Prelim Exam
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Started: Sep 19 at 9:01am
Quiz Instructions
Question 1
80 pts
1. Briefly define and explain all the static characteristics of measuring
2. How is the accuracy of an instrument usually defined? What is the difference between accuracy and precision?
3. State briefly how the dynamic characteristics of an instrument affect its usage .
4. A tungsten resistance thermometer with a range of –270 to +1100°C has a quoted inaccuracy of ±1.5% of full-scale reading. What is the likely
measurement error when it is reading a temperature of 950°C?
5. A batch of steel rods is manufactured to a nominal length of 5 meters with a quoted tolerance of ±2%. What is the longest and shortest length of rod
to be expected in the batch?
6. What is the measurement range for a micrometer designed to measure diameters between 5.0 and 7.5 cm?
7. A tungsten/5% rhenium–tungsten/26% rhenium thermocouple has an output e.m.f. as shown in the following table when its hot (measuring) junction
is at the temperatures shown. Determine the sensitivity of measurement for the thermocouple in mV/°C.
mV
4.37
8.74
13.11
17.48
°C
250
500
750
1000
8. Define sensitivity drift and zero drift. What factors can cause sensitivity drift and zero drift in instrument characteristics?
(a) An instrument is calibrated in an environment at a temperature of 20°C and the following output readings y are obtained for various input values x:
y
13.1
26.2
39.3
52.4
65.5
78.6
x
5
10
15
20
25
30
Determine the measurement sensitivity, expressed as the ratio y/x.
(b) When the instrument is subsequently used in an environment at a temperature of 50°C, the input/output characteristic changes to the following:
y
14.7
29.4
44.1
58.8
73.5
88.2
x
5
10
15
20
25
30
Determine the new measurement sensitivity. Hence determine the sensitivity drift due to the change in ambient temperature of 30°C.
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