Low-Level Pulse Input Module; Rtd Input Module; Hart Interface Module - Emerson Fisher FLOBOSS 407 Instruction Manual

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FloBoss 407 Instruction Manual

3.2.9 Low-Level Pulse Input Module

The Low-Level Pulse Input module counts pulses from pulse-generating devices having a voltage range

of 30 millivolts to 3 volts peak-to-peak. The module can accommodate one pulse input.

Input pulses are counted by a 16-bit counter that is capable of storing up to 22 seconds of pulse counts

for a 3 KHz input signal. The module provides electrical isolation between the input pulses and the

ROC/FloBoss power supplies.

The Resistance Temperature Detector (RTD) module monitors the temperature signal from an RTD

source. The module can accommodate one input from a two-, three-, or four-wire RTD source.

The active element of an RTD probe is a precision, temperature-dependent resistor, made from a

platinum alloy. It has a predictable positive temperature coefficient, meaning its resistance increases

with temperature. The RTD input module works by supplying a small current to the RTD probe and

measuring the voltage drop across it. Based on the voltage curve of the RTD, the signal is converted to

temperature by the ROC/FloBoss firmware.

The HART Interface Module provides communications between a ROC/FloBoss and other devices

using the Highway Addressable Remote Transducer (HART) protocol. The module has its own

microprocessor and mounts in the I/O module sockets of a ROC/FloBoss.

The HART Interface Module communicates digitally to HART devices through the I/O termination

blocks associated with the module position. Each HART module contains two separate channels. Each

channel polls all HART devices connected to it before the other channel is polled. Each channel can be

configured to operate in either the point-to-point mode or the multi-drop mode. In the point-to-point

mode, each module channel supports one HART device.

In the multi-drop mode, each channel can support up to five HART devices for a total of ten devices for

each module. By using the multi-drop mode with multiple HART modules, up to 32 HART devices

(limited by the software) can be supported by a single ROC/FloBoss.

3-6

Rev 5/00

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