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M8687 • REV E
July 2017 Page
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continued to within 1 to 2 inches (25 to 50mm) of the transmitter terminals. The shield itself
should be connected to the provided shield terminal. The shield connection should be as
short as possible. Ensure that all shields are connected only at one end, preferably at the
transmitter. Alternate shield connections are possible such as to instrumentation grounds,
etc. In general, connection of shields to earth grounds should be avoided except at one cen
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tral earth grounding point for a complete system as “ground loops” may be created, which
can introduce unwanted power frequency pickup.
SENSOR MALFUNCTION
The signal conditioners are provided with a sensor malfunction detector, which causes the
output current to drop below 3.5 mA, the SENSOR OK LED to extinguish and the Display
(5544 & 5545 only) to read zero, in the event of an open circuit. The 5535 and 5545 also
detect incorrect polarity or shorted cable conditions.
CALIBRATION
NULL OFFSET
The offset calibration can be checked as follows:
Disconnect the transducer cable leads from the signal conditioner and connect the following
in its place:
•
Model 5534, 5544: Short circuit transducer connections, except for -40X, -50X,
-60X and -70X (piezovelocity) units which require a resistor as specified for Models
5535 & 5545.
•
Model 5535, 5545: Tie the transducer connections together as follows:
4mA sensor current source conditioners — 2.49K ohm resistor
10mA sensor current source conditioners — 1K ohm resistor
No sensor current source conditioners — short circuit
To adjust, remove the plastic plug from the Z (Zero) control and adjust the latter to obtain
exactly 4 mA output. Remove the short (or the resistor) and reconnect the transducer cable.
SPAN
The 20 mA output (SPAN) is factory set to the full scale value indicated on the nameplate
and is not field adjustable. The most reliable way to check the calibration of the sensor and
signal conditioner as a system is to compare the indicated vibration with an independent,
accurate vibration measurement at the same location.
FORMULA:
Measured mA - 4 mA
20 mA - 4 mA
EXAMPLE:
Measured mA
Full Scale Vib
Actual Vib
<3.5
1.0 ips, pk
Sensor fault
4.0
1.0 ips, pk
0.0 ips, pk
12.0
1.0 ips, pk
0.5 ips, pk
20.0
1.0 ips, pk
1.0 ips, pk
STARTUP CURRENT
The signal conditioners employ a DC-DC converter. As with all converters of this nature, a
large current spike occurs at startup. The current spike has a peak of 100 mA and lasts for
40 ms. Care should be exercised when wiring several units onto one supply. Power supplies
without adequate capacity will not allow the units to start properly. The internal power sup
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ply fuse may open as a result of this condition.