Collar location in cased hole for depth correction
The Casing Collar Locator (CCL41) measures positioning in cased holes by responding to the changes in metal volume. The CCL detector consists of a coil and four magnets. The four magnets are installed in pairs at the upper and lower ends respectively so that the coil is in a constant magnetic field. When the tool passes a collar, the magnetic flux is disturbed and an electric signal is generated. The signal is then amplified and converted to frequency, which is then counted in MCU. When the telemetry cartridge polls, the count is sent to telemetry for encoding and then to the surface.