Network
Configuration
17
3.3 Network Variables
The WattNode uses LonMark interoperable SNVTs (Standard Network Variable Type) and object
definitions. The WattNode is designed as three independent sensor objects and one supervisory node
object. The three objects report energy, power and demand. They may be independently activated,
configured, and bound on the network. See section
4 Operation
for detailed information on using and
configuring the measurement objects.
The WattNode is programmed with self-documentation information formatted according to “LonMark
Interoperability Guidelines version 3.0”. There is a self-documentation string for the whole WattNode that
contains the LonMark header and the text names of each sensor object supported by the WattNode. These
are followed by a brief description of the WattNode. The WattNode uses the following standard program
IDs:
Transceiver
Standard Program ID
TP/XF-78 80:00:22:15:00:0A:01:00
TP/FT-10 80:00:22:15:00:0A:04:00
Table 3.2: LonMark Standard Program IDs
The WattNode also comes with an external interface file (XIF), which defines all of the network variables,
the standard program ID, and transceiver parameters. The XIF file may be requested by network
management software during installation, and is particularly useful if you wish to configure the network for
a WattNode before physically installing the WattNode.
The WattNode contains four LonMark objects: Node Object (#0), Energy Measurement Object (#1), Power
Measurement Object (#2), and Demand Measurement Object (#3). Each object has several associated
network variables (NVs). Each NV has a self-documentation string with a LonMark header indicating
object number, variable type—LonMark object, manufacturer specific, or configuration—and variable
number. The LonMark header is followed by text describing the NV.
The network variable names are prefixed with three letters indicating the variable type:
nvi – Input to the WattNode.
nvo – Output from the WattNode.
nci – Configuration network variable; normally an input to the WattNode, but can be read to determine
the current configuration. All configuration variables are preserved during power outages.
3.3.1 Authentication
For installations where the WattNode will be used for billing, several of the network variables should be
protected from unauthorized tampering. The LonTalk protocol supports a feature called authentication,
which prevents unauthorized nodes from accessing specified network variables. The network management
software must be used to enable authentication for each network variable being protected. Once protected,
the network variable may only be accessed by nodes that know the authentication key. If authentication is
enabled, be sure to record the authentication key. The following network variables should be protected
with authentication if the WattNode is being used for billing or other critical applications:
nviRequest
,
nviTimeSet
,
nciGain
,
nciCTAmps
,
nciDemPeriod,
and
nciDemSubints
(the last two only pertain to demand
measurements, and need not be authenticated if demand is not being used).
