D
OCUMENT
301900,
R
EVISION
D
E
PI
S
ENSOR
U
SER
G
UIDE
47
Class A, EN 50082-2) of the European Community. If grounding the cable
shield at both ends with long cable results in excess noise in the instrument,
the cable shields can be disconnected from the PGP connection (Pin U) at
the EpiSensor end. This may be required if significant current flows in the
shield between the two grounds. This may result in better system noise
performance. However, Kinemetrics cannot be responsible for any EMI/RFI
emissions that may occur due to this change in the cabling. The EpiSensor
should still be grounded using the grounding stud on the flange.
If changing the cabling does not solve the problem, the case grounds can be
reconnected to the EpiSensor and the EpiSensor can be isolated. To isolate
the EpiSensor, place the mounting feet on isolation washers, do not connect
the case ground strap, and use an insulating washer between the mounting
nut and the mounting bracket.
While this procedure may improve noise performance, leaving the
EpiSensor case ungrounded greatly degrades its ability to survive lightning
induced transients and can lead to a safety hazard if the location has poor
AC wiring.
A hybrid ground connection can also be used:
1. Ground the EpiSensor with the grounding strap.
2. Open the connector at the EpiSensor end of the cable.
3. Connect the cable shields and the PGP wire to one side
of a 0.1
(
F, 200 V film capacitor.
4. Connect the other side of the capacitor to the EpiSensor’s PGP
connection (Pin U).
5. Cover the wire and the capacitor with shrink tubing.
This connection can still result in a safety hazard but it does give the
EpiSensor a low impedance path for lightning induced transients.
Note:
This technique provides a single point ground for low frequency
signals at the recorder end of the cable, but at high frequencies the
capacitor conducts, providing an effective AC ground for EMI/RFI
signals.
WARNING!
Potential lethal voltages
. In these configurations, potentially
lethal voltages can exist between the conductors on the cable or the exposed
metal parts of the EpiSensor. These occur due to differences in ground
potential between the location of the recorder and the location of the
EpiSensor. Faulty electrical wiring returning large currents to ground
normally causes these differences
. It is the user's responsibility to ensure
that hazardous conditions are not created and that all local electrical safety
regulations are observed.
!
