A system comprising: an energy storage device coupled to a measurement circuit configured to measure an electrical parameter; a switch-mode power converter coupled to the energy storage device, the switch-mode power converter being configured to receive power at an input terminal; a first switch coupled to the switch-mode power converter configured to couple power to the input terminal of the switch-mode power converter to power on the switch-mode power converter; and a second switch coupled to an output terminal of the switch-mode power converter, wherein when the switch-mode power converter is powered on, the switch-mode power converter is configured to charge the energy storage device; characterised by the measurement circuit; a microprocessor control circuit coupled to both an input of the first switch and an input of the second switch, wherein the microprocessor control circuit is configured to provide control signals to the first switch and the second switch, respectively, to both power off the switch-mode power converter by causing the first switch to disconnect power supplied to the switch-mode power converter and at the same time, prevent the switch-mode power converter from draining power from the energy storage device by causing the second switch to decouple the switch-mode power converter from the energy storage device, wherein the microprocessor control circuit is further configured to provide timing signals to the measurement circuit to cause the measurement circuit to measure the electrical parameter while the first switch has disconnected power from the switch-mode power converter and the second switch has decoupled the switch-mode power converter from the energy storage device, and wherein the energy storage device is configured to power the measurement circuit when the measurement circuit is measuring the electrical parameter. an energy storage device coupled to a measurement circuit configured to measure an electrical parameter; a switch-mode power converter coupled to the energy storage device, the switch-mode power converter being configured to receive power at an input terminal; a first switch coupled to the switch-mode power converter configured to couple power to the input terminal of the switch-mode power converter to power on the switch-mode power converter; and a second switch coupled to an output terminal of the switch-mode power converter, wherein when the switch-mode power converter is powered on, the switch-mode power converter is configured to charge the energy storage device; characterised by the measurement circuit; a microprocessor control circuit coupled to both an input of the first switch and an input of the second switch, wherein the microprocessor control circuit is configured to provide control signals to the first switch and the second switch, respectively, to both power off the switch-mode power converter by causing the first switch to disconnect power supplied to the switch-mode power converter and at the same time, prevent the switch-mode power converter from draining power from the energy storage device by causing the second switch to decouple the switch-mode power converter from the energy storage device, wherein the microprocessor control circuit is further configured to provide timing signals to the measurement circuit to cause the measurement circuit to measure the electrical parameter while the first switch has disconnected power from the switch-mode power converter and the second switch has decoupled the switch-mode power converter from the energy storage device, and wherein the energy storage device is configured to power the measurement circuit when the measurement circuit is measuring the electrical parameter.