[diesel_john]

As i remember the steel pickup transducer was very stiff maybe 1/4" wide and thick. Found a photo. Looks like two semi circular chunks of piezo with a stiff collar backing it up. Loosening the thumb screw allows the piece to split. The contact area to the line needs to be paint, grease, dent, moisture etc. free. Available in most line sizes for about $60. or make your own. Charge voltages are high so a circuit to change to charge signal to a voltage signal would be good.