MTS Systems LevelLimit Level Plus, Руководство по эксплуатации

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Level Plus
®
LevelLimit
®
Operation Manual
I 19 I
7.6 Grounding
7.6.1 Safety grounding
Warning:
Grounding the transmitter through a threaded conduit connection
does not meet the requirements as a grounding of the sensor for
safety.
There are two methods to provide an earth ground connection to
the earth ground of the electronics. Either method must result in a
resistance of less than 1
Ω .
• Run an earth ground through the conduit and connect directly to the
earth ground lug inside the housing.
• Run an earth ground directly to the ground lug on the outside of the
housing.
7.6.2 Shield grounding
Warning:
The shield ground does not meet the requirements as grounding of
the sensor for safety.
Immunity performance of the sensor from external sources of
surge, burst, RF, radiated emissions and other noise is dependent
on a proper ground for the shield of the communications cable.
The communications cable shield should be of a braided type and
connected to the internal ground lug of the sensor housing.
Runs in a continuous metallic conduit
When installed inside a dedicated continuous metallic conduit,
the conduit provides a level of shielding protection from external
interference and a level of ground to the sensor housing. In this case
a foil type shielded cable with a drain wire connected to the internal
ground lug may be sufficient. Sharing of the metallic conduit with
other cables will result in loss of effective shielding performance of
the communication cable and possible degradation in performance
of the sensor. In this case a braided type shielded cable connected to
the sensor internal ground lug would be recommended. In all cases
paralleling the communications cable with any noise generating cable
inside of a conduit or with noise generating cables in close proximity
to the conduit may degrade the performance of the sensor.
Runs without a conduit
In some rare applications, or where safety may not be required, a
metallic conduit may not exist. The communications cable shield
should be of a braided type and connected to the internal ground
lug of the sensor housing. Alternatively a safety approved EMC
Cable Gland can be used for grounding the shield. Contact MTS for
information before using one of these cable glands.
NEC
Undesirable currents (ground loops) is a violation of the NEC and is a
safety hazard.
7.7 Safety barriers
Refer to Table 4 for entity parameters and Table 5 for example safety
barriers
Entity parameters
Digital supply
(1 per LT)
Ui = 28 VDC
Ii = 100 mA
Ci = 0.0 µF
Li = O mH
Pi = 700 mW
Digital communication
(2 per LT)
Ui = 8.6 VDC
Ii = 10 mA
Ci = 0.0 µF
Li = 0.0 mH
Pi = 21.5 mW
Digital I/O
(1 per LT)
Ui = 28 VDC
Ii = 50 mA
Ci = 0.083 µF
Li = 8.5 mH
Pi = 350 mW
R = 666 Ohm
Table 4: Safety barrier entity parameter references
Table 5: Safety barrier entity parameter references
Supplier Stahl Stahl Stahl
Type
9001/01-280-
100-101 9001/01-086-
010-101 9001/01-280-
050-101
Maximum
voltage
28 VDC 8.6 VDC 28 VDC
Maximum
current
(each channel)
100 mA 10 mA 50 mA
Maximum
power
(each channel)
700 mW 21.5 mW 350 mW
Number of
channels
1 1 1
Interface
Modbus Modbus Digital I/O