tutorialpoint.org

# Instrumentation and Control Lab

### Ex 2: Measurement of Strain Using Strain Gage (Cont'd...)

#### 2.3 Procedure and Experimental Results:

(v) Plot the output voltage with displacement of cantilever beam. You may subtract the bias voltage from the readings if necessary. Calculate the slope in volt/mm.

(vi) Knowing the amplifier gain and the bridge supply voltage; (given that G=2.2 for the gage in use and Rst gage=120 ohm) calculate strain in each reading. Now plot strain with the output voltage values. From the graph calculate the change in output voltage to the change in strain, ie volt output per unit strain change.

(vii) Now displace the cantilever beam arbitrarily. Observe the output voltage. From the graph calculate the strain in the beam. Now calculate the theoretical value of the strain and compare the both.

(viii) Connect the circuit as shown in figure 2 using two strain gages.

(ix) Repeat the steps from (iii) to (viii). Compare the sensitivity in both the cases.

#### 2.4 Few Questions for Viva Voce:

(i) What are the different types of material used for strain gage? How the gage is fixed with the specimen under measurement?

(ii) What is semiconductor strain gage? What are the advantages and disadvantages of that?

(iii) State the advantages of using dual strain gage instead of single one? What is dummy gage?

(iv) Can the strain gage be used as an extensometer or to measure force and torque?

#### 2.5 Reference:

(i) Feedback manual, “complete transducers kit TK2942-001”.
(ii) E O Doebelin and D.N. Manik, “Measurement systems”, Tata McGraw Hill, special Indian edition, 2007.
(iii) A.D. Helfric and William D. Cooper, “Modern electronics instrumentation and measurement techniques”, PHI learning private limited, New Delhi.