Continuum I/O System Reference
23
Each input includes a low-pass filter after the pull-up formed by a series resistor and a
parallel capacitor. The resistor is utilized for over-voltage protection in limiting current to
two protection diodes (not shown). Note also that all input returns are combined and must
be directly connected to earth ground. It is possible to have more than one input share a
single return wire. Keep in mind that the current through each input is approximately
0.3mA, so voltage drops occur with long runs of small gauge wire.
Pull-up Reference Resistor Selection Switches
In some measuring instances it is desirable that there be no pull-up resistor. Instead of
physically removing or cutting the resistor off the printed circuit board, the input module
includes a pull-up resistor selection switch (labeled Swdis in the diagram) for each input
position. This switch allows you to select whether or not you want a pull-up resistor in the
circuit. A small 8-position switch module is accessible from the front of the module when
the door is opened.
These switch modules are commonly called “DIP Switches” and require a small object
such as the tip of a pen or a small screwdriver to operate them. Each switch position acts
as a “slide switch”. Pressing the raised slide marker to the side marked “on” closes or
enables the switch. To open or disable the switch position, press the slide marker over to
the “off” side.
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Slide marker
moves left and right
UI-8-10
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