ROC364 Instruction Manual
3-2
Input and Output Modules
Rev Jun/05
SENSITIVE
STATIC
DOC0034C
Figure 3-1. Typical I/O Module
3.2.1 Analog Input Loop and Differential Modules
The Analog Input Loop (AI Loop) and Analog Input Differential (AI Differential) modules are used for
monitoring current loop and voltage output devices. Each AI module uses a scaling resistor for scaling
loop current to achieve the proper input voltage.
The AI Loop module provides a source voltage for powering current loop devices and can be used as a
single-ended voltage output. The AI Differential module monitors loop current or voltage input from
externally-powered devices and provides electrical isolation from the ROC power supplies.
3.2.2 Analog Input Source Module
The Analog Input Source (AI Source) module monitors current loop or voltage output devices. The
Analog Input Source module provides a regulated 10-volts source for powering a device, usually a low
power transmitter, and uses a scaling resistor for converting loop current to input voltage.
3.2.3 Analog Output Source Module
The Analog Output Source (AO Source) module provides both a current and a voltage output for
powering analog devices. These outputs are isolated from each other and can be used simultaneously. A
scaling resistor provides a way to set the minimum loop resistance of the current loop to 0 ohms
(installed) or 220 ohms (removed).
