CR300-Series Datalogger
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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.
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