or rotor direction, compares these
measurements against user-programmable alarm setpoints, and generates
alarms when these setpoints are violated. The 3500/50 Tachometer Module is
programmed using the 3500 Rack Configuration Software and can be
configured with four different options:
1. Speed Monitoring, Setpoint Alarming, and Speed Band Alarming.
2. Speed Monitoring, Setpoint Alarming, and Zero Speed Notification.
3. Speed Monitoring, Setpoint Alarming, and Rotor Acceleration Alarming.
4. Speed Monitoring, Setpoint Alarming, and Reverse Rotation Notification.
The 3500/50 can be configured to supply conditioned Keyphasor® signals to the
backplane of the 3500 rack for use by other monitors, thus eliminating the need
for a separate Keyphasor module in the rack. The 3500/50 also has a peak hold
feature that stores the highest speed, highest reverse speed, or number of
reverse rotations (depending on channel type selected) that the machine has
reached. These peak values can be reset by the user.

Application Note
Bently Nevada Tachometer Modules are not designed for use independently as, or as a component
of, a speed control or overspeed protection system.
Bently Nevada Tachometer Modules do not provide protective redundancy nor the response speed
needed for reliable operation as a speed control or overspeed protection system.
Where provided, the analog proportional output is suitable for data logging, chart recording, or
display purposes only. Also, where provided, speed alert setpoints are suitable for annunciation
purposes only.
Magnetic pickups may not be used for the reverse rotation option because these transducers do not
provide a clean edge for the detection circuit during low speeds. This could lead to false indications
of rotation direction.
Magnetic pickups are not recommended for the zero speed option because these transducers do not
provide a clean edge for the detection circuit during low speeds.
Failure to take the above items into account constitutes a misuse of the product and may result in
property damage and/or bodily injury.

Note: The Bently Nevada product line does supply an Overspeed Protection System for the 3500
System. Consult Specification and Ordering Information part number 141539-01.




Specifications and Ordering Information
Part Number 141538-01
Rev. B (03/07)

Page 2 of 9
Specifications
Inputs
Signal:
Each Tachometer Module accepts
up to 2 transducer signals from
proximity probe transducers or
magnetic pickups. The input
signal range is +10.0 V to -24.0 V.
Signals exceeding this range are
limited internally by the module.
Input
Impedance:
20 k (standard);
40 k (TMR);
7.15 k (Internal Barrier).
Power
Consumption:
5.8 watts, typical.
Transducers:
Accepts 1-2 proximity transducer
signals.
Note: Restrictions may apply to magnetic
pickups. Refer to the Application Note
(page 1).
Outputs
Front Panel
LEDs
OK LED:
Indicates when the Tachometer
Module is operating properly.
TX/RX LED:
Indicates when the Tachometer
Module is communicating with
other modules in the 3500 rack.
Bypass LED:
Indicates when the Tachometer
Module is in Bypass Mode.
Buffered
Transducer
Outputs:
The front of each module has one
coaxial connector for each
channel. Each connector is short
circuit and ESD protected.
Buffered outputs are available at
the I/O module via Euro style
connectors.
Output
Impedance:
550 .
Transducer
Power Supply:
24 Vdc, 40 mA maximum per
channel.
Recorder:
+4 to +20 mA. Values are
proportional to module full-scale
range (rpm or rpm/min). Individual
recorder values are provided for
each channel. Monitor operation
is unaffected by short circuits on
recorder outputs.
Voltage
Compliance
(current output):
0 to +12 Vdc range across load.
Load resistance is 0 to 600 .
Resolution:
0.3662 A per bit ±0.25% error at
room temperature ±0.7% error
over temperature range. Update
rate approximately 100 ms.
Signal Conditioning
Specified at +25 ºC (+77 ºF).
Speed Input:
The 3500 Tachometer will support
0.0039 - 255 events per revolution
with a maximum full scale range
of 99,999 rpm and a maximum
input frequency of 20 kHz.
Minimum input frequency for
proximity transducers is 0.0167
Hz (1 rpm for 1 event/revolution)
and for passive magnetic pickups
is 3.3 Hz.

RPM Accuracy:
Less than 100 rpm = ± 0.1 rpm,
Specifications and Ordering Information
Part Number 141538-01
Rev. B (03/07)

