TREND NETWORKS LT-880 User manual

LT-880
Laser Tachometer
Manual
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Manual
LT-880 Laser Tachometer
Topic Page
GENERAL INFORMATION
Introduction............................................................................................................................. 3
Specifications.......................................................................................................................... 4
OPERATING INSTRUCTIONS
Unpacking and Inspection....................................................................................................5
Input Power Requirements..................................................................................................5
Front Panel ...............................................................................................................................6
Safety Considerations............................................................................................................6
Block Diagram..........................................................................................................................7
OperationalConsiderations...............................................................................................8,9
WARRANTY INFORMATION
RepairInformation..................................................................................................................10
LimitedWarranty....................................................................................................................10

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Introduction
LT-880 Laser Tachometer
INTRODUCTION
The LT-880 Laser Tachometer is a hand-held, battery operated device that senses the passage
of reflective/non-reflective markings on a rotating or linearly translated piece of machinery in
order to determine the target’s rotational rate or its linear velocity. The sensing head is remote
from the electronics package and is fiber coupled. This permits measurement of objects in hostile
environments or in hard-to-get-to locations. The sensed change in reflectivity from black to
white generates a transition at its output. This TTL/CMOS compatible signal may be utilized by
a spectrum analyzer, computer or electronic counter in order to provide information concerning
vibration, angular or linear velocity of the machinery under test. The high speed of the unit, 40
KHz, coupled with its small spot size can provide high resolution measurements unattainable with
conventional incandescent source tachometers.
A six digit LCD display indicates the rate of passage of the white/dark areas of the encoder and
registers the results in units of revolutions per minute, (RPM), revolutions per second, (RPS),
or pulses per second (PPS). The reading is updated twice per second. The user may input the
number of pulses per revolution of the encoder for use in the subsequent calculations. They may
range from 1 pulse per revolution to 255 pulses per revolution.
The laser wavelength employed by the unit is 650 nm (visible reddish orange). The use of visible
light aids the user in targeting the optical system onto the measurement point of interest. It also
enables use of a small spot size so that high resolution encoders may be employed.
The LT-880 employs four AA Ni-Mh batteries that power the unit for up to ten hours of
continuous operation. It also can operate from a wall-mount type power supply/charger. The
charger has a fast charge rate that can charge the batteries to full capacity in about 2 hours.
The optical head is equipped with a five meter length of duplex fiber cable. Other lengths of
fiber can be provided up to several hundred meters in length. Right angle attachments are also
available.
The use of specially manufactured reflective optical encoders in unnecessary. Encoders may be
made with any CAD program and a laser printer on ordinary white copier paper.
FEATURES AND BENEFITS
• Remote Sensing of RPM and Angular Vibration
• No Special Reflective Tape Required
• Large 5 Digit LED Display
• Sensing rates to 40 000 PPS
• Ni-mH Powered with Fast Charger
• Measures RPM, RPS, PPS
• Entry of number of encoder sectors
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Specifications
LT-880 Laser Tachometer
SPECIFICATIONS
Units of measurement 4 Hz to 500 Hz ( Inner slots), 40 Hz - 5 KHz (outer slots)
Display (3 Slot) 0.6 inch diameter (15 mm), and
(30 Slot) 0.6 inch by 0.2 inch (15 x 4.5 mm)
Readout Accuracy Phase-Locked-Loop, Direct Digital Synthesis
Measurement Update Rate ±.0025 % of setting
Range (using white copier paper) 0.1 % peak to peak, 3 slot section, 1.0 % peak to peak, 30 slot section
Measurement Bandwidth < 3 seconds
Laser Wavelength TTL, CMOS Compatible Square Wave, 4 Hz to 5000 Hz
Laser Power TTL, CMOS Compatible Square Wave
Laser Spot Size Five Digit, high intensity green, 0. 5 “ high
Laser Beam Divergence < 10 ppm/C
Output Impedance .001 Hz
Standard Fiber Optic Cable Length .01 Hz
Standard Fiber Types 0.1 Hz, 1 Hz
Fiber Optic Connectors 9600 Baud, N-8-1, 3 wire
Batteries Supplied Standard 8-32 tapped holes, mounting rod and stand is provided
Charger Power Requirements 4.1 inch diameter
Charge Time 0 - 40 C
Optical Head Dimensions (mm) 4.5 “ H x 4.5 “ W x 2 “ D, 114 mm x 114 mm x 51 mm
Electronics Package Dimensions (cm) 2.7 “ H x 7 “ W x 9.1 “ D, 69 mm, 178 mm, 231 mm
Total Weight Coiled Cord 10 feet max length
Operating Temperature 95-260 VAC, 50-60 Hz, 15 VA Max

