EUROPE (EMEA)
Tel: +44 (0)1582 723633
Fax: +44 (0)1582 422283
AMERICAS
Tel: +1 281 571 8065
Fax: +1 281 571 8069
ASIA PACIFIC
Tel: +65 6 487 7887
Fax: +65 6 487 7997
E-mail: [email protected] Web site: www.mtl-inst.com
5.08 ins (129 mm)
1.22 ins
(31 mm)
Mode
FBT-3
Fieldbus Monitor
2.75 ins
(69.9 mm)
Operation
The FBT-3 can be connected to the network using the clip leads. The
test leads are polarity sensitive and the Monitor will not operate if
they are reversed. When first connected to a fieldbus, a Version
number is displayed for 1 second. The MODE button is used to select
from several network parameters that can be examined with the
Monitor. When a function is selected, the LCD display reads “- - -”
until the monitor has collected and processed the data. After that,
the measured value is shown. The indication “OK” is shown if the
measured value is within the acceptable range (as defined by the
fieldbus specification). The rotating symbol in the lower right corner
of the display indicates that there is network activity. A horizontal
bar under the rotating symbol indicates that a frame was detected,
but could not be decoded. This is not a maintained function. I.e., if a
single “bad” frame is detected, the horizontal underbar will only be
on the display for a short time. Periodic “bad” frames will cause the
underbar to blink. Following are more detailed explanations of each
of the monitor’s modes:
Power
The DC voltage on the network is shown. Measurements over 9V are
OK. The maximum displayed value is 25.5V.
LAS
If there is any activity on the network, the Link Active Scheduler (LAS)
should be sending out Probe Node frames. The Monitor measures the
signal level of the Probe Node frame. The signal level is in millivolts.
Device
If there are fieldbus devices active on the network, the Monitor counts
them. If the count has remained the same since the Device function was
selected, the display shows “OK”. Note that the LAS is considered a
device and as such is included in the count. Devices are counted by
watching their response to a Pass Token. If a device does not respond
to the Pass Token, it is taken off an internal list and the count will be
reduced. The device may still show up on PC monitoring software
because the LAS will not take it off of the Live List until it has failed to
respond to a Pass Token three times in a row. If a device leaves the
network, “-” is displayed. If a new device is added, the display shows “+”
Low
The signal level of the device with the weakest signal is shown.
The device’s address (hexadecimal) is displayed behind the word
"LOW". This will be the lowest signal level reading from a device
since the tester was connected to the fieldbus. Measurements greater
than 150mV are OK
Noise Av
The noise on the network is measured during the silence between
frames. The value is averaged over 10 measurements. Measurements
of less than 75mV are OK.
Noise Pk
The peak noise recorded since this function was started is displayed.
Measurements of less than 75 mV are OK.
New
If a new device is to be added to the network, it must respond to the
Probe Node frame sent by the LAS. The Monitor measures the signal
level of the new device’s response. Measurements greater than 150mV
are OK. The address (in hexadecimal) of the new device is displayed also.
Specifications
The Monitor is powered by the fieldbus and draws approximately
10mA of current from the network (depending on bus voltage and
ambient temperature).
Operating temperature range
0 — 50ºC
Dimensions
12.9 × 7.0 × 3.1cm
Weight
150g
May 2004
