The DP243 is used to measure differential expansion (relative axial expansion) between the steam turbine rotor and the casing.

Structurally, it consists of a mechanical pendulum assembly and a magnetic sensing probe (magnetic follower).

Its primary function is to measure the rotor collar (MBS) of the high-pressure cylinder, capturing the difference in thermal expansion between the rotor and casing during startup, shutdown, and load changes. It outputs a signal to the unit's protection system; if differential expansion exceeds limits, it triggers a turbine trip.

It is widely used in turbine monitoring systems for nuclear power plants and large-scale thermal power units.

However, the following points should be noted during field application:

A specific safe clearance range must be maintained between the probe's magnetic follower and the rotor's measurement collar; if the gap is too small, friction between rotating and stationary parts may occur, while an excessively large gap may exceed the measurement range. Please refer to the DP243 technical manual for details.

The DP243 pendulum differential expansion sensor is distinct from conventional eddy-current axial displacement probes; it utilizes a mechanical sensing structure suitable for long-stroke differential expansion measurements and offers excellent performance in low-frequency, static displacement measurement.

It is frequently paired with Vibro-Meter (Meggitt) 2000 series and VM600 condition monitoring and protection systems, as well as TSI (Turbine Supervisory Instrumentation) safety monitoring platforms for nuclear power turbines.

Warning: Potential for confusion

Some market literature refers to it simply as the "DP243 probe." Do not confuse it with PV series vibration sensors (e.g., PV685, VE210) or TQ series eddy-current displacement probes; the DP243 is used exclusively for differential expansion measurement and does not measure shaft vibration or axial displacement.