The Model AP600 Near Bit Sub is designed to be used with the Applied Physics Model AP250 Electric Dipole System. The Near Bit Sub enables measurement of inclination and gamma count data approximately two feet behind the bit. Data is wirelessly transmitted around the downhole motor to the Electric Dipole System. Received data is decoded by the Electric Dipole electronics, where it is logged and periodically transmitted to the surface.

Inclination is sent continuously to the MWD system even while the drillstring is rotating, and tracks very closely with the inclination measurement in the MWD system located above.The Azimuthal gamma sensor in the Near Bit Sub collects gamma counts while rotating and places this data into 1 of 8 bins. System software then tabulates the counts that correspond to top and bottom bins, and sends “up/down” or “high/low” information to the MWD System so that drilling decisions can be made in real time.The 3.5 API Regular sub has four packets, one each for inclinometer, gamma, transmission electronics, and battery. The 4.5 API Regular sub has five packets, with the same contents as the 3.5 API Regular sub, but with an extra battery. Battery life is typically between 8 - 120 hours per single battery stack.