BENTLY NEVADA 9200 and 74712 Velocity Transducers

Velocity Transducer

Bently Nevada Seismoprobe Velocity Transducer Systems are
designed to measure absolute (relative to free space)
bearing housing, casing, or structural vibration. The two-wire
systems consist of a transducer and appropriate cable.
The Seismoprobe family of velocity transducers is a two-wire
design that uses moving-coil technology. It provides a
voltage output directly proportional to the transducer's
vibration velocity.
Moving-coil transducers are less sensitive to impact or
impulsive excitation than solid-state velocity transducers,
which are inherently accelerometers with embedded
integration electronics.
Moving-coil transducers are less sensitive to impact or
impulsive excitation and can represent a good choice for
certain applications. Because they don’t require external
power, they are convenient for portable measurement
applications.
For most installations, Bently Nevada's Velomitor
family of velocity transducers, which incorporate
solid-state technology, provide improved
performance and ruggedness for casing velocity
measurement applications.

Available Types
Two types of Seismoprobe Velocity Transducer
are available:
l 9200: The 9200 is a two-wire transducer
suitable for continuous monitoring or for
periodic measurements in conjunction
with test or diagnostic instruments. When
ordered with the integral cable option,
the 9200 has excellent resistance to
corrosive environments without need of
additional protection.
l 74712: The 74712 is a high temperature
version of the 9200.
Interconnect cables are available for
connecting the 9200 and 74712 transducers to
other instruments. These cables are available
in various lengths with or without stainless steel
armor.
When ordering the 9200 and 74712
Seismoprobe Velocity Transducers, expect
approximately a six week lead time. That lead
time can vary based on component availability
and configuration. For projected lead times for
your specific order, contact your local Bently
Nevada representative.
Most common machine malfunctions
(unbalance, misalignment, etc.)
occur on the rotor and originate as an
increase (or at least a change) in
rotor vibration. For any individual
casing measurement to be effective
for overall machine protection, the
system must continually transmit a
significant amount of rotor vibration
to the machine casing, or mounting
location of the transducer.
In addition, be careful to install the
accelerometer transducer on the
bearing housing or machine casing.
Improper installation may decrease
the transducer amplitude and
frequency response and/or generate
false signals that do not represent
actual vibration. Refer to the
appropriate instruction manuals and

Specifications
Specifications are at approximately +22°C
(+72°F) with 25 mm/s (1 in/s) of machine
casing vibration at 100 Hz (6000 cpm) with a 10
kΩ load unless otherwise specified.
Electrical
Sensitivity
20 mV/mm/s (500 mV/in/s),
±5% when properly
terminated and oriented at
the angle of calibration.
Calibration
Load
10 kΩ Terminal "A" to "B"
Output taken across pins "A"
and "B"
Sensitivity
Temperature
Coefficient
0.2%/°C
Frequency
Response-See
Theoretical
Velocity
Seismoprobe
Frequency
Response on
page 11.
4.5 to 1000 Hz (270 to 60,000
CPM); +0, -3dB typical.
10 to 1000 Hz (600 to 60,000
CAM); +0, -3dB typical.
15 to 1000 Hz (900 to 60,000
CPM); +0, -3dB typical.
Frequency
response
From minimum operating
frequency (see Ordering
Information) to 1 kHz (60,000
cpm); +0, -3dB typical.
Please contact Bently
Nevada for detailed
calibration data.
Dynamic
operating
range
2.54 mm (0.100 in) peak to
peak maximum
displacement.
Velocity
Range
25 mm/s (1 in/s) (at +22 °C of
casing vibration at 100 Hz
with a 10 kΩ load.
Coil
Resistance 1.25 kΩ ±5%
Locked Coil
Inductance 125 mH, typical

Amplitude
Linearity
±5% from 0.01 to 5.0 in/s
(0.254 to 127 mm/s) at 100Hz
(6000CPM)
Shock
resistance
Withstands 50 g peak
maximum acceleration
along non-sensitive axis.
Transverse
sensitivity
±10% maximum of the
sensitive axis sensitivity at 100
Hz and 1.0 in/s (2.54 cm/s)
Polarity of
output signal
Pin A goes positive with
respect to Pin B when the
transducer case velocity is
towards the connector.
Lead wire
length
305 meters (1,000 feet)
maximum between
Seismoprobe Velocity
Transducer and 3300 or 3500
Monitor. Consult manual for
frequency roll-off at longer
lengths.
Environmental Limits
Operating and
Storage
Temperature:
9200: -29°C to +121°C
(-20°F to +250°F).
74712: -29°C to +204°C
(-20°F to +400°F).
Environment
Dust and moisture resistant.
Contact your Sales
Professional
regarding
transducer
operation in a
radiation
environment.
Relative
Humidity
To 95%, noncondensing.
100%, non-submerged, when
ordered with integral cable.
Maximum Use
Altitude
2000 m (6,561 ft) above sea
level.