2.3. Calculate the value of the weight W of the block.

A rigid block has a weight W and is supported by two steel posts (A and B in Figure 1) and a brass post (C in Figure 1), as shown. The posts all have the same original length 2 m and cross-sectional area A = 4000 mm². 

Two strain gauges are bonded to the outer surface of each steel post and coupled in half-bridge configuration into arm 2 and arm 4 of a Wheatstone bridge.

The strain gauge factor for the strain gauge on post A is 1.9, while that on post B is 2.0.

When the temperature of the brass post C is raised by 10 °C, the Wheatstone bridge output (Vo/Vi) is 146 x10^-6 V/V.

1.1 Calculate the stress in the steel posts at this point.

1.3. Calculate the stress in the tube when the bridge output voltage is 5 mV.

1.2 Determine the elongation of the tubing when the bridge output voltage is 5 mV.

A 350 Ω strain gauge (K = 1.8) is bonded to the outside surface of a 0.8 m length of steel square tubing (outer dimensions 19 x 19 mm, wall thickness 1.6 mm). The strain gauge is coupled in quarter-bridge configuration into a Wheatstone bridge amplifier. A 10 kΩ shunt resistor is coupled in parallel over the strain gauge in order to calibrate the set up. The input voltage to the bridge is 6 V. 

1.1 Calculate the calibration output voltage.

What colour wire is connected to the P+ terminal of the instrument used to observe the strains?

What lab instrument is used to observe the strains measured by the strain gauge?

What approximate reading should you observe while checking if the strain gauge works?

Which of the following apparatus is used to check whether the strain gauge is correctly set up?

What would cause a short circuit?