DI–710 Series and DI-715B Series Hardware Manual
Accessories
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DI-5B47 Linearized Thermocouple Input Modules
Each DI-5B47 thermocouple input module provides a single channel of thermocouple input which is filtered, iso-
lated, amplified, linearized and converted to a high level analog voltage output (see block diagram). This voltage out-
put 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.
The DI-5B47 can interface to eight industry standard thermocouple types: J, K, T, E, R, S, N, and B. Its correspond-
ing output signal operates over a 0 to +5V range. Each module is cold-junction compensated to correct for parasitic
thermocouples formed by the thermocouple wire and screw terminals on the mounting hardware. Upscale open ther-
mocouple detect is provided by an internal pull-up resistor. Downscale indication can be implemented by installing
an external 47M
Ω
resistor, ±20% tolerance, between screw terminals 1 and 3.
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 on the com-
puter side.
After the initial field-side filtering, 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%.
A special circuit in the input stage of the module provides protection against accidental connection of power-line
voltages up to 240VAC.
