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monitoring of
fieldbus networks
FBT-4
The Fieldbus Power & Signal Probe, FBT-4,
is used to examine the operation of a live
F
OUNDATION
fieldbus™ network without interfering
with its operation. The Probe is intended for
maintenance personnel to verify network operation
or to troubleshoot an errant network. The Power
and Signal Probe is designed to help instrument
technicians quickly determine if bus power and
signal levels are within specification at individual
points on a fieldbus network segment. For example,
if a fieldbus transmitter suddenly goes off-line, the
FBT-4 can be used to determine if the problem resides
in the transmitter itself or is due to an open or short in
the network cable system. Inexpensive and portable,
the FBT-4 runs on bus power and thus requires no
batteries or other external source of power.
Operation
One red and two green LEDs indicate the status
of the fieldbus network. They are labeled Signal,
Voltage, and Reversed. A lit green LED indicates
that the network is performing satisfactorily. A lit
red LED signals an error condition. Following are
descriptions of the three indicators:
Signal indicates that there is bus activity. It will only
light if data traffic is detected with peak to peak
amplitude greater than 150 mV. The validity of the
data is not checked. You will notice that the LED
blinks when there is bus activity. It is driven directly
by the frame data and is thus not powered during the
brief silence between packets.
Voltage indicates that the DC Voltage on the fieldbus
is greater than the 9.0V dc minimum that is required
by the fieldbus standard.
Reversed indicates that the FBT-4 probes have been
connected to the network incorrectly or that the
fieldbus has been wired with reversed polarity.
Connection
The pointed probe attached directly to the case of the
FBT-4 is the negative input and should be connected
to a negative point on the fieldbus. The red wire with
the pointed probe should be connected at a positive
point on the fieldbus. For hands-free operation, a
red mini-hook assembly is available which can be
attached to the end of the red pointed probe. A
black cable with mini-hook is also available to plug
onto the negative terminal of the FBT-4.
Specifications
The Monitor is powered by the fieldbus and draws
12-15mA of current, depending on bus voltage and
ambient temperature.
Operating temperature range: 0 - 50ºC
Weight: 300g
Size: 11.8 × 5.0 × 2.1cm
Monitors:
DC power
Polarity
Packet
traffic
◆
Checks for basic fieldbus
operation
Bus powered
◆
◆
May 2004
Relcom
