Chesapeake Black 2 Oil Pressure Gauge 80 PSIPerimeter-lighted Black dial with stylish Blue and White graphics, polished stainless steel bezel, contoured White pointer and domed glass lens.A pressure gauge operates by sending a low amperage current through the gauges meter to ground via a sending unit with variable resistance. The resistance of the sending units increase or decrease with the changes in pressure, temperature, etc...As the senders resistance varies, the amount of current allowed to