Campbell CR300 series, Operator'S Manual

Page: 47 / 86

CR300-Series Datalogger
37
Advantages of PakBus are as follows:
•
Simultaneous communication between the CR300 and other devices.
• Peer-to-peer communication — no PC required. Special CRBasic
instructions simplify transferring data between dataloggers for
distributed decision making or control.
•
Data consolidation — other PakBus dataloggers can be used as
"sensors" to consolidate all data into one CR300.
•
Routing — the CR300 can act as a router, passing on messages
intended for another Campbell Scientific datalogger. PakBus supports
automatic route detection and selection.
• Short distance networks — with no extra hardware, a CR300 can talk
to another CR300 over distances up to 30 feet by connecting transmit,
receive and ground wires between the dataloggers.
In a PakBus network, each datalogger is set to a unique address. The default
PakBus address in most devices is 1 . To communicate with the CR300, the
datalogger support software must know the CR300 PakBus address. The
PakBus address is changed using
Device Configuration Utility
, CR300 Status
table, or PakBus Graph software.
CRBasic PakBus instructions include:
•
GetDataRecord()
• GetVariables()
•
SendData()
•
SendGetVariables()
• SendVariables()
6.5.7 Internet Communications
The internet protocols listed in Section 7.10 ,
Communication – Specifications
(p. 48)
, are supported by the CR300 when using a cell modem with the PPP/IP
key enabled. The most up-to-date information on implementing these protocols
is contained in CRBasic Editor Help .
6.6 Grounding – Details
Proper grounding lends stability and protection to a data acquisition system. It
is the easiest and least expensive insurance against data loss – and often the
most neglected. The following terminals are provided for connection of sensor
and CR300 grounds:
•
Signal Ground ( ⏚ ) — reference for single-ended analog inputs,
excitation returns, and as a ground for sensor shield wires.
• Power Ground ( G ) — return for 5V, 12V, and digital sensors. Use of
G grounds for these outputs minimizes potentially large current flow
through the analog-voltage-measurement section of the wiring panel,
which can cause single-ended voltage measurement errors.
•
Earth Ground Lug ( ⏚ ) — connection point for heavy-gauge earth-
ground wire. A good earth connection is necessary to secure the
ground potential of the CR300 and shunt transients away from
electronics. 14 AWG wire, minimum, is recommended.