54
Communication & Verification
DENT Instruments
PowerScout HD
The PSHD meter communicates using IEEE 802.3 Ethernet connectivity running at a 10/100 Mbps.
Verification of the meter settings over Ethernet includes ensuring that the IP address of the meter is
within a range that allows communication with a host (if static) or is set for DHCP, allowing the meter to
be assigned an address by a DHCP server as described below.
DHCP
If the PSHD meter is configured for DHCP when the meter is powered on, or the Ethernet cable is
inserted, the meter is assigned an IP address by the DHCP server. This address appears on the meter’s
LCD user interface or can be found through connection with ViewPoint HD or the PSHD Web App. The IP
address assigned to the meter should be regarded as a
temporary address
as the address may change
between power cycles making it difficult for the host system to know how to find the meter on the
network. One common approach is to set the PSHD for DHCP so that the address can be assigned by a
DHCP server and then change that IP address to static once the connection is made. PSHD meters are
set to use DHCP as a default setting to facilitate this approach.
STATIC
IP
If the PSHD meter is set to a static IP, its address should be assigned by an IT department to avoid
multiple devices on the same network. This scheme is usually used when an RTU is expecting to find the
meter at a specific IP address.
Protocol Verification
The network protocol is typically specified as part of the installation. BACnet MS/TP and Modbus RTU
are the two communication protocols that operate over an RS-485 serial network and BACnet IP and
Modbus TCP are the protocols over Ethernet. Each combination of interface and protocol require
specific registers settings described below. The scope of this section is to use either the LCD user
interface or software tools to quickly confirm or change settings to match an existing specification.
Further information and optimization tips are covered in the section on RTU programming.
Modbus Settings
M
ODBUS
RTU
S
ETTINGS
Device Address
: In a Modbus network, each device must be assigned a
unique slave address.
Valid
Modbus addresses are 1-240 (keep in mind the PS48HD requires 15 addresses beyond Element A, the
PS24 requires 7 addresses beyond Element A, and the PS12HD requires 3 addresses beyond Element A)
.
The slave address of the power meter sets the register address for
ELEMENT A
. Adjacent elements B, C,
D, etc. are accessed by incrementing the slave address by 1. The slave address of the PSHD meter needs
to be set to match the address expected by the RTU and is normally part of the network specification.
The default address for Element A is 1.
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