Honeywell 4000 Series Relative Humidity Sensor; Timers - CAI Networks WebControl PLC User Manual

4.4 Honeywell 4000 Series Relative Humidity Sensor

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The WebControl hardware is designed to support one Honeywell 4000 series
relative humidity sensor. The Honeywell sensor output is 'almost' linear voltage
between 0 - +5V dc proportional to the relative humidity. This output is fed into one of
the A/D converter channels on the microcontroller. CGI command codes are
available to setup an upper and lower threshold for the humidity sensor that can then
be used in the Boolean expressions.
WebControl PLC has calibrated the humidity curve at 11%, 25%, 45%, and 78%.
However, due to sensor differences, some sensors may read the humidity value
different from actual value. Adding a 5K linear potentiometer (pot) in series with pin 3
(5V supply line) can help user to adjust your sensor match the accurate humidity
reading. If the humidity reading varies a lot, which is an indication your power supply
is not providing enough voltage to the board.

4.5 Timers

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WebControl PLC is different from BRE engine. User must write PLC code to
implement timers and delay functions. There is no hard limit of number of timers and
delays, There are blocking DELAY and non-blocking delay functions detailed in
section 6.2. WebControl PLC has built-in timer reference value for PLC coding:
CD Current date mm/dd/yyyy format
CT Current time hh:mm:ss format
CDW Current day of week
CH Current hour of day
CM Current minute of hour
CS Current second of minute
CDAY Current day of month
CMONTH Current month of year
CYEAR Current year
CTS Current Total Seconds from 1/1/2000
WebControl timer variables are in one mili-second minimum resolution. However,
due to high priority I/O like handling, like 1-wire interrupt, the accuracy of the timer
may in the range greater than 10mS. For how to program the timer functions, please
read Chapter 6 completely. There are a few examples described how to program the
WebControl PLC to act based on the input conditions and timer conditions.
Copyright(c) 2008,-2013 CAI Networks, Inc.
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WebControl PLC User Guide Version 3.02.17f
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