MD7ST
EM-8057 Rev.4 P. 4 / 4
■
CONNECTION DIAGRAM
•
Specify ‘Loop disconnect fuse’ type when multiple transmitters are connected to single power bus.
•
Loop disconnect fuse is used to separate a transmitter loop from the power bus when it fails in the shortcircuit mode.
5
2
8
4
1
(SHLD)
DIN RAIL
DIN RAIL
ADAPTOR
Current Loop Supply
4 – 20mA
Transmitter
Field-mount
Surge Protector
(model: MD6x)
+
–
+
–
FG
Protected Side
Crossover Wire
Surge Side
*
1. Oxide film on the surface of an aluminium rail may lower the electric conductivity between this module and the ground.
Use a steel or copper rail.
*
2. Be sure to ground the DIN rail. Recommended grounding resistance ≤100
Ω
*
3. Cross-wire between the DIN rail and the metal housing of the protected device to equalize the earth potential.
Ground only the surge protector when the protected device has no ground terminal.
*
4. Shield wiring method is an example. Proceed according to the system requirements.
*
4
*
2
*
1
*
3
WIRING INSTRUCTIONS
■
EURO TERMINAL
Torque: 0.3 N·m
Applicable wire size: 0.2 – 2.5 mm
2
Stripped length: 8 mm
MAINTENANCE
Check surge protectors periodically. Many cases of light-
ning are ignored, and even lightning at a far distance often
causes inductive surges.
We recommend that you check your surge protector about
twice a year, before and after the rainy season. Check
whenever you experience a strong lightning occurrence.
Checking procedure is explained in the following:
■
CHECKING
WIRING
1) Make sure that wiring is done as instructed in the con-
nection diagram.
2) Make sure that the DIN rail is connected to the metal
enclosure of protected device.
3) Make sure that the surge protector is securely attached
to the DIN rail, and that the rail is grounded to earth.
■
DISCHARGE ELEMENT
1) Remove all wiring connected to the surge protector when
you test the module.
2) Check resistance across the terminals indicated in Table
2 on the high resistance range of multimeter and confirm
no conduction. The tester should show 10 MΩ or greater.
3) Confirm conduction across the same terminals with a 500
V DC 1000 MΩ insulation tester. The tester should show
20 MΩ or less.
With loop disconnect fuse option, confirm conduction
across the following terminals on the high resistance
range of multimeter. The tester should show 15 Ω or less.
1 – 4, 2 – 5
Polarity of the insulation tester does not matter.
4) If any of the above tests shows negative, replace the
surge protector.
Table 2.
TERM.
MODEL
MD7ST-xFF MD7ST-xFG MD7ST-xGF MD7ST-xGG
4 – 5
Yes
Yes
Yes
Yes
4 – 8
No
Yes
Yes
Yes
5 – 8
No
Yes
Yes
Yes
8 – 5
No
No
Yes
Yes
5 – DIN rail
Yes
Yes
No
Yes
8 – DIN rail
Yes
No
Yes
No
Note 1: Apply (+) voltage of the multimeter to the terminal
number indicated on the left side.
Note 2: Polarity does not matter for the insulation tester.
056 222 38 18
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AG