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Unpacking and Inspection
LT-880 Laser Tachometer
UNPACKING
The instrument is equipped with the following items: one Optical Head with a five meter
fiber optic cable, one Electronics package, operating manual and one power supply /
charger. Contact TREND Networks if any item is missing.
Carefully remove each item from its packaging. Take care to keep all optical surfaces such
as the ends of the optical fibers free from contamination. Do not remove the dust covers
until they are to be used.
INSPECTION
Prior to shipment this instrument was inspected and found to be free of mechanical and
electrical defects. Upon acceptance by the carrier he assumes responsibility for its safe
arrival. After unpacking, examine the unit for any evidence of shipping damage. Should
you receive this instrument in a damaged condition, apparent or concealed, it must be
noted on the freight bill or express receipt and signed by the carrier’s agent. Failure to
do so could result in the carrier refusing to honor the claim. Upon filing a claim TREND
Networks should be notified.
INPUT POWER REQUIREMENTS
The LT-880 is designed to operate from its internal rechargeable batteries and/or its
combination wall-mount supply/charger.
Do not operate the unit with batteries other than 2000 mA-Hr nickel-metal hydride
cells that are supplied. Do not operate the unit from the charger without the batteries
installed. Do not attempt to use chargers other than the one supplied. Failure to observe
these precautions may cause damage to the unit.
The batteries supplied can be recharged hundreds of times. They do not exhibit partial
discharge memory eects as do Nickel Cadmium cells.
The North American charger may be operated from 108 - 125 VAC, 50 - 60 Hz. European
supplies are equipped with continental European style power connectors and will operate
from 210 to 250 VAC, 50 Hz. Total power consumption is approximately 16 W when
charging fully depleted cells.

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Front Panel
LT-880 Laser Tachometer
FRONT PANEL
The front panel controls are quite simple. The Power switch alternately energizes and
de-energizes the unit. The charger will charge the batteries whenever it is plugged into
the unit and AC mains regardless of the ON/OFF state of the unit.
The Units switch changes the desired units of measurement to RPM, RPS, or PPS.
The Pulses per Rev button causes the unit to alternately enter or leave the pulse per
revolution set mode. In this mode, the user may use the Up and/or Down buttons to enter
the number of light/dark cycles for the encoder being used. The photo at left shows the
pulses per revolution being set to 128. After the desired number is selected, the Pulses per
Rev should be pressed again and the unit will return to the measurement mode.
The six LED enunciators serve the following functions: Signal - Indicates that transitions
are being detected by the optical head. Low Bat - When on, indicates the batteries are
discharged. Approximately 5 more minutes of operation are available after which the unit
will automatically shut down. Fast Charge - Indicates that the charger is supplying high
charging current to the unit. This lights whenever the battery charger is first plugged in.
It will automatically revert to trickle charge after a time dependent on the current charge
state of the batteries. RPM, RPS, or PPS indicate the current units of measurement.
Safety Considerations
This is a laser equipped device and emits sucient levels of optical radiation to be
considered potentially eye damaging. While emitting less power than the average laser
pointer, these common sense precautions should be observed.
NEVER look into the beam emitted from the optical head. DO NOT point the beam at
specularly reflecting (mirror like) surfaces. NEVER view the output radiation emitted
with optical instruments.
The specific optical characteristics of the emitted beam are as follows:
Beam diam. 2 mm, collimated
Wavelength - 650 +/- 10 nm
Pulse Duration - Continuous
Output power - less than 3 mW

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Block Diagram
LT-880 Laser Tachometer
Laser Tach
Block Diagram Fig .1
Laser Diode
Automatic Power
Controller
Trans Z
Amp.
40 dB
AGC Amp
Pk to Pk
Detector
Sig.
Det.
Lo Pass
Filter
Output
Ni-MH AA Cells DC-DC
Conv.
+5V
-5V
Low
Bat.
Det.
Comparator
TTL/Cmos
Micro Processor
LCD Display
Controls
Det.
Laser
Diode
650 nm
VLD ST Connector
ST Connector
3 mm jacketed
FO Cable
Selfoc Lens
in Ferrule
3 mm jacketed
FO Cable
Selfoc Lens
in Ferrule

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Operational Considerations
LT-880 Laser Tachometer
OPERATIONAL CONSIDERATIONS
The LT-880 Laser Tachometer should be operated as follows:
1. Connect the optical head to the electronics package . The small core fiber connects to
the Laser output port on the electronics package It is denoted by a reddish rubber ring
located behind the connector. There is a similar reddish rubber ring around the laser ST
receptacle. The large core fiber connects the Optical Receiver port on the electronics
package to the remaining port on the optical head.
2. Position the optical head such that the resting surface of the target to be measured is
approximately 13 - 125 mm from the output aperture of the optical head.
3. Depress the Power button located on the electronics package.
4. A 2 mm red spot from the laser will appear on the surface of the target. Position as
needed.
5. The BNC connector labeled Output will provide a TTL/CMOS compatible logic signal
proportional to the rate at which the encoder sectors pass in front of the optical head. The
signal is positive (or logic 1) when a reflection is detected.
6. Should the range be in excess of 125 mm or if the target is insuciently reflective, the
Signal annunciator will be extinguished.
7. Use the Units switch to select the desired units of measurement.
8. Press the Pulses per Rev button to verify that the PPr number is correct for the encoder
being used. If satisfied, press the button again to return to the measurement mode. To
change the setting, use the Up/Down push buttons to select the proper setting.
Ambient Light Levels: Normal fluorescent light levels are acceptable and do not interfere
with normal operation. Bright light on the target or directed at the optical head should be
avoided.
Optical Surfaces: Always keep the fiber optic connectors clean. Keep them in the
connectors or the caps supplied. The fiber connectors and the small lenses at the end
of the optical head may be cleaned with isopropyl alcohol and a clean optical tissue or
Kimwipe. Fiber optic cleaning swabs may be used if it is suspected that the internal fiber
optic connectors have become contaminated.
Fiber Optic Cable: Do not sharply bend or kink the fiber optic cable. Bend radius should
be kept to a minimum of four inches.

