AcquiSuite Ally 12 & 48 User Guide (Rev D)
36 | P a g e
COMMUNICATION & VERIFICATION - DETAILS
This section is intended to support the commissioning of the AcquiSuite™ Ally meter
by an instrumentation technician. In many cases, the electrical installation is
conducted ahead of the availability of the RTU or was performed by a different
installer. Often the technician is working in concert with a remote programmer who
is confirming the connectivity with a remote host system. A Digital Multimeter (DMM)
can be used to confirm measurements at the board terminals, if necessary.
• It is assumed that the meter is now powered up from the line voltage. It is safe
to touch the meter (including the user buttons) with the top cover removed
ONLY IF THE INTERNAL HIGH VOTLAGE COVER IS INSTALLED.
• Communications settings and real-time data values can be confirmed quickly
using the LCD interface. If significant setup modifications are anticipated, a
computer interface is recommended.
Physical Connections on an RS-485 Multidrop Network
The AcquiSuite™ Ally meter uses a 2-Wire Half Duplex RS-485 Implementation.
▪ Termination Resistors—are NOT included on the AcquiSuite™ Ally meter. If the AcquiSuite™ Ally
meter is at the end of a daisy-chain, then connect a 120-ohm leaded resistor between the + and
– terminal at the connector.
▪ Bias Resistors—are NOT included on the AcquiSuite™ Ally meter. Bias resistors are needed If the
idle conditions of the bus are in an indeterminant logic voltage. Bias resistors are usually located
at the master node and are usually 680 ohms for a RS-485 network.
▪ Network Topology—RS-485 is designed to be implemented as a daisy chain (series connections)
rather than star or cascade topologies.
▪ Signal Names—Some RS-485 devices use the terminology A/B while others use +/-. Note that A
is (-) and B is (+). Many manufacturers incorrectly label the terminals.
▪ Bus Loading—The AcquiSuite™ Ally meter is a 1/8
th
unit load allowing up to 256 like devices in
parallel.
To Next Page
Loading...