Connecting analogue inputs to the EMU-1
Gauge Input Connections
There are six Gauge inputs which are designed to be connected to existing engine senders (resistive type) either with or without the gauge connected. In the case where no gauge is connected the EMU-1 automatically provides a feed to the sender. A dual station sender must always have two gauges connected to it: the EMU-1 cannot replace one or both of those gauges. If it is required to remove one or both gauges, the dual station sender will need to be replaced with a single station sender.
Insulated Terminal Sender with Gauge (G1 Input):
- The gauge power connection is connected to the same positive voltage supply as the EMU-1.
- The gauge ground connection is connected to the same ground as the EMU-1.
- The gauge signal connection is connected to the sender signal line.
- The sender return connection is connected to the same ground as the EMU-1.
- The EMU-1 Gauge input is connected to the gauge signal line, typically with a cable run that does not exceed 2 metres with a minimum 0.5mm wire diameter (24 AWG).
Insulated Terminal Sender without Gauge (G2 Input):
- The senders return connection is connected to the same ground as the EMU-1.
- The EMU-1 Gauge input is connected to the sender signal line, typically with a cable run that does not exceed 2 metres with a minimum 0.5mm wire diameter (24 AWG).
Standard Grounded Sender without Gauge (G3 Input):
- The sender chassis is connected to the same ground as the EMU-1.
- The EMU-1 Gauge input is connected to the sender signal line, typically with a cable run that does not exceed 2 metres with a minimum 0.5mm wire diameter (24 AWG).
Standard Grounded Sender with Gauge (G4 Input):
- The gauge power connection is connected to the same positive voltage supply as the EMU-1.
- The gauge ground connection is connected to the same ground as the EMU-1.
- The gauge signal connection is connected to the sender signal line.
- The sender chassis is connected to the same ground as the EMU-1.
- The EMU-1 Gauge input is connected to the gauge signal line, typically with a cable run that does not exceed 2 metres with a minimum 0.5mm wire diameter (24 AWG).
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Alarm inputs
There are four Alarm inputs which are designed to be connected to existing alarm type switches. The EMU-1 can be used with or without the alarm indicator (e.g. lamp or buzzer) connected. If there is no alarm indicator, a suitable resistor can be used in its place.
For 12 V supplies it is recommended to use a 1 kΩ, ¼ W resistor, for 24 V supplies it is recommended to use a 1 kΩ, 1 W resistor. Some alarm switches are incorporated into their relevant sender and are also suitable to connect to the EMU-1.
There are several different combinations of switch type and wiring method that the EMU-1 Alarm inputs are compatible with.
Supported Switch and Installation Types
- Normally Open switches
- Normally Closed switches
- Active High (see Figure 8 Examples A3 and A4).
- Active Low (see Figure 8 Examples A1 and A2).
Critical Circuit Requirements
- The switch circuits positive supply is the same as the supply used to power the EMU-1.
- The switch circuits negative supply (ground) is the same as the EMU-1 power ground.
- The switch circuit has a load (e.g. buzzer, lamp or resistor) in series with the switch between the positive supply and ground.
- The EMU-1 Alarm input is connected between the switch and the load (e.g. buzzer, lamp or resistor).
Additional Information
- If the EMU-1 is connected at the switch, the cable run should not typically exceed 2 metres.
- If the EMU-1 is connected at the buzzer or lamp, the cable run should not typically exceed 2 metres.
- If replacing the buzzer or lamp with a resistor this should be done as near to the EMU-1 as possible, in this case the cable run should not typically exceed 2 metres.
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Tach inputs
There are two Tacho inputs which are designed to be connected to existing engine senders either with or without the gauge connected. The Tacho inputs must be calibrated in the configuration tool. The Pulses per Revolution (PPR) must be entered to allow the correct RPM to be calculated by the EMU-1.
There are several different sender options that can be used to generate NMEA 2000 RPM data. Each supported type is listed below along with the information required to configure the input using the configuration tool.
Ignition Coil
- Connect the negative connection of the ignition coil to the positive Tacho input of the EMU-1.
- The negative Tacho input of the EMU-1 should be left unconnected.
- For calibration the PPR or the number of cylinders will need to be entered in the configuration tool.
Alternator
- Connect the Tacho (AC Tap) or ‘W’ connection of the alternator to the positive Tacho input of the EMU-1.
- The negative Tacho input of the EMU-1 should be left unconnected.
- For calibration the PPR or the number of poles and the pulley ratio will need to be entered in the configuration tool.
Hall Effect and Electronic Pulse Senders
- Connect the signal line of the sender to the positive Tacho input on the EMU-1.
- The negative Tacho input of the EMU-1 should be left unconnected.
- For calibration the PPR or the number of teeth on the fly wheel will need to be entered in the configuration tool
Inductive Senders
- Connect the positive signal line from the sender to the positive Tacho input of the EMU-1.
- Connect the negative signal line from the sender to the negative Tacho input of the EMU-1.
- If the negative signal line is not available, the negative Tacho input of the EMU-1 should be left unconnected, and the sender should be connected to the same ground as the EMU-1.
- For calibration the PPR or the number of teeth on the fly wheel will need to be entered in the configuration tool.
How do I calculate Tacho PPR
The EMU-1 configuration tool allows the “ratio” to be configured. This ratio is usually referred to as the PPR (Pulses Per Revolution). The engine manufacturer will usually be able to supply this ratio so it should not need to be calculated.
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)
