LEMO 8-Pin Input Wiring for FE-1408 and FE-1410
Note: The wiring of the LEMO plug is only correct for current 2018 and newer Hummingbird units
LEMO Pin Numbers: Looking from the front of the unit or rear of plug
LEMO Receptacle Labelled
| Pin | Description | Symbol | Color |
| 1 | Amplifier Input - | N, -ve input | Blue |
| 2 | Excitation Sense/Reference + | R+, Sense + | Green White |
| 3 | Excitation Sense/Reference - | R-, Sense - | Brown White |
| 4 | Excitation Supply | S+, Excitation + | Orange |
| 5 | Analogue Ground | GND, Analogue Ground | Brown |
| 6 | Excitation Supply - | S-, Excitation - | Orange White |
| 7 | 1/4 Bridge Completion Resistor | QTR, 1/4 Bridge | Green |
| 8 | Amplifier Input | P, +ve input | Blue White |
A number of different sensor wiring configurations are possible with this connector, these are listed below.
- 1/4 Bridge Strain
- 1/2 Bridge Strain
- Full Bridge Strain
- Single Ended and Differential Charge
- Dynamic Strain
- IEPE
- Voltage
NOTE: the Sense+ and Sense- pins should be connected as close to the gauge being measured as possible (to where the relevant Power or Ground pins are connected); this is not shown in the diagrams below for reasons of clarity.
1/4 Bridge Strain (3 wire method)
The 3 wire method of wiring or ¼ bridge provides better balance and noise performance than the more traditional 2-wire method (see below). In the configuration shown the internal shunt calibration resistor(s) is actually shunting the completion resistor. Whilst this does not affect the value of the calibration the sign of it is affected.
1/4 Bridge Strain (2 wire method)
The 2 wire method of wiring or ¼ bridge provides worse balance and noise performance than the 3-wire method described above. However if the strain gauge is close to the Dragonfly then it does provide an easier wiring method for similar performance. For long distances between the gauge and the Dragonfly the 3 wire method is highly recommended.
In the configuration shown the internal shunt cal resistor(s) is actually shunting the completion resistor. Whilst this does not affect the value of the calibration the sign of it is affected.
1/2 Bridge Strain
In the configuration shown the internal shunt calibration resistor(s) only operates on gauge
Full Bridge Strain
Full bridge strain only utilizes the power and amplifier inputs of the Dragonfly. The shunt can still be used but only operates on gauge 1.
Dynamic Strain
Dynamic strain provides an AC only signal from a single strain gauge. The gauge is energized by an internal constant current generator which is fully programmable.
For situations where the dc component of strain is not required this configuration provides a much simpler wiring model than a bridge configuration. It is also simpler to use operationally.
Voltage / IEPE Measurements
Voltage Mode provides AC / DC and Differential / Single Ended signals from a suitably equipped sensors, there is no internal excitation in this mode.
Charge Measurements
Single Ended Charge connects the (-)VE to ground providing a single ended connection.
DIFF Charge Mode provides an AC only signal from a differential charge sensor.
