EXTECH 461995

User's Manual
Model 461995
Laser Photo / Contact Tachometer
Photo/ Contact
46 19 95
/ min m/ min
Congratulations on your purchase of Extech's Laser Photo/Contact Tachometer, Model
461995. This Tachometer provides contact/non-contact RPM and Linear Surface Speed
measurements. The laser pointer beam provides accurate long distance measurements for
photo tachometer measurements. This meter, with proper care, will provide years of safe
reliable service.
Use extreme caution when the laser beam is on
Do not point the beam toward anyone's eye
Be careful not to let the beam strike the eye from a reflective surface
Do not use the laser near explosive gases or in other potentially explosive areas
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. 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.
Copyright © 2002 Extech Instruments Corporation. All rights reserved
including the right of reproduction in whole or in part in any form.
Support Hotline (781) 890-7440
Tech support: Ext. 200; Email: [email protected]
Repair/Returns: Ext. 210; Email: [email protected]
461995 V1.3 7/02
General Specifications
Custom one-chip LSI microprocessor circuit
Time base
Quartz crystal 4.194 MHz
Reversible 5 digit 0.4" (10mm) LCD display
Laser light source
Less than 1mW; Class 2 red laser diode (645nm approx.)
Detecting Distance
2 to 79" (50 to 2000 mm) depending on ambient light and RPM
Last reading and MIN/MAX readings
Operating Conditions
32 °F to 122 °F (0 °C to 50 °C); RH 80% Max
Power Supply
4 x 1.5 V AA batteries
Power Consumption
20mA DC approx.
10.6oz. (300g) including battery)
8.5 x 2.6 x 1.5" (210 x 67 x 38 mm)
(4)1.5V batteries, reflective tape 24" [600mm], surface
speed/rpm rotating attachments, and carrying case
Range Specifications
10 to 99,999 rpm
0.1 rpm (<1000rpm)
0.5 to 19,999 rpm
0.1 rpm (<1000rpm)
0.1 ft/min (<1000ft/min)
0.2 to 6560 ft/min
Accuracy (%rdg)
± (0.05% + 1d)
1 rpm (>1000 rpm)
1 rpm (>1000 rpm)
± (1% + 1d)
1 ft/min (>1000ft/min)
0.05 to 1999.9 m/min 0.01 m/min (<100m/min)
0.1 m/min (>100 m/min)
461995 V1.3 7/02
Meter Description
Photo Tachometer sensor and laser source
LCD display
MEMORY button
Function switch
Contact tachometer rotating ring
MEASURE button
Battery compartment (rear)
461995 V1.3 7/02
Meter Operation
Reversible LCD Display
The 461995 LCD display indicates Photo Tachometer measurements in one direction and
Contact measurements in the opposite direction. This permits the user to easily read the
measurement digits in both measurement modes with the meter held in either direction.
Photo Tachometer Measurements (refer to diagram below)
1. Apply an appropriately sized square piece of reflective tape to the surface of the object
under test.
2. Move the Function switch to the PHOTO position.
3. Point the laser pointer end of the meter toward the device under test at a distance of 2"
to 79" (50 to 2000mm).
4. Press the Measure button (located on the right side of the meter) and align the laser
pointer beam with the reflective tape.
5. Verify that the Monitor Indicator appears on the upper left hand section of the LCD
when the object under test passes through the light beam.
6. Release the Measure button when the RPM reading stabilizes on the LCD.
7. If the rpm is under 50, 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.
NOTE: Bright ambient light may interfere with the reflected light beam. Shading the target
area may be necessary in some cases.
CAUTION: Rotating objects can be dangerous. Use extreme care.
Light source
and reflection
Photo Tachometer
Reflective tape
Rotating object
461995 V1.3 7/02
Contact Tachometer RPM Measurements
Move the Function switch to the CONTACT position.
Press the Measure button while lightly pressing the rotating ring against the center
opening of a rotating shaft.
3. Release the Measure button when the display stabilizes (approx. 2 seconds).
Linear Surface Speed (ft/min or m/min) Measurements
1. Slide the Function Switch to "SURFACE SPEED ft/min" or "m/min" position.
Install the surface speed attachment on the meter rotating ring.
Press the Measure button and hold the surface speed wheel against the device
being measured.
Release the Measure button when the display stabilizes (approx. 2 seconds).
MIN/MAX and Last Reading Memory Recall
The 461995 can record Maximum, Minimum, and Last Reading for the period of time the
Measure button is held. These stored values can then be read directly on the meter's
display. The memory will automatically clear after approximately 10 seconds of meter
inactivