EXTECH 461750

User's Guide
Mini Photo Tachometer Model 461700
Mini Contact Tachometer Model 461750
Congratulations on your purchase of the Extech Tachometer.
The Model 461700 Photo Tachometer uses precision optics and reflective tape to
measure the RPM of rotating devices such as fans and gears.
The Model 461750 Contact Tachometer uses convex and concave attachments to
measure RPM. It also has a built-in wheel to measure the linear surface speed of moving
devices such as conveyors and treadmills. Careful use of this tachometer will provide
years of reliable service.
General Specifications
5-digit LCD Display
Range selection
Automatic range selection
Time Base
4MHz Quartz Crystal
Sampling Time
1 second (>60 rpm); >1 second (10 to 60 rpm)
Photo Tachometer Distance
2 to 12” (5 to 30cm)
Operating Temperature
32 to 122 F (0 to 50 C)
Operating Humidity
80% RH Max.
Power supply
9V Battery
Battery Life
40 hours (approx.)
Applicable standards
EN 50081-1/1992 (EN 55022)
461700: 4.9 x 2.0 x 1.3” (124 x 51 x 33mm)
EN 50082-1/1997 (EN 55024)
461750: 5.9 x 2.0 x 1.3” (150 x 51 x 33mm)
461700: 4.0 oz. (114g); 461750: 5.0 oz. (142g)
Range Specifications
10.000 to 99999 rpm
± (0.1% reading + 2 digits)
10.000 to 9999 rpm
± (0.1% reading + 2 digits)
(461700 Photo)
(461750 Contact)
Surface Speed
3.0000 to 6560.0 ft/min
1.0000 to 1999.9 m/min
± (1.5% reading + 2digits)
1.0000 to 5000.0 yds/min
461700 / 461750 Version 2.3 Mar 2004
Meter Description
RPM adaptor (461750 only)
Wheel for linear surface measurements (461750 only)
Adaptor shaft (461750 only)
Model 461700 optics
Hand Guard (461750 only)
Power ON/OFF and HOLD button
Unit of measure selection button (461750 only)
LCD Display
Alternate Power ON/OFF button
Note that the battery compartment is located
on the rear of the instrument
Display Description
Low Battery
Data Hold
Rotations per minute
Meters per minute
Feet per minute
Yards per minute
461700 / 461750 Version 2.3 Mar 2004
461750 Safety Precautions
The 461750 incorporates a finger guard for protection. However, care should be taken
when measuring surface speed to avoid injury.
1. Hold the meter firmly when touching the wheel or attachment to a moving object
2. Keep fingers behind the finger guard while taking measurements
3. Keep your eyes and attention on the measurement activity at all times
4. Do not attempt to record measurements while holding the meter to the moving object
(use the Data Hold feature to freeze the reading on the LCD; refer to the Data Hold
section of this manual).
Meter Power
Power ON / OFF
1. Press the triangular POWER HOLD button to turn the device ON. Alternatively, press
the button at the bottom of the meter (just under the LCD) which doubles as a power
on/off button. Two buttons are provided for easy reach at any holding angle.
2. Press and hold the triangular POWER HOLD button (or the alternate button) for
approx. 5 seconds to turn the device OFF.
Auto Power OFF
1. The meter turns off AUTOMATICALLY after 20 minutes.
2. For 461750 only: To disable this feature, turn the meter off. Then press and hold the
POWER and UNITS buttons until the meter turns on. Release the POWER button first
and the ‘n’ display icon will appear. This indicates that the feature is disabled.
461700 / 461750 Version 2.3 Mar 2004
RPM Measurements
461700 Photo Tachometer
1. Affix a small (1/4”) square of reflective tape to the surface of the device under test.
See rotating gear example diagram below.
2. Allow the device under test to turn at its normal rate.
3. Turn the meter ON.
4. Point the Tachometer’s sensor toward the reflective tape. Keep the sensor
perpendicular to the reflective tape for the best results. The distance from meter to
object can be up to 12” (30cm).
5. Read the RPM (rotations per minute) measurement on the LCD.
Reflective Tape: Point
meter sensor toward tape
Rotating Gear
Front view
461750 Contact Tachometer
1. Affix the convex (cone) or concave (funnel) attachment that best fits the application
to the meter shaft as shown below.
2. Turn the meter ON.
3. Use the UNITS button to select RPM (the display will reflect the selection).
4. Touch the attachment to the moving object and read the displayed measurement.
Touch the convex or
concave attachment
to the turning object
461700 / 461750 Version 2.3 Mar 2004
Surface Speed Measurements (461750 only)
1. Turn the meter on as described previously.
2. Touch the wheel to the moving object and read the measurement on the display. Refer
to diagram below.
3. Use the UNITS button to select the unit of measure: ft/min (feet per minute); m/min
(meters per minute); yds/min (yards per minute).
Touch wheel to moving belt
Data Hold Feature
After the meter is turned on, the POWER-HOLD button can be pressed and released to
activate Data Hold. Data Hold automatically freezes the displayed reading. While the
reading is held, the HOLD display icon switches on. Press the POWER-HOLD button again
to exit this mode.
461700 / 461750 Version 2.3 Mar 2004
Battery Replacement
When the 9V battery weakens, the low battery indicator appears on the LCD. To replace
the battery, open the rear compartment and exchange the battery. Be sure to replace the
compartment cover securely prior to meter use.
Meter Cleaning
Wipe the meter housing with a damp cloth only. Do not use any abrasives or solvents.
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.
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 on 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 at www.extech.com (click on ‘Contact Extech’ and go to ‘Service Department’ to request an RA
number). A 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.
Support Hotline (781) 890-7440
Tech support: Ext. 200; Email: [email protected]
Repair/Returns: Ext. 210; Email: [email protected]
Website: www.extech.com
Copyright © 2003 Extech Instruments Corporation.
All rights reserved including the right of reproduction in whole or in part in any form.
461700 / 461750 Version 2.3 Mar 2004