Identifying Integrating Type Instruments

Instruments used for measurement can be broadly classified based on how they indicate or record the measured quantity. One common classification includes indicating instruments, recording instruments, and integrating instruments.

• Indicating instruments: These instruments show the instantaneous value of the electrical quantity being measured at the moment of measurement. Examples include ammeters, voltmeters, and wattmeters. They have a pointer that moves over a graduated scale.
• Recording instruments: These instruments provide a continuous record of the quantity being measured over a period of time. They usually have a pen attached to the moving system, which traces a graph on a chart moving at a constant speed. Examples include recording voltmeters or ammeters, and some pressure recorders.
• Integrating instruments: These instruments measure the total quantity of electricity or electrical energy supplied over a specific period of time. They do not indicate the instantaneous value but rather accumulate the effect of the quantity over time.

Analyzing the Instrument Options

Let's look at the given options:

• Ammeter: An ammeter measures the electric current flowing in a circuit at a particular instant. It is an indicating instrument.
• Energy meter: An energy meter measures the total electrical energy consumed by a load over a period. Energy is the product of power and time (\(E = P \times t\)). The energy meter accumulates the power consumed over time to give a total energy reading (usually in kilowatt-hours, kWh). This perfectly fits the definition of an integrating instrument.
• Voltmeter: A voltmeter measures the potential difference between two points in a circuit at a particular instant. It is an indicating instrument.
• Pressure recording instrument: This type of instrument records the pressure over time, typically showing the pressure value at different points in time on a chart or display. While it records over time, it usually presents instantaneous pressure values over that period, acting more like a recording instrument displaying instantaneous readings rather than integrating the pressure value to provide a total quantity based on pressure accumulated over time.

Based on this analysis, the instrument that measures the total quantity accumulated over a period of time is the energy meter.

Therefore, the Energy meter is representing an integrating type instrument.