6
Overview
CTs can measure lower currents than they were designed for by passing the wire through the CT more than
once. For example, to measure currents up to 1 amp with a 5 amp CT, pass the wire through the CT once,
then loop back around the outside of the CT, and pass the wire through the CT again. Repeat until the wire
passes through the CT 5 times. The CT is now effectively a 1 amp CT instead of a 5 amp CT; therefore, set
the CT current rating to 1 amp as described in section
4.2.3 Energy Configuration
. In general, the
current rating of the CT is divided by
n
where
n
is the number of times that the wire passes through the CT.
1.3 LonTalk
®
Network
The WattNode communicates using Echelon's
®
LonTalk network protocol. This interoperable network
standard supports many physical media and allows easy communication between LonTalk compatible
devices and monitoring computers. Network variables interface the WattNode to the network. Each device
on the network may have both input and output network variables. During network setup, output network
variables may be bound (connected) to input network variables of the same type. Whenever an output
network variable is updated, the new value is propagated over the network, and all devices which have
input network variables bound to the updated output will update their internal copies of the variable.
1.3.1 LonMark
®
The WattNode is certified as meeting LonMark Interoperability Guidelines version 3.0. The guidelines
ensure that products from different manufacturers can be integrated together in a network. The guidelines
also specify consistent documentation and network variable organization to speed installation.
1.3.2 External Interface File (XIF)
The external interface file contains definitions for all the network variables in the WattNode and hardware
parameters pertaining to the node, such as transceiver type. The XIF file also contains self-documentation
information about the WattNode and all of the network variables. Most network management tools can use
XIF files to pre-install a node before the actual node has been connected to the network. Some network
management tools require the use of the XIF file during installation. Every order of WattNodes includes a
disk with the required XIF file. If you use the XIF file for installation, it is important that the XIF file
matches the WattNode version and transceiver type.
