J.P. Instruments EDM 960 Twin Primary Installation Manual - Manual (Page 19)

FAA Approved Installation Manual for the EDM-960 system Report No 909
Primary Engine Data Management System Page 19 of 46 Rev D
Date 2-6-2014
28. Fuel Level Interface Installation
The EDM-960 has the capability to interface to 4 tanks in the aircraft’s fuel level system. This is done by connecting
the DAU directly to the senders or in some cases to the aircraft’s fuel sender signal conditioner, for example the
Pennycap system which converts capacitance (frequency) to a voltage output, typically found in Cessna Twins. The
DAU has the capability to process signals from two types of sender signals: Resistive output, Voltage output. JPI
provides the appropriate interface hardware (the P5 harness and any associated signal conditioners) based on
information you provided when your order was placed. Once installation is completed, you will perform a fuel level
calibration. The EDM-960 stores this calibration internally. NOTE: The fuel quantity function will not be available until
this calibration has been performed successfully.
28.1 Resistive Output Type Sender System
Locate the wires that run between the existing ships fuel gauges and the senders and disconnect them at the senders.
For tanks that have more than one sender, the wiring between the senders must be retained. Make sure the senders
do not have voltage on them before connecting to the EDM. Connect the EDM to the senders using the wire pairs
coming from the signal conditioner (PN 790802) P7 as shown below. Note that one pair is for MAIN and the other is for
AUX. Connect the ‘SIG’ wire to the senders signal terminal (typically the center stud) and the ‘GND’ wire to the closest
ground terminal near or on that sender.
28.2 Voltage Output Type Sender System
Voltage output type systems usually have a convertor box. This is typical with the ‘Pennycap’ brand capacitive sender
system. The Pennycap convertor box measures sender capacitance and converts it to a DC voltage output signal for
the aircrafts fuel level gauge. Connect the EDM to the Pennycap converter box using the wire pairs coming from the
signal conditioner (PN 791802). In some cases the Pennycap convertor box alternately monitors two tanks per wing
controlled by cockpit selector switch positions. This is typical for Cessna twins having 4 selectable tanks. The EDM can
interface to this system with the addition of the dashed interface hardware (PN 790810) shown below. NOTE: This
drawing is accurate for most models of the Pennycap system; however it is the installer’s responsibility to verify proper
connections to the Pennycap output signal. Note: The original ships gauge and all gauge selector switches and related
annunciate lights must remain in the aircraft. The gauge could be mounted behind the panel if desired.