Abstract: A circuit and method for measuring the switch opening time, in cycles, of a medium voltage air circuit breaker. The circuit senses DC current feeding the trip coil in the circuit breaker. The timer starts a predetermined programmable time interval after the DC current starts flowing in the breaker trip coil circuit. The timer stops when the DC current stops flowing in the breaker trip coil circuit. The programmable time interval is a delay between the opening of the breaker's primary contacts and the opening of the trip coil circuit switch, and is used to determine the circuit breaker opening time from the starting and stopping of the timer. The timing device does not require connection to the circuit breaker's main power contacts.