Dataq DI-720-EN, User Manual

Page: 95 / 108

DI–720/DI–722/DI–730 Series User Manual
Accessories
85
DI-5B36 Potentiometer Input Modules
Each DI-5B36 Potentiometer input module provides a single channel of Potentiometer input which is filtered, iso-
lated, amplified, and converted to a high level analog voltage output (see block diagram). This voltage output is logic
switch controlled, which allows these modules to share a common analog bus without the requirement of external
multiplexers.
The DI-5B 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.
Excitation for the potentiometer is provided from the module by two matched current sources. When using a three-
wire potentiometer, this method allows cancellation of the effects of lead resistances. The excitation currents are very
small (less than 1.0mA) which minimizes self-heating of the potentiometer.
Signal filtering is accomplished with a six-pole filter which provides 95dB of normal-mode-rejection at 60Hz and
90dB at 50Hz. Two poles of this filter are on the field side of the isolation barrier, and the other four are in the output
stage. After the initial field-side filtering, the input signal is chopped by a proprietary chopper circuit. Isolation is pro-
vided by transformer coupling, again using a proprietary technique to suppress transmission of common mode spikes
or surges. The module is powered from +5VDC, ±5%.
A special input circuit on the DI-5B36 module provides protection against accidental connection of power-line volt-
ages up to 240VAC.
Ordering Information
MODEL INPUT RANGE OUTPUT RANGE
DI-5B36-01 0 to 100
Ω
0V to +5V
DI-5B36-02 0 to 500
Ω
0V to +5V
DI-5B36-03 0 to 1k
Ω
0V to +5V
DI-5B36-04 0 to 10k
Ω
0V to +5V