RM-8AI2 Usage Tips

This eight channel analog input module offers the convenience of pre-wired yet flexible direct field wiring. Two wires from each input device are wired to consecutive screw terminals on the –F (field style) wiring base. The even numbered terminals are individually configurable to connect to either ground (for internally powered instruments) or to DC power (for loop-powered transmitters).

Return Wire Power/Ground Jumper

With the module removed from the base, use a small screwdriver to lift open the hinged door in the module’s base. (The door is the flat plate containing the wiring legend.) Each input channel has a jumper that may be set for either DC power or ground. A legend in the circuit board indicates the correct position.

Field Replaceable Current Shunt

Each 4-20 mA input channel has a 100 ohm precision shunt across its input to develop a 2 volt signal when a full scale 20 mA is applied. This shunt is located in the module’s base, giving you the advantage of maintaining a continuous circuit even if the module is removed from the base. If excessive voltage is applied to an input, this shunt will blow like a fuse to protect the circuit. These shunts are installed in sockets to allow easy field replacement. A spare shunt is provided for your convenience. These shunts are precision devices that should only be replaced with authorized factory replacements.

Open Loop Detection

This module can detect and report an open instrumentation loop on its input. By allowing the module to report a negative value if the current falls below 4 mA, low limit logic in your DCS, PLC, RTU or computer can signal the loss of current. To enable this feature, select the "Go Negative Below 4 mA" setting for each individual channel.

Input Update Time

These 16 bit precision analog inputs integrate the signal using advanced signal correlation techniques. Superior noise rejection results from this integration, which takes approximately 50 mS per channel. Unused channels may be disabled in the Analog Channel Definition Window by selecting the feature "Disable Channel". Disabled channels are not scanned, speeding up the polling of the remaining channels. It should be noted that eight channel input modules scan all inputs at a rate slightly faster than the high density module.