Dwyer DPM - Manual (Page 13)

Particulate Monitoring Systems
Installation & Operating Manual
Document No. 210-1003-M Page 6 ©2007
There are connections inside the control unit for the sensor coaxial cable, the power supply, relay
contacts and optional 4-20mA or RS-485 outputs. Refer to the installation drawings.
Conduit openings are provided in the bottom of the enclosure to route wiring into the enclosure.
Never drill new conduit openings in the side or top of the enclosure as a bad conduit seal may allow
water to enter the enclosure.
3.3 Grounding
Proper grounding of the control unit is essential to ensure reliable operation and operator safety.
When used as part of an approved hazardous area system two separate ground connections are
required, protective ground and intrinsic safety ground. It is not sufficient to use a single ground
connection and jumper the protective and intrinsic safety grounds inside the control unit enclosure.
CONTROL UNIT GROUNDING
• Protective earth ground must be connected to terminal #1.
• The enclosure cover must be bonded to the enclosure base with the supplied
ground bonding wire – do not remove.
• When used as part of an approved hazardous area system: Intrinsic safety
ground must be connected to terminal #2 and must be less than 1 ohm with
respect to earth ground. Refer to control drawing 225-1005.
• When used as part of an approved hazardous area system: Intrinsic safety
ground must utilize a grounding electrode independent of the protective
earth ground.