Bently Nevada 3500/50M Data sheet

3500/50M Tachometer Module

Datasheet

Bently Nevada Machinery Condition Monitoring

Description

The 3500/50M Tachometer Module is a 2-channel module that accepts
input from proximity probes or magnetic pickups to determine shaft
rotative speed, rotor acceleration, or rotor direction. The module
compares these measurements against user-programmable alarm
setpoints and generates alarms when the setpoints are violated.

The Tachometer Module is programmed using the 3500 Rack
Configuration software. The following configuration options are
available:

l Speed Monitoring, Setpoint Alarming and Speed Band Alarming

l Speed Monitoring, Setpoint Alarming and Zero Speed

Notification

l Speed Monitoring, Setpoint Alarming and Rotor Acceleration

Alarming

l Speed Monitoring, Setpoint Alarming and Reverse Rotation

Notification

141538 Rev. P

The 3500/50M Tachometer Module can be configured to supply
conditioned Keyphasor signals to the backplane of the 3500 rack for use
by other monitors. Therefore, you don't need a separate Keyphasor
module in the rack.

The 3500/50M Tachometer Module has a peak hold feature that stores
the highest speed, the highest reverse speed, or the number of reverse
rotations that the machine has reached. You can reset the peak values.

Bently Nevada offers an Overspeed Protection System
(Product 3701/55).

3500/50M Tachometer Module
Datasheet 141538 Rev. P

WARNING

PRODUCT MISUSE

Risk of personal injury or equipment damage.

Do not use the 3500/50M Tachometer Module
independently or as a component of a speed control or an
overspeed protection system because it does not provide
protective redundancy or the response speed needed for
reliable operation as a speed control or overspeed
protection system.

The analog proportional output is suitable for data logging,
chart recording, or display purposes only. Speed alert
setpoints are suitable for annunciation purposes only.

Magnetic Pickups:
Do not use magnetic pickups for the reverse rotation option
or zero speed option. Otherwise, false indications of
rotation direction may occur. The transducers do not
provide a clean edge for the detection circuit during low
speeds.

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3500/50M Tachometer Module
Datasheet 141538 Rev. P

module via Euro style connectors.

Specifications

Inputs

Signal

Input signal range

Input impedance 20 k Ω (standard)

Power
consumption

Transducers

Each 3500/50M Tachometer
Module accepts up to two
transducer signals from proximity
probe transducers or magnetic
pickups.

+10.0 V to -24.0 V

Signals exceeding this range are
limited internally by the module.

40 k Ω (TMR)

7.15 k Ω (Internal Barrier)

5.8 watts, typical

Accepts 1 to 2 proximity
transducer signals

Restrictions may apply to
magnetic pickups. See on

page 2.

Output
Impedance

Transducer
Power
Supply

Recorder

Voltage
Compliance
(current
output)

Resolution

550 Ω

24 Vdc, 40 mA maximum per channel

+4 to +20 mA

Values are proportional to module full­scale range (rpm or rpm/min).

Individual recorder values are provided
for each channel.

Monitor operation is unaffected by
short circuits on recorder outputs.

0 to +12 Vdc range across load

Load resistance is 0 to 600 Ω

0.3662 µA per bit ±0.25% error at room
temperature ±0.7% error over
temperature range

Outputs

Front Panel LEDs

OK LED Indicates when the 3500/50M

Tachometer Module is operating
properly.

TX/RX
LED

Bypass
LED

Buffered Transducer

Outputs

Indicates when the Tachometer Module
is communicating with other modules in
the 3500 rack.

Indicates when the Tachometer Module
is in Bypass Mode.

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

Update rate approximately 100 ms

Signal Conditioning

Specified at +25 ºC (+77 ºF)

Speed Input

The 3500/50M Tachometer
Module supports 1 to 255 events
per revolution for Rotor
Acceleration and Zero Speed
channel types.

All other channel types support

0.0039 to 255 events per
revolution.

All channel types support a
maximum full scale range of
99,999 rpm and a maximum input
frequency of 20 kHz.

Minimum input frequency for

3/12

3500/50M Tachometer Module
Datasheet 141538 Rev. P

proximity transducers is 0.0167
Hz (1 rpm for 1 event per
revolution).

Minimum input frequency for
passive magnetic pickups is 3.3
Hz.

RPM Accuracy Less than 100 rpm = ± 0.1 rpm

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

Manual Threshold

Hysteresis User selectable from 0.2 to 2.5

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.

User selectable from +9.5 Vdc to

-23.5 Vdc

Minimum signal amplitude for
triggering is 500 millivolts peak­to-peak

volts

Alarms

Alarm Setpoints

Alarm 1 levels (setpoints) can be
set for each value measured by
the Tachometer.

Alarm 2 setpoints can be set for
any two of the values measured
by the Tachometer.

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 1 Time
Delay

Alarm 2 Time
Delay

Programmable alarm delays for
Alarm 1 and Alarm 2

From 1 to 60 seconds in 1 second
intervals

From 1 to 60 seconds in 0.1
second intervals

Measured Values

Measured values are speed measurements used to
monitor a machine. The 3500/50M Tachometer Module
returns the following measured values:

1

Rotor Speed

Speed
Speed Band

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