In accordance with MIL-E-24021F (now MIL-PRF-24021), DARE external aircraft electrical power monitors sense the output characteristics of 115V, 400 Hz ground power and protect aircraft electrical systems from over or under voltage, over or under frequency, or improper phase rotation utilizing a completely solid-state design.
If the monitor determines the condition of the 115V 400 Hz power source is out of specification or unacceptable in terms of MIL-STD-704, the output of the power monitor is de-energized. The output of the power monitor controls the coil circuit of the aircraft’s AC contactor. When the coil circuit to the aircraft’s AC contactor is de-energized, the power monitor prevents power outside the limits of MIL-E-24021 (MIL-PRF-24021) from being applied to equipment in the aircraft.
As specified in MIL-PRF-24021K, there are three external aircraft power monitor models:
| Part Number | Type of Monitor | Superseded Part Number |
|---|---|---|
| M24021-3 | AC monitor for use with DC operated contactors, including source of DC for contactor | M24021-2 |
| M24021-5 | AC monitor for use with AC or DC operated contactors (but not including source of AC or DC for contactor) | M24021-4 |
| M24021-6 | DC monitor | N/A |
DARE offers each type of power monitor, and all of DARE’s external aircraft power monitors are hermetically sealed and encapsulated for immunity to shock and vibration.
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