Sample Problem Set 1
Weigh Scales Project
Keywords - Strain Gauge,
Strain, Wheatstone Bridge, Static Characteristics (Sensitivity, Offset, Range,
Max Non Linearity)
1. Explain the principle of operation of the electrical strain gauge
2. Explain what is meant by the following terms
Strain
Gauge factor
3. In the context of weight measurement using strain gauges in a Wheatstone bridge, explain the difference in arranging one, two or four gauges in the bridge.
4. A load cell using strain gauges in a Wheatstone bridge arrangement was tested in the laboratory and the following set of results were obtained.
|
Mass (g) |
Output (mV) |
|
0 |
2.7 |
|
50 |
2.8 |
|
100 |
3 |
|
150 |
3.4 |
|
200 |
3.9 |
|
250 |
4.4 |
|
300 |
4.9 |
|
350 |
5.2 |
Plot these results and determine the following
Sensitivity
Offset
Max non linearity
5. (i) Determine the output from the Wheatstone bridge below if the gauge factor is 2.1, unstrained resistance is 120Ω, and the strain is 1000 microstrain:
Where R1, R2 and R3 = 120 Ω and bridge supply voltage is 10 V. R4 is the strain gauge
(ii) What is the purpose in making R2 a variable resistor?