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Operational Considerations
LT-880 Laser Tachometer
Encoder Characteristics: - The LT-880 has been designed to operate without dependence
on special reflective tape or encoders. A encoder may be generated with almost any CAD
drawing program such as AutoCad, Fast Cad, or CadKey. The drawing should be printed
on a laser printer on white paper. The number of spokes is determined by the number of
pulses per revolution that is required (more pulses per revolution are generally better
in that higher order harmonics may be detected without sampling aliasing). The main
consideration is that the white spaces between the spokes by wide enough accommodate
the laser beam at the target distance being used. An example of a typical target is shown
below.
16 PPr Encoder
Orientation of beam to surface - The beam should always be at an angle to the plane
of the encoder. If the beam is perpendicular to the surface, specular reflections will
be introduced which will reduce the contrast of the light to dark areas and may cause
unstable measurements.
Sensor
Encoder Surface
Incorrect Orientation Correct Orientation
Sensor
Encoder Surface

Warranty and Repair Information
LT-880 Laser Tachometer
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WARRANTY AND REPAIR INFORMATION
REPAIR INFORMATION
Products manufactured by TREND Networks are designed and manufactured to provide
reliable performance. However, in the event that service is required, both telephone
technical assistance and factory repair services are available. Call [phone], e-mail
[e-mail] or visit our web site at https://www.trend-networks.com/
us/ for more information or to request an RMA number.
For IN-WARRANTY REPAIRS, call us to obtain a Returned Material Authorization number,
(RMA Number). All products are to be returned to TREND Networks with freight charges
pre-paid. Those products sent under warranty will be returned to our customers pre-
paid. We cannot be responsible for returned products that do not reference the TREND
Networks RMA number.
For OUT-OF-WARRANTY repairs, services are billable for both time and materials.
LIMITED WARRANTY
TREND NETWORKS WARRANTS THAT TO THE FIRST PURCHASER, FOR A PERIOD OF TWO
YEARS FROM THE DATE OF RECEIPT, THAT THIS PRODUCT (THE PRODUCT) WILL BE FREE
FROM DEFECTS IN MATERIALS AND MANUFACTURING. THE FOREGOING WARRANTY IS
THE ONLY WARRANTY, EXPRESS OR IMPLIED, GIVEN BY TREND NETWORKS, I.E., THERE IS
NO WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE. TREND NETWORKS HEREBY
DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY OTHER THAN THE WARRANTY IN THE
FIRST SENTENCE TO THE FULLEST EXTENT PERMITTED BY LAW.
THE SOLE AND EXCLUSIVE REMEDY UNDER THIS WARRANTY IS REPAIR OR REPLACEMENT
AT TREND NETWORKS’ OPTION OF ANY PRODUCT THAT PROVES TO BE DEFECTIVE IN
MATERIALS OR MANUFACTURING WITHIN TWO YEARS OF RECEIPT OF THE PRODUCT.
NOTE: THIS WARRANTY DOES NOT APPLY TO ANY PRODUCT WHICH HAS BEEN SUBJECT TO
MISHANDLING, MISUSE, OR SERVICE BY UNAUTHORIZED PERSONNEL OR TO ANY PRODUCT
WHICH HAS BEEN DAMAGED, MODIFIED, ALTERED OR TAMPERED WITH.
TO THE FULLEST EXTENT OF THE LAW, TREND NETWORKS DISCLAIMS ALL LIABILITY FOR
ANY OTHER DIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES ALLEGED TO BE CAUSED
BY A DEFECTIVE PRODUCT, I.E., TREND NETWORKS WILL NOT BE RESPONSIBLE FOR ANY
PERSONAL INJURY, PROPERTY DAMAGE OTHER THAN THE COST OF REPLACING THE
PRODUCT OR ANY OTHER MONETARY DAMAGE SUCH AS LOST WAGES OR PROFITS CAUSED
BY ANY USE, ATTEMPTED USE OR INABILITY TO USE THE PRODUCT. NOTE: BY USING THE
PRODUCT, YOU AGREE THAT REPAIR OR REPLACEMENT AT TREND NETWORKS’ OPTION
WILL FULLY SATISFY TREND NETWORKS’ WARRANTY OBLIGATION TO YOU, WHETHER IN
CONTRACT, TORT, NEGLIGENCE, STRICT LIABILITY OR OTHER APPLICABLE LAW.

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NETWORKS.
TREND NETWORKS North America
300 Roundhill Drive, Suite 1,
Rockaway, NJ 07866, USA
Tel. [phone]
[e-mail]
Specification subject to change without notice. E&OE
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MADE IN THE USA