Continuum I/O System Reference
25
Measuring Temperature
UI-8-10 inputs may be configured to sense temperature by configuring one of the
module’s inputs appropriately. This is done by setting the Electrical Type to either
ACC
Temp (DEG F)
or
ACC Temp (DEG C)
. Connect a resistive thermistor sensor to that
input terminal. The following is a schematic representation of the connection:
One lead connects to a numbered input terminal, the other to a return terminal.
To use the input for temperature sensing, the pull-up reference resistor must be
connected into the circuit, therefore,
the reference resistor switch for this input must
be placed in the ‘on’ position
. When the input point is configured as a temperature
input, the controller utilizes a look-up table to convert from a voltage reading to a
temperature reading in degrees Fahrenheit or Celsius.
Caution
Never apply a voltage to a thermistor—doing so alters the thermistor’s accuracy and
reliability. In fact, it’s a good idea to replace any thermistor that has had any sort of
voltage applied to it.
Maximum Wire Runs for Thermistors
To keep thermistor errors minimal, limit the length of wire runs to the maximum for the
gauge wire you select.
The following two pages include three tables that indicate the maximum length runs for
wires of various gauges to keep errors within certain temperature limits when using
thermistor elements.
IN x
RET
Thermistor
UI-8-10
Technical Manuals Online! - http://www.tech-man.com
To Next Page
Loading...