Measurement and Instrumentation Flashcards

Hysteresis error in a measurement system means the output depends on:

Answer: The direction from which the input is approached

Hysteresis causes different output readings for the same input depending on whether the input is increasing or decreasing.

Which instrument is best suited for measuring very low resistances (below 1 Ω) accurately?

Answer: Kelvin double bridge

The Kelvin double bridge eliminates the error due to lead and contact resistance by using a second set of ratio arms, making it ideal for milliohm measurements.

In a spectrum analyzer, the x-axis represents:

Answer: Frequency

A spectrum analyzer displays signal amplitude (power or voltage) as a function of frequency, unlike an oscilloscope which uses time on the x-axis.

The accuracy of an instrument is best defined as:

Answer: The closeness of the measured value to the true value

Accuracy is the degree of conformity between the instrument's reading and the true value of the quantity being measured.

A power factor meter used in a single-phase circuit has how many current coils and voltage coils?

Answer: One current coil and two voltage coils

A single-phase power factor meter has one current coil carrying load current and two crossed voltage coils — one in series with a resistor and one in series with an inductor.

When a voltmeter of 1000 Ω/V sensitivity is set to the 100 V range, its internal resistance is:

Answer: 100,000 Ω

Internal resistance = sensitivity × range = 1000 Ω/V × 100 V = 100,000 Ω (100 kΩ).

The term 'dead zone' in an instrument refers to:

Answer: The range of input values that produce no change in output

The dead zone (or dead band) is the largest range of input change that fails to produce any detectable change in the instrument's output.