Measurement circuits

Measurement circuits are designed to determine the value of an electrical or physical quantity and present it in a usable form. Where a power or control circuit acts on a signal, a measurement circuit observes one: it senses a voltage, current, frequency, temperature or other quantity and converts it into a reading on a meter or display, or into a signal another instrument can record. These circuits are the basis of test equipment and instrumentation, and they are essential for building, troubleshooting and characterizing other electronics.

Many measurement circuits revolve around turning the quantity of interest into a proportional voltage that is easy to display. A digital voltmeter, for example, measures voltage directly, while sensing circuits convert current, temperature or other variables into a voltage first. Frequency counters and beat-frequency indicators measure how often a signal repeats, and detectors flag specific conditions, such as the presence of an alternating-current field or the loss of an expected pulse. Battery-level meters and similar circuits translate a measured value into a simple indication a user can read at a glance.

Closely related are signal sources used in testing, such as function generators that produce triangle, square and sine waveforms, and low-frequency sine-wave generators. These supply known signals so that a circuit's response can be measured. Designing measurement and instrumentation circuits emphasizes accuracy, stability, low noise and calibration, since errors in the circuit appear directly as errors in the reading. Collections of measurement circuits include meters, counters, detectors and generators useful for the electronics workbench.

Frequently asked questions

What do measurement circuits do?

They sense an electrical or physical quantity and convert it into a reading, display or recordable signal for testing and instrumentation.

How is a varying quantity usually measured?

It is commonly converted into a proportional voltage, which is then displayed directly or processed further.

Why are function generators grouped with measurement circuits?

They supply known test waveforms, such as sine, square and triangle, so that a circuit's response can be measured.