1. n. [Formation Evaluation]

A system for converting the measurements recorded by a wireline or measurements-while-drilling (MWD) tool into a suitable form for transmission to the surface. In the case of wireline logging, the measurements are converted into electronic pulses or analog signals that are sent up the cable. In the case of MWD, they are usually converted into an amplitude or frequency-modulated pattern of mud pulses. Some MWD tools use wirelines run inside the drillpipe. Others use wireless telemetry, in which signals are sent as electromagnetic waves through the Earth. Wireless telemetry is also used downhole to send signals from one part of an MWD tool to another.

See related terms: cartridge,  mud pulse telemetry,  sonde