An engine compression braking system having a rocker lever and reset valve assembly to operate an engine in both normal power and braking modes while effectively controlling opening and closing of the exhaust valve for compression braking. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage. The method further includes sensing, by a second sensor, a movement of the work piece relative to the sewing head. The multiple beams are then used in multiple parallel interferometric measurements.