LabVIEW Assignment: Simulated Devices and Thermistor Sensors

Creating and Using Simulated Daq Devices

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.

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.

Instructions to Students:

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.

This assignment is marked according to the relevant grid included with this assignment brief.

3. 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.

. 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.

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.

A strain gage mounted on a cantilever beam is used to measure its deflection. The strain gage is mounted on a Wheatstone bridge, and the bridge’s output voltage is measured using a Daq device. Assume that the strain gage used has a resistance value of 120 ? and a gage factor of 2. If the excitation voltage of the Wheatstone bridge is 10V:

1. Draw a schematic representation of the circuit. What should be the resistances’ values for the remaining three arms of the Wheatstone bridge?

2. What should you consider adding to your circuit before connecting it to a Daq device? Explain why?

3. Design and implement a VI to acquire the output voltage using a simulated Daq device.

4. Explain which simulated Device you chose and why?