3.15.3 Operation principle
The operation of Slot#-mA#/RTD# can be described with a module diagram that
illustrates a single input-output combination of the actual function block. All the
modules in the diagram are explained in the next sections.
HIGH_WARN
HIGH_ALARM
Slot#–Input#
mA/RTD
module
AI_VAL
Limit
supervision
AI_DB#
AI_RANGE#
LOW_WARN
LOW_ALARM
Figure 67: Functional module diagram for input mode
AO_VAL
mA
module
Slot#–Output#
Figure 68: Functional module diagram for output mode
mA modules
mA current channels are used for input current measurement or output current
control in the range of -20…20 mA (DC current). The channels are configured for
particular input or output signal types by using channel-specific settings. When
Input 1 is activated with setting "-20…20mA", the Output 1 mode is blocked. If
Output 2 mode is activated with setting "-20…20mA", the Input 2 mode is blocked.
When a channel is configured as an output, the alarm outputs are deactivated.
RTD modules
RTD channels are used for resistance measurements and they are only input
channels. The inputs are configured for a particular input signal type by using the
channel-specific
Input mode
setting. The default mode for each channel is "Not in
use" which means that the channel is not sampled and the output value quality is
set accordingly.
All the channels are independent mA/RTD channels with separated protection,
filtering, reference, A/D-conversion and isolation. Thus, the RTD group is isolated
from mA channels.
The RTD inputs measure resistance in the range of 0...4000 Ω. All inputs are
calibrated and the calibration factors are stored on the module in nonvolatile
memory. The calibration circuitry monitors the RTD channels continuously and
reports the circuitry break of any channel.
Basic functions
1MRS759142 F
170 REX640
Technical Manual
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