User's Guide
Model 461920
Laser Photo Tachometer
Introduction
Congratulations on your purchase of Extech's Mini Laser
Photo Tachometer, Model 461920. This Tachometer
provides non-contact RPM and Revolution count
measurements. The laser pointer beam provides accurate
long distance measurements for photo tachometer
measurements. This meter is shipped fully tested and
calibrated and, with proper use, will provide years of
reliable service.
Warranty
EXTECH INSTRUMENTS CORPORATION warrants this
instrument to be free of defects in parts and workmanship
for one year from date of shipment (a six month limited
warranty applies to sensors and cables). If it should become
necessary to return the instrument for service during or
beyond the warranty period, contact the Customer Service
Department at (781) 890-7440 ext. 210 for authorization or
visit our website www.extech.com
Return Authorization (RA) number must be issued before
any product is returned to Extech. The sender is responsible
for shipping charges, freight, insurance and proper
packaging to prevent damage in transit. This warranty does
not apply to defects resulting from action of the user such as
misuse, improper wiring, operation outside of specification,
improper maintenance or repair, or unauthorized
modification. Extech specifically disclaims any implied
warranties or merchantability or fitness for a specific
purpose and will not be liable for any direct, indirect,
incidental or consequential damages. Extech's total liability
is limited to repair or replacement of the product. The
warranty set forth above is inclusive and no other warranty,
whether written or oral, is expressed or implied.
for contact information. A
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461920 V2.1V 5/07
Meter Description
1. Photo Tachometer sensor and laser source
2. MEASURE button
3. MEMORY button
4. MODE button
5. AC Power Adaptor
6. Battery compartment (rear)
CAUTION: Rotating objects can be dangerous. Use extreme
WARNING: Do not directly view or direct the laser
pointer at an eye. Low power visible lasers do not
normally present a hazard, but may present some potential
for hazard if viewed directly for extended periods of time.
care.
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461920 V2.1V 5/07
Meter Operation
1. Apply an appropriately (0.5”/12mm) sized square piece
of reflective tape to the surface of the object under test.
2. Point the meter toward the device under test at a
distance of 2" to 20" (50 to 500mm).
3. Press the Measure button (MEAS) and align the laser
light beam with the reflective tape.
( )
(
)
4. Verify that the (
) Monitor Indicator appears on the LCD
when the reflective tape passes through the light beam.
5. To change units (RPM or REV), release the MEAS
button and press the MODE button.
6. When the Measure button is released the last reading
will remain in the display for 5 to 10 seconds before the
Auto Power Off feature turns the meter off.
7. With the meter OFF, press the MEM (memory) button to
recall the MAX, MIN and LAST rpm values or the last
count (REV) from the last measurement period.
Measurement Notes
1. Bright ambient light may interfere with the reflected light
beam. Shading the target area may be necessary in
some cases.
2. The non-reflective are must always be larger than the
reflective area.
3. If the shaft or rotating object is normally reflective, it
must be covered with black tape or paint before the
reflective tape is applied.
4. To improve repeatability of low rpm measurements,
apply additional squares of reflective tape. Divide the
reading shown on the display by the number of pieces of
reflective tape squares to calculate the actual rpm.
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461920 V2.1V 5/07
Specifications
Time base Quartz crystal
Display 5 digit LCD display
Laser light source Class 2 laser < 1mW power;
Detecting Distance 2 to 20" (50 to 500 mm)
Sampling Time 0.5sec (over 120 rpm)
Memory Last reading and MIN/MAX
Operating Conditions 32 °F to 122 °F (0 °C to 50 °C);
Power Supply Internal 9V battery or external
Power Consumption 45mA DC approx.
Weight 5.3oz. (151g)
Size 6.3x2.3x1.6" (160x58x39 mm)
Range Specifications
Range Resolution
Photo
Tachometer
Counter
2 to 99,999
rpm
1 to 99,999
REV
Wavelength is 630 to 670nm
readings
RH 80% Max
AC Adaptor (6 to 9VDC)
Accuracy
(%rdg)
0.1 rpm
(<1000rpm)
1 rpm (>1000
rpm)
1 count
± (0.05% + 1d)
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461920 V2.1V 5/07
Battery Replacement
The low battery indication appears as “ " on the
display. To replace the batteries, loosen the two Philips
head screws securing the rear battery cover and lift the
cover off. Replace the 9V battery and replace cover.
Calibration and Repair Services
Extech offers repair and calibration services for the
products we sell. Extech also provides NIST certification for
most products. Call the Customer Service Department for
information on calibration services available for this product.
Extech recommends that annual calibrations be performed
to verify meter performance and accuracy.
Technical support: Extension 200; E-mail: support@extech.com
Repair & Returns: Extension 210; E-mail: repair@extech.com
Product specifications subject to change without notice
For the latest version of this User Guide, Software updates, and other
Extech Instruments Corporation, 285 Bear Hill Road, Waltham, MA
Support line (781) 890-7440
up-to-the-minute product information, visit our website:
Copyright © 2007 Extech Instruments Corporation
All rights reserved including the right of reproduction in whole or in
www.extech.com
02451
part in any form.
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461920 V2.1V 5/07
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