I'm sure I'm missing it, but where does this say it needs to be a 12 volt vs a 5 volt square wave input? What I see is this:
“F” – Frequency or a Digital Speed Input – Designed for a digital voltage input from a speed/rotation sensor. A Hall-Effect sensor is the common sensor used. Voltage range can be 4.5 to 24 volts. With that it seems a 5V input would work. Right?