Page 3 of 9
100 to 10,000 rpm = ±1 rpm,
10,000 to 99,999 rpm = ± 0.01%
of true shaft speed.
RPM/Min
Accuracy:
± 20 rpm/min.
Transducer Conditioning
Auto Threshold:
Use for any input above 0.0167
Hz (1 rpm for 1 event/revolution).
Minimum signal amplitude for
triggering is 1 volt peak-to-peak.
Manual
Threshold:
User selectable from +9.5 Vdc to -
23.5 Vdc. Minimum signal
amplitude for triggering is 500
millivolts peak-to-peak.
Hysteresis:
User selectable from 0.2 to 2.5
volts.
Alarms
Alarm
Setpoints:
Alarm 1 levels (setpoints) can be set for each value
measured by the Tachometer. In addition, Alarm 2
setpoints can be set for any two of the values
measured by the Tachometer. All alarm setpoints are
set using software configuration. Alarms are
adjustable and can normally be set from 0 to 100%
of full scale for each measured value.
Alarm Time
Delays:
Alarm delays can be programmed
using software, and can be set as
follows:
Alarm 1:
From 1 to 60 seconds in 1 second
intervals.
Alarm 2:
From 1 to 60 seconds in 0.1
second intervals.
Proportional Values
Proportional values are speed measurements used
to monitor a machine. The Tachometer Module
returns the following proportional values:
Rotor Speed
Speed*,
Speed Band
Peak Speed**
Rotor
Acceleration:
Rotor Acceleration*,
Speed,
Peak Speed**
Zero Speed:
Zero Speed*,
Speed, and
Peak Speed**
Reverse Rotation:
Reverse Speed*,
Reverse Peak Speed,
Speed (forward),
GAP**, and
Num Reverse Rotations
* The primary value for the channel. This value can
be included in contiguous registers in the
Communications Gateway Module.

** This proportional value is for display and setup
purposes only. No alarming is provided.
Environmental Limits
Operating Temperature:
When used with Internal/External
Termination I/O Module:
-30 ºC to +65 ºC (-22 ºF to +150
ºF)
When used with Internal Barrier
I/O Module (Internal Termination):
0 ºC to +65 ºC (32 ºF to +150 ºF)
Storage
Temperature:
-40 ºC to +85 ºC (-40 ºF to +185
ºF).
Specifications and Ordering Information
Part Number 141538-01
Rev. B (03/07)

Page 4 of 9
Humidity:
95%, non-condensing.
CE Mark Directives
EMC Directives:
EN50081-2:
Radiated Emissions
EN 55011, Class A
Conducted Emissions
EN 55011, Class A
EN50082-2:
Electrostatic Discharge
EN 61000-4-2, Criteria B
Radiated Susceptibility
ENV 50140, Criteria A
Conducted Susceptibility
ENV 50141, Criteria A
Electrical Fast Transient
EN 61000-4-4, Criteria B
Surge Capability
EN 61000-4-5, Criteria B
Magnetic Field
EN 61000-4-8, Criteria A
Power Supply Dip
EN 61000-4-11, Criteria B
Radio Telephone
ENV 50204, Criteria B
Low Voltage
Directives:
EN 61010-1
Safety Requirements
Hazardous Area Approvals

CSA/NRTL/C
Approval Option
(01)
Class I, Div 2
Groups A, B, C, D
T4 @ Ta = -20 °C to +65 °C
(-4 °F to +150 °F)
Certification
Number
CSA 150268-1002151 (LR 26744)
Approval Option
(02)
When used with I/O module
ordering options with internal
barriers:
A/Ex nC[ia] IIC
Class I, Zone 2/(0)
Class I, Div I, Groups A,B,C,D
T4 @ Ta = -20 °C to +65 °C
(-4 °F to +150 °F)
Certification
Number
CSA 1389797 (LR 26744-211)

ATEX
Approval Option
(02)
For Selected Ordering Options
with ATEX/CSA agency
approvals:
II 3/(3) G
EEx nCAL[L] IIC
T4 @ Ta = -20 °C to +65°C
(-4 °F to +150 °F)
Certification
Number
LCIE 04 ATEX 6161X
Note: When used with Internal Barrier I/O
Module, refer to specification sheet
141495-01 for approvals information.

Physical
Monitor Module
(Main Board)
Dimensions(Height x
Width x Depth):
Specifications and Ordering Information
Part Number 141538-01
Rev. B (03/07)

Page 5 of 9
241.3 mm x 24.4 mm 241.8 mm
(9.50 in x 0.96 in x 9.52 in).
Weight:
0.82 kg (1.8 lb.).
I/O Modules
(non-barrier)
Dimensions (Height
x Width x Depth):
241.3 mm x 24.4 mm x 99.1 mm
(9.50 in x 0.96 in x 3.90 in).
Weight:
0.20 kg (0.44 lb.).
I/O Modules
(internal
barrier)
Dimensions
(Height x Width
x Depth):
241.3 mm x 24.4 mm x 163.1 mm
(9.50 in x 0.96 in x 6.42 in).
Weight:
0.46 kg (1.01 lb.).
Rack Space Requirements
Monitor Module:
1 full-height front slot.
I/O Modules:
1 full-height rear slot.
Ordering Considerations
General
If the 3500/50 Module is added to an existing 3500
Monitoring System, the following (or later) firmware
and software versions are required:

3500/20 Module Firmware
Revision G (1.07)
3500/01 Configuration Software
Version 3.50 or later for Reverse
Rotation
Version 2.00 or later for other
types
3500/02 Data Acquisition
Software
Version 2.40 or later for Reverse
Rotation
Version 2.00 or later for other
types
3500/03 Display Software
Version 1.40 or later for Reverse
Rotation
Version 1.10 or later for other
types
3500/50 Firmware
Revision J (1.09) or later for
Reverse Rotation
External Termination