Which device can help measure electrical consumption accurately?

The voltmeter is a device designed specifically to measure the electrical potential difference in volts between two points in an electrical circuit. By determining the voltage and, when used in conjunction with other measurements such as current, it can provide insights into the power consumption of electrical devices.

While measuring voltage alone does not provide a complete picture of electrical consumption, it is essential because electrical power can be calculated using voltage and current (Power = Voltage × Current). A voltmeter is crucial when evaluating the efficiency and performance of electrical systems, making it foundational in assessing electric consumption accurately.

The other devices listed serve different functions: a manometer measures pressure, a thermometer measures temperature, and an oscilloscope is used to visualize and analyze the waveform of electrical signals. These do not directly measure electrical consumption, which is why they are not the correct choice in this context.