Abstract: A monitor can be installed in the terminal block having a monitor access opening. The installed monitor allows for current measurement without having to disconnect a wire from the terminal block. Similar monitors can measure voltage, detect ground loops, and provide continuous readings of circuit parameters. Embodiments can positively hold probe tips, transmit data over wires, or transmit data wirelessly. Make-before-break monitors allow parameters to be measured without ever breaking the monitored circuit. Break-before-make monitors allow the monitored circuit to be interrupted and then reconnected with a monitor in place.