What are the “Tacho” inputs for on the EMU-1?

Created onApril 21, 2020

Updated onJuly 7, 2023

“Tacho” inputs are designed to be connected to existing Tacho signals from either the Alternator (“W”, ”R” or “AC”) terminal, an inductive Tach sender, an ignition coil or – a hall-effect Tacho sender. The Toolkit allows the user to define “Ratio” or the number of “Pulses Per Revolution” that the selected Tacho signal will generate for each “Tacho” input. This ratio is usually referred to as the Pulses Per Revolution (PPR) and is normally supplied in the engine manual.

For an Alternator (“W”. “R” or “AC”) terminal connection it can be calculated from: PPR = (Crank pulley diameter / Alternator pulley diameter) × (No.of poles in Alternator / 2)

For an inductive sender it is derived from the number of teeth on the flywheel: PPR = No.of teeth on flywheel

For an ignition coil it can normally be calculated from PPR = (No.of cylinders × 2) / (No.of strokes × No.of ignition coils)

The engine manufacturer will usually supply this ratio so it should not need to be calculated.

The EMU-1 has the ability to automatically adjust to the input Tacho signal so the sender type does not need to be configured. However, currently only Alternator (“W”, ”R” or “AC”) and inductive Tach sender signals are sensed correctly by the EMU-1. If you wish to use an ignition coil signal with an EMU-1 please contact Actisense Technical Support so your request can be processed.

For more information on NMEA 2000 and how it works, please download our free guide to NMEA 2000 networking here: https://actisense.com/complete-guide-to-building-an-nmea-2000-network/

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What are the “Tacho” inputs for on the EMU-1?