Which type of meter movement is most commonly used for a "strip-chart" recorder?

The most commonly used type of meter movement for a "strip-chart" recorder is the plunger movement. This type of movement is suitable for applications that require a continuous recording of data over time, such as in strip-chart recorders that track variables like temperature, pressure, or voltage.

Plunger movements operate based on the principle of mechanical displacement, where the movement of a plunger corresponds to the variation in the measured parameter. As the plunger moves, it can drive a pen or stylus across a moving strip of paper, allowing for a visual representation of the data collected over time. This method is effective for providing a clear, ongoing graph of readings, which is particularly useful in applications requiring historical data tracking.

While the other options—digital, galvanometer, and analog movements—are relevant in different contexts of measuring instruments, they do not align as closely with the functional requirements of strip-chart recorders. Digital meters provide numerical readings but lack continuous graphical representation, galvanometers are typically used for rapid response and precision measurements rather than continuous recording, and analog movements could represent data but do not utilize the strip-chart mechanism as efficiently as plunger movements do.