source code are to be uploaded as separate files on Turnitin.

When submitting, please enter your student ID number in the “submission title” box.

The document itself should contain your student ID number in a header or footer; your name should not be visible on the work.

Part 1: Temperature measurement using a simulated Daq device

Procedure 1: Create a simulated data acquisition device

LabVIEW provide simulated acquisition devices that are a replica of real acquisition devices and enable you to work on simulated signals and data. For the purpose of this assessment, create one simulated devices for the acquisition of the output voltage of a Thermistor circuit.

4. Create a new VI in LabVIEW:

a. Open LabVIEW and select File >> New VI.

5. Create a simulated Daq device

a. Click on Tools >> Measurement and Automation explorer.

b. On the left under MySystem, right click on Devices and Interfaces then Create New.

c. On the popup window select Simulated NI-DAQmx Device or Modular Instrument >> Finish.

d. Scroll down to Educational Hardware and select NI MyDaq >>OK.

e. Your device should appear under the Devices and Interfaces with a yellow icon.

6. Create an NI-DAQmx task in the DAQ Assistant.

a. Right-click My System>>Data Neighborhood>>NI-DAQmx Tasks and select Create New NI-DAQmx Task. A window prompts you to select the measurement type.

7. Select Acquire signals >> Analog Input >> Voltage >> MyDaq >> ai0.

8. Detailed explanation can be found  2: Acquire data from a thermistor circuit and display the temperature on a graph

The thermistor is a resistor that changes value according to the temperature.

The relationship between the resistance of the thermistor and the temperature, T, can be described using the B-parameter equation:

The resistance is R0 when the temperature is at T0. For the thermistor on the mechatronic sensors trainer, the sensor resistance is R0 = 47000 ? when the temperature is at 25 degrees Celsius, or T0 = 298.15 K. Assume that the Bparameter B= 1200. Voff is the voltage adjusted using the Offset potentiometer and Av is the amplifier gain that can be changed externally using the Gain potentiometer.

1. Using the voltage divider rule, derive the offset voltage to null the output voltage for a gain off 1.

2. Derive the formula that can be used to find the thermistor’s resistance R from the output voltage of the circuit.

3. Derive the formula that can be used to find the Temperature T of the Thermistor.

4. Create a VI to read and display the output voltage of the circuit. Calculate and display the Temperature and the Thermistor’s resistance for 20 iterations.

a. Open LabVIEW and create a Blank VI. Switch to the block diagram (Ctrl+E).

b. The DAQ Assistant Express VI can be found on the Functions palette by going to Express » Input. Place the DAQ Assistant on the block diagram by dragging and dropping it from the Functions palette. The Assistant should automatically launch when you drop the VI on the diagram.

c. On the first screen, select Acquire Signals and then Analog Input for your Measurement Type.

d. Next, select Voltage.

e. Change the voltage range » -10 to 5 V

f. Select Iex Source to External.

g. Acquisition mode to on continuous » OK.

h. When asked to create the Loop » Yes.

i. Replace the Loop While with a For loop.

j. Add a waiting time of 500 ms

5. How does the output voltage change comparing to the change in Temperature?

6. What happens when you change the B parameter?

7. Change the For Loop to a While Loop again.

8. Give some examples of the output voltage when the Thermistor’s temperature is between 23 0C and 25 0C.