1. Name the sensor, transducer, and readout stage for a regular ruler. What property of a ruler
allows the measurement of length?
Sensor – the physical ruler markings
Transducer – eyes and brain, which convert the markings into meaningful information
Readout stage – the numbers associated with the markings; these are what the transducer reads
The calibrated markings and associated values along the ruler are what allow it to measure
length.
2. You attempt to determine the validity of a bathroom scale by repeatedly placing 20 lb of
accurate weights on it. Ten readings were obtained with values of 20.2, 20.2, 20.6, 20.0,
20.4, 20.2. 20.0, 20.6, 20.0, and 20.2 lb. Estimate the systematic error and the maximum
random error of the measurements.
Weight: 20 lb
Average measurement: x= (204.4/10) =20.44 lb
Systematic error: 20.44 – 20 = 0.44 lb
Maximum random error: (|20.6 - 20.44| , |20.0 – 20.44|) >>> max is the greater of the two
differences so 0.44 lb is the max random error
3. You have two temperature gages available to you. One measuring 100-500°C and the other
with a range of 100-1000°C. Each has an uncertainty of 2% of its span (range of variation).
To measure a temperature of about 300°C, which of the two will you choose? Why?
The one measuring 100-500, because the smaller measurement range leads to a smaller absolute
uncertainty. 2% * 400 = 8, but 2% * 900 = 18. Plus/minus 8 is a much better uncertainty.