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E-mail: [email protected] Web site: www.mtl-inst.com
Push the Monitor's Mode button once to get the LAS function.
The LAS signal level reading should say "OK" and show the
signal level in millivolts:
LAS Signal (mV) Wire Condition
350 or more
Excellent
200-350
Good
150-200 Marginal
150 or less
Not Good
Push the Monitor's Mode button three times to get the NOISE
Average reading. It should say "OK" and display the average
noise level:
Noise Level (mV)
Wire Condition
25 or less
Excellent
25-50
Good
50-75
Marginal
75 or more
Not Good
Wire System Testing
A complete fieldbus wire system, with two terminators and other
wiring blocks installed, can be tested before field devices are
connected. This is done in the same way as the wire testing described
previously except that the Test Terminator is not used.
Note: The wiring system cannot have fieldbus devices attached to
it during testing. The Wiring Validator is not capable of providing
power to the fieldbus devices and its signal generator will interfere
with any data transmission that the fieldbus devices attempt to
initiate.
If the wiring system has two terminators installed (as required
for proper fieldbus operation), test results will be comparable to
the results of the wire by itself. However, if too few or too many
terminators have been installed, the measured signal levels will be
inaccurate. The chart below shows the relative values of LAS signal
level that will be observed:
Terminators
LAS Signal (mV)
0 999
1 961
2 (correct
number)
760
3 637
Error Conditions
A blinking Low Battery light indicates that the outputs of the Wiring
Validator are shorted. The Low Battery light may also flash briefly as
the Wiring Validator is first attached to a wire pair. A continuously lit
Low Battery light indicates that the batteries need to be replaced.
Self Test
To verify that the Wiring Validator and the Fieldbus Monitor are
working correctly, connect them to each other through the Test
Terminator. Observe the power, signal, and noise values and verify
that they are within the following ranges:
Measurement Acceptable
Range
Power 9
to
10V
LAS Signal
700 to 800mV
Noise Average
less than 25mV
If the observed values fall outside of these ranges, replace the
batteries as described below. If the problem persists, contact Relcom
for assistance. The unit contains no user serviceable parts.
•
•
Additional Wiring Tests
To get a complete characterization of the fieldbus wiring, measure
the resistance between the individual conductors in the cable using
a standard ohmmeter.
Suggested measurements include:
The resistance between the twisted-pair wires
The resistance between each of the twisted pair wires and the
shield/drain (if present)
The resistance between the shield/drain and instrument ground
bar.
Readings of 100K ohms or higher are acceptable.
Additional System Requirements
A Relcom Fieldbus Monitor, FBT-6, is required to obtain signal and
noise measurements as described in these instructions.
Batteries
The FBT-5 requires four (4) AA Alkaline batteries
which are
not
included
. These must be installed prior to using the FBT-5. Access to
the battery compartment is obtained by unscrewing the four screws
on the back of the unit and removing the battery cover.
As a guide, the batteries will last about 12 hours with continuous use.
Specifications
The FBT-5 includes soft case, Test Terminator, clip leads, and
operating instructions.
Operating temperature range
0 to 50°C
Dimensions
12.9 × 7.0 × 3.1cm (5.1 × 2.8 × 1.2”)
Weight
600g
ORDERING INFORMATION
Description
Part Number
Fieldbus Wiring Validator
FBT-5
Fieldbus Monitor
FBT-6
•
•
•
Battery
Low
On
Power
Power
FBT-5
Fieldbus
Wiring Validator
5.08"
129 mm
2.75"
69.9 mm
1.22"
31 mm
Aug 2008
