Appendix 8 Concerning Noise Countermeasures
A17
Appendix
2nd. Blocking Noise from External Sources
Keep signal lines away from noise sources
Keep input signal lines (of the thermocouple) away from wiring that is a noise source
(such as power lines, etc.), and make any permanent installation with as much separa-
tion as possible; for example, by running wires through a separate duct.
Use shielded twisted pair wiring
It is effective to use shielded twisted pairs for the input signal lines (of the thermocouple).
Twisted pairs are effective for preventing electromagnetic induction, and shielded wires
are effective for preventing electrostatic induction.
The shielded wires should basically be grounded on the signal source side. If it is not
possible to connect the signal source to ground, connect it to the chassis GND on the
8430-20. Note that doing so has no effect if the 8430-20 is not itself connected to ground
through the three-prong power cord, etc.
Shielded twisted pair wires for the thermocouple can be obtained from thermocouple
manufacturers.
Normal Mode Noise Countermeasures
Power Supply Line
Electromagnetic
Coupling
Electrostatic
Coupling
Inverter or Com-
mercial Power
Supply
Shielded
Twisted Pair
Wires
The shielding for the signal lines
is grounded on the signal side
Keep the signal lines (of the thermocouple) away from wiring that is a noise source
(such as power lines, etc.). It is also possible to shield the signal lines from elec-
trostatic coupling and to block noise by grounding the shield.
Device being
Tested
HiLogger
Thermocouple
If the signal side is not grounded or if it is grounded inadequately, connect the HiLog-
ger to ground. Also ground the shielding for the signal wires on the HiLogger side se-
curely.
Ground Wire
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