We're trying to use a mag pickup to drive the frequency input on a PV780. We believe we're not getting enough energy to drive the display at low speeds; we get no reading until about 4 mph. We found a zero speed Hall Effect sensor that will fit on the transmission. Will the frequency input on the PV780 read a 0.6 to 12vdc square wave signal? If not can one of the analog or digital inputs use that signal to measure a frequency?