Measurement Instrument Characteristics Explained

Understanding how measurement instruments work involves knowing their key characteristics. The question asks for a specific characteristic related to how an instrument's reading changes when the quantity it's measuring changes. Let's break down the options:

Key Measurement Terms

• Sensitivity: This term refers to how responsive an instrument is to changes in the measured quantity. Specifically, it's the ratio of the change in the instrument's output reading to the change in the input quantity that caused it. Mathematically, sensitivity ($S$) can be represented as: $$S = \frac{\Delta \text{Output}}{\Delta \text{Measured Quantity}}$$ A higher sensitivity means a larger change in output for a small change in input.
• Linearity: This describes how closely the actual output of an instrument follows a straight line when plotted against the input quantity over its operating range. Perfect linearity means the output changes proportionally to the input.
• Hysteresis: This is the difference in the instrument's output reading for the same input value, depending on whether the input is increasing or decreasing. It's like a 'memory' effect where the past input affects the current output.
• Resolution: This is the smallest change in the input quantity that the instrument can reliably detect and indicate. It represents the smallest step or increment the instrument can measure.

Analyzing the Question Statement

The question specifically defines the term as "a measure of the change in instrument output that occurs when the quantity being measured changes by a given amount." This definition directly matches the concept of Sensitivity, which quantifies the relationship between the change in output and the change in the measured input.

Conclusion

Based on the definitions, Sensitivity is the characteristic that measures the change in instrument output relative to a change in the quantity being measured. Therefore, it is the correct answer.