When multiple current interrupters are employed on a
pipeline, their internal clocks must be synchronized in order to
guarantee “in-phase” current switching so that accurate instant-off
potentials can be recorded.
With “non-GPS” current-interrupter units, in order
to achieve (initial) clock synchronization, all participating units have
to be brought together in one place. Furthermore, because of clock-drift
due to local temperature variations and other effects, the clocks in the
participating units can quite quickly drift out of synchronization,
which leads to “out-of-phase” current waveforms.
The ideal scenario is one in which current
interrupter units can be left in the field for indefinite periods of
time (with no external power source required) and their internal clocks
will always be synchronized with each other during critical time
periods, such as periods of repetitive current interruption (current
cycling periods).
MC Miller's GPS Current-Interrupter (the Cronos
unit) satisfies both of these “ideal-case” requirements.
The Cronos unit does not require an external power
supply, and it can run applications for years at a time using an
internal battery power source. This is possible due to the advanced
design of the Cronos unit, which results in extremely-low power
consumption, even when the unit is tracking GPS satellites.
