Honeywell IAQPoint2 Guide De Démarrage Rapide page 76

IAQPoint2™
The LonWorks interface has seven network variables of type SNVT_switch� These
are each used simply as a bit� Thus the only output values that will ever be
produced are a LonMark "on" or "off", which are (100�0; 1) and (0�0; 0) respectively�
Similarly, the only input values that will be accepted are "on" and "off"� Other
values will be ignored�
Each of the three sensor functional blocks has a network variable output for faults
of type SNVT_switch� This will hold the value "off" if the IAQPoint2 is working
correctly or "on" if there is some fault� These are provided to facilitate a simpler
alternative to nvoStatus which external controllers can read�
Finally each of the three sensor function blocks has an NVI and an NVO for
setpoints� Writes of illegal or out-of range values to the NVI will be ignored� Valid
writes to the NVI will be reflected on both the local user interface and the NVO�
Whenever contradictory values are written via the local UI and the NVI, the value of
whichever interface writes last will be retained�
The behavior of these functional blocks is a listed below�
CO2 Sensor Functional Block
CO2 concentration is conveyed both as SNVT_ppm and as SNVT_lev_percent�
This percentage is computed using 2000 ppm as full scale� On models with a VOC
sensor, the concentration is reported both as an equivalent ppm reading and as an
air quality index� The variable nvoIAQGood provides the simplest output -- this
takes the value "on" if the gas level is less than the setpoint and there is no fault;
otherwise, it takes the value "off"� Note that when the VOC sensor is fitted the
value of nvoCO2SetPtPpm may have a rounding error of up to 16 ppm�
Temperature and Humidity Sensor Functional Blocks
These functional blocks report the temperature and humidity and are present on
all LonWorks interfaces� However, in models without the necessary sensor the
nvoFault variables will always be "on" and the LonMark block will always "fail self
test"�
Occupancy Sensor Functional Block
The IAQPoint2 does not contain hardware so sense actual occupancy� Instead,
this block reports the status of the occupancy timer via SNVT_occupancy and as
SNVT_switch� The timer is started by pressing the [Occ] button as shown in Figure
27 and Figure 28� Additionally, the NVI can be used to force the "occupied" icon to
appear at the top of the main screen as shown in Figure 21� The two instances of
SNVT_occupancy use the values OC_OCCUPIED and OC_UNOCCUPIED� All other
values will be ignored�
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