instructions: COVENTRY UNIVERSITYFaculty of Engineering, Environment and Computing
Instrumentation and Control (210MAE)
Hand in date 21-04-2016
Question 1
A mass measurement system was calibrated at two temperatures, 20C and 80C using
kilogram masses. The third stage device instrument was set to 20 mV range, and the
following readings were taken:
Input mass
(kg)
Output at 20°C
(mV)
Output at 80°C
(mV)
Mass
increasing
Mass
decreasing
Mass
increasing
Mass
decreasing
0.00 0.00 0.12 2.25 2.35
0.50 3.36 3.48 5.61 5.71
1.00 6.36 6.48 8.61 8.71
1.50 9.22 9.34 11.47 11.57
2.00 13.00 13.12 15.25 15.35
2.50 15.98 18.23
a) By plotting the appropriate results on a graph, determine the static sensitivity of the
measurement system at 20C with mass increasing, over the range 0 to 2.50 kg. Give
your answer in mV/kg. (15 marks)
b) For the range 0 to 2.50 kg, estimate the non-linearity at 20C with mass increasing, as
an appropriate percentage. (7 marks)
c) Calculate the zero drift as an appropriate percentage. (9 marks)
d) Calculate the hysteresis at 20C as an appropriate percentage. (7 marks)
e) Calculate the resolution of the measurement system. Give your answer to the nearest
gram. (12 marks)

Question 2
Figure Q2 shows a strain gauge bonded to a piece of aluminium sheet under a tensile force.
The gauge has been selected to be self-compensating for temperature but the leads to and
from the gauge are subject to temperature variations of 30C.
The strain gauge and the metal have the following properties:
Gauge specification Aluminium specification
– Gauge factor =2.2
– Resistance =120  0.5 
– Maximum current = 30 mA
– Young’s modulus =69 GN/m2
– Poisson’s ratio = 0.32
a) Draw a circuit diagram showing how the strain gauge can be connected into a bridge
to measure the strain in the aluminium. Your circuit should show the gauge, the leads
to and from the bridge, the bridge power supply, and a means of balancing the bridge.
Adequate annotations and labelling of the circuit is expected. (10 marks)
b) Calculate the permissible maximum bridge output voltage V2 for the bridge when the
force F is 1.5 kN. (10 marks)
c) Show on a diagram how by adding additional gauges to the piece of metal and by
suitable arrangement in a bridge the force F can be measured with the maximum
sensitivity. (You need only draw the gauge positions on the metal and in the bridge;
leads need not be shown.) (5 marks)
d) Calculate the maximum permissible bridge output voltage V2 for the bridge in part (c)
when the force F is 1.5 kN. (10 marks)
e) Calculate the maximum permissible bridge output voltage V2 for the bridge if gauge
specification change to; resistance 350 ±0.5 Ω, maximum current 40 mA and, force F
2.0 kN.
(15 marks)

F F
4 mm
25 mm
80 mm
Figure Q2