Telemetry circuit for remote measurement - uses separate AC and current sources to reduce capacitance effects over long cables

摘要

A telemetery circuit with an constant amplitude a.c. source (3) connected in series with the measurement transducer (1) e.g. an optical transducer, through a long wire (10). The transducer is also connected to a current source (4) through wire (5). The two wires together with the metalic screen (6) make the connection cable. The screen is connected to the current feed back lead between the voltage source and an indicating instrument. An alternative circuit si given with a voltage converter connected to a secondary winding of a transformer and the primary winding connected to the current converter with the wires (5, 10) connected to the inner side of each winding. The a.c. source and current converter are mounted adjacent to each other in a screened box.