Here are the answers to your questions:
1. (i) True Sensors receive the variable being measured as input. (ii) True Sensors produce
an output signal suitable for processing.
2. (i) True A higher meter resistance means a larger change to the circuit. (ii) False The
lower the circuit resistance compared to the meter resistance, the bigger the impact the
meter has on the circuit.
3. (i) False Reliable systems require less frequent calibration. (ii) True Reliability means the
system performs as expected.
4. Functional elements of a measurement system:
○ Sensor/Transducer: Detects the measurand (the quantity being measured) and
converts it into a signal (often electrical).
○ Signal Conditioning: Modifies the sensor's output to make it suitable for further
processing. This might involve amplification, filtering, or conversion.
○ Signal Processing: Transforms the conditioned signal into a form that can be
easily interpreted or displayed. This could include linearization, analog-to-digital
conversion, or calculations.
○ Data Presentation: Displays or records the measured value in a way that is
understandable to the user (e.g., a digital display, a meter, a chart).
5.
○ (a) Reliability: The probability that a measurement system will perform its intended
function for a specified period under stated conditions. It's about consistent
performance over time.
○ (b) Repeatability: The ability of a measurement system to produce the same
reading for the same input value when the measurement is repeated multiple times
under the same conditions (same operator, same instrument, same location, short
time interval). It's about consistency in repeated measurements.
6. Traceability to national standards means that the calibration of a measurement instrument
can be linked through an unbroken chain of calibrations to a national measurement
standard. This ensures the accuracy and consistency of measurements across different
locations and organizations. Each step in the chain has a stated uncertainty, and the
overall uncertainty of the instrument's calibration can be determined.
7. 'Fitness for purpose' means that a measurement system is suitable for its intended
application. It considers factors like accuracy, precision, range, resolution, reliability, cost,
and ease of use. A system that is very accurate but too expensive or complex might not
be fit for purpose for a simple application.
8. A reliability of 0.6 means there is a 60% probability that the measurement system will
operate as specified for a given period of time under defined conditions. Conversely,
there's a 40% chance it might fail or perform outside specifications.
9. A failure rate of 0.01 per year means that, on average, there is a 1% chance that any
single instrument will fail within a year. This can also be interpreted as meaning that, on
average, one out of every 100 instruments is expected to fail per year.
