Which type of meters operate from their own power sources?

The type of meters that operate from their own power sources are known as self-excited meters. These meters generate the necessary electrical energy required for their operation independently, rather than relying on an external power source. This characteristic allows self-excited meters to be more versatile in various applications, as they can function in environments where external power might be unavailable or unstable.

In the context of measuring instruments, self-excited meters typically incorporate a mechanism that converts mechanical energy into electrical energy, ensuring they can provide readings without needing an external power supply. This makes them particularly useful in scenarios where portability and independence from external power sources are desired.

Other types of meters, such as passive, analog, and active meters, have different operational characteristics. Passive meters typically require an external power source to function, while analog meters (which can be active or passive) often rely on external voltage for their operation. Active meters, similar to self-excited meters, can have internal power sources designed for specific measurements; however, they are not categorized solely as self-excited. Understanding these distinctions helps clarify why self-excited meters are identified as those that operate from their own power sources.