| 摘要 |
A humidity resistant device (24 and 78) for reading a meter having multiple dial faces and a rotatable meter hand (17-18) and axle (19) for each dial face that includes for each dial face (a) a plate (16) disposed between the dial face and the meter hand; (b) an array of spaced apart excitable electrodes (11-1 through 11-10) on one surface of the plate confronting the meter hand and defining an array about a center portion that includes the axle (19) of the rotatable meter hand; (c) a center electrode (12) in the center portion forming a part of a plate capacitor between each excitable electrode and the center electrode, the center electrode connected to and monitored by a receiver circuit (24), for sensing current amplitude through each such plate capacitor and spaced apart from the array of excitable electrodes and the axle (19) of the rotatable meter hand; (d) an A.C. voltage signal source (25) for placing a predetermined voltage signal on a pre-determined one of the excitable electrodes; and, (e) a D.C. reference voltage source (33) connected both to the center electrode (12), a transimpedance amplifier (44), and a guard (21), to maintain the center electrode (12) and guard (21) at essentially the same voltage. The guard (21) circumscribes and is spaced apart from both the center electrode (12) and the excitable electrodes (11-1 through 11-10) and electrically buffers the center electrode (12). |
