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Understanding Magnetic Pickup (MPU) and RPM Monitoring in Enbase

Learn how Enbase uses a Magnetic Pickup signal to calculate engine RPM, why flywheel tooth count matters, and what to review when RPM appears incorrect.

A Magnetic Pickup, commonly called an MPU, is a sensor that can be used to determine engine speed. Enbase can use the pulse signal from an MPU to calculate and display engine RPM.

How Does an MPU Measure Engine Speed?

An MPU detects the teeth of a rotating flywheel. Each passing tooth generates a voltage pulse. Enbase counts the pulses over time and uses the configured number of pulses per revolution to calculate RPM.

Why Does the Flywheel Tooth Count Matter?

The MPU signal tells Enbase how many pulses are occurring, but Enbase also needs to know how many flywheel teeth, or pulses per revolution, correspond to one full engine revolution.

If the configured tooth count is incorrect, the RPM shown in Enbase will also be incorrect. For Compressor Control Panel installations, the Driver Speed Tag should be configured using the correct flywheel tooth count.

How Is the MPU Signal Represented in Enbase?

MPU signals are handled as frequency based inputs. Enbase can convert the pulse frequency into an RPM value that is represented as a Tag and can then be monitored, trended, or used by other configured functions.

Can Enbase Get RPM Without an MPU?

In some installations, engine speed can be received directly from an engine controller through a supported communication method such as Modbus or CAN instead of using a dedicated MPU.

Whether this option is available depends on the engine controller and the configuration of the Enbase installation. Contact Enbase Support if you need to confirm how RPM is being obtained for a specific asset.

What If Enbase Is Reporting Incorrect RPM?

If the RPM value does not look correct, review the following before making configuration changes:

  • The RPM value shown in Enbase compared with the expected engine speed
  • The Driver Speed Tag configuration and configured flywheel tooth count
  • The Scan Status for the RPM related Tag
  • Whether the MPU signal is stable or intermittent
  • Any recent sensor, wiring, engine, or controller changes

The Enbase Compressor Control Panel troubleshooting guide also identifies secure MPU connections and correct flywheel tooth scaling as key checks when reported RPM is inaccurate.

If the problem continues, contact Enbase Support and provide the asset name, expected RPM, RPM shown in Enbase, and any related Scan Status or error information.