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General Purpose Input Modules, with DC Excitation
FEATURES
● INTERFACES TO DC DISPLACEMENT TRANSDUCERS AND OTHER
DEVICES REQUIRING A STABLE DC SUPPLY
● HIGH LEVEL VOLTAGE OUTPUTS
● 1500Vrms TRANSFORMER ISOLATION
● ANSI/IEEE C37.90.1-1989 TRANSIENT PROTECTION
● INPUT PROTECTED TO 240VAC CONTINUOUS
● FULLY ISOLATED EXCITATION SUPPLY
● 100dB CMR
● 1KHz SIGNAL BANDWIDTH
● ±0.10% ACCURACY
● ±0.02% LINEARITY
● ±20µV/°C DRIFT
● CSA CERTIFIED, FM APPROVED, CE COMPLIANT
● MIX AND MATCH OM5 TYPES ON BACKPANEL
DESCRIPTION
Each OM5-DT general purpose input module provides a single channel of
transducer input which is filtered, isolated, scaled, and converted to a high
level analog voltage output (Figure 1). This voltage output is logic switch
+EXC
+In
DC LVDT
or Other
Transducer
–In
–EXC
Backpanel
Term Block
FIGURE 1. OM5-DT Block Diagram.
OM5-DT
4
LPF
4
Surge
6
Suppression
3
and
5
Protection
2
3
1
1
NC
2
NC
+V
Isolated
–V
Field-Side
Power
26
controlled, which allows these modules to share a common analog bus
without the requirement of external multiplexers.
The modules are designed with a completely isolated computer side circuit
which can be floated to ±50V from Power Common, pin 16. This complete
isolation means that no connection is required between I/O Common and
Power Common for proper operation of the output switch. If desired, the
output switch can be turned on continuously by simply connecting pin 22,
the Read-Enable pin to I/O Common, pin 19.
The OM5-DT can interface to devices which require a precision 10VDC
excitation supply. The 1kHz bandwidth significantly reduces ripple and
noise inherent in these devices.
Transducer excitation is provided from the module by a very stable 10V
source. The excitation supply is fully isolated, allowing the amplifier inputs
to operate over the full range of the excitation voltage. This feature offers
significant flexibility in real world applications. Eight full scale input ranges
are provided, from ±1V to ±10V, producing ±5V full scale output.
The input signal is processed through a pre-amplifier on the field side of
the isolation barrier. This pre-amplifier has a gain-bandwidth product of
5MHz and is bandwidth limited to 1kHz. After amplification, the input signal
is chopped by a proprietary chopper circuit. Isolation is provided by
transformer coupling, again using a proprietary technique to suppress
transmission of common mode spikes or surges. The module is powered
from +5VDC, ±5%.
Special input circuits provide protection of the signal inputs and the
isolated excitation supply up to 240VAC.
Isochopper™
Amplifier
Pat Pending
+V
–V
Isolated
Excitation
Isolated
Source
Computer-Side
Power
20
LPF
V
OUT
19
I/O Common
22
RD EN\
17
+5V
Power
Oscillator
16
Power
Common
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