A high-temperature low-cost rotational speed transducer for oil-well telemetry

The high-temperature environment of an oil-well requires reliable downhole instrumentation, typically based on simple and robust circuits, low power consumption and smart measurement algorithms. In this paper, we present an electronic design and measurement methodology for a simple, low-cost rotational speed transducer, optimized for downhole spinner-flowmeter applications and multichannel telemetry. We have developed and experimentally evaluated an effective algorithm for direction-sensitive rotational speed measurement, which combines quadrature pulse decoding with a dependant count method. The algorithm employs temperature compensation techniques, making it suitable for low-cost high-temperature circuit designs. Our preliminary results confirm reliable operation of the transducer, targeted at high-temperature, short-term oil-well logging applications.