Abstract:
A self-referencing sensing and control apparatus which may be used advantageously in any industrial installation in which an A. C. powered device, such as the down-hole motor in a submersible pumping system or a plunger relay, is remotely located and in which it is desired (i) to monitor certain parameters, such as temperature and pressure, and/or (ii) to control certain operational functions, such as the state of flow valves and latching means, at the remote site. The power cable used to carry A. C. power to the remotely operating device is also used to carry instrumentation and control signals from local control and readout equipment to an instrumentation package installed at the remote site. The present invention comprises switching means to selectively couple and decouple one or more sensors (or control means) in the instrumentation package to and from the A. C. operating device and the power cable, thereby permitting high voltage testing of the A. C.