Strain Gage Lab

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Strain Gage Mounting and Utilization September 9th, 2008 Introduction: The experiment was aimed at teaching the students the about mounting and testing strain gages in a real application. The gages were used to mount onto a beam. The resistance changed as the beam was subjected to a bending moment, stretching the beam face and gage. A digital readout of the gage was displayed and aloud students to measure the strain in the beam. After the gage was securely adhered to the beam, a 2000 micro strain moment was applied. The read-out showed the strain to be 1966 micro strain. Instrumentation: 1. Strain Indicator – Precision Measurments Co. 2. M-Bond 200 3. 1”x1/4”x13” aluminum bar 4. Strain gage CEA-13-240UZ-120 (factor 2.1) 5. Loading device MFG Magnaflux Corp. (Stresscoat 24870) 6. Fluke Multimeter 7311 Procedure: The 2000 micro strain exists right at the fulcrum point and fades off towards the end of the bar. The gage was mounted over the fulcrum of the testing rig with about 40% towards the short side, and 60% towards the long side of the beam. The solder and wires were left facing the operator at the long end of the beam. Mounting of the gage follow a procedure given by Vishay Measurements Group in 309E “Student Manual for Strain Gage Technology” These are the exceptions to the directions: No solvent was used for pre-abrasion, or catalyst for the adhesive. To check the circuit, a ohm meter was hooked up across the two leads to check for 120 ohms and each lead to ground was checked for infinite resistance. The manual also outlined the attachment of a single gage. No M-coat A was used because long term protection was not needed. To find the shunt calibration, a data sheet was referenced in class received as a handout. For a 2.1 gage factor, a shunt of 1904 must be used. Results:

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