Emerson ROC827 instruction manual Issued Mar-06 Communications

ROC827 Instruction Manual

second per poll for each device, so with five devices per channel the maximum poll time for the channel would be five seconds.

Note: The ROC827 does not support HART devices configured in Burst mode (in which the device sends information without a prior request). If you have a HART device configured in Burst mode, use a hand-held Field Communicator to turn off Burst mode before you connect the device to the ROC827.

The HART module provides “loop source” power (+T) and four channels (1+ through 4+) for communications. The +T power is current-limited.

When powered by the ROC827, terminal +T is connected in parallel to the positive (+) terminal on all of the HART devices, regardless of the channel to which they are connected. Channel 1+ is wired to the negative (–) terminal of a single HART device, or in parallel to the negative terminals of the devices. Likewise, channel 2+ is wired to the negative (–) terminal of a single HART device, or in parallel to the negative terminals of a second group of HART devices.

When powered by an external device, the positive (+) terminal from the power source is connected in parallel to the positive (+) terminal on all of the HART devices, regardless of the channel to which they are connected. Channel 1+ on the HART module is wired to the positive (+) terminal of the HART device. The power source negative (–) terminal is connected to the channel’s COM terminal and to the negative (–) terminal of a single HART device, or in parallel to the negative terminals of the HART devices.

Switches on the module board allow channel-by-channel selection as an Analog Input (IN) or Analog Output (OUT). The switches for Channel 2 and 4 are located on the front of the module, while the switches for channel 1 and 3 are located on the back of the module. Use a pin to move the switches to the desired state (refer to Figures 5-8 and 5-9).

Note: Always set the IN or OUT switches before wiring the switch or applying power.

Issued Mar-06 Communications 5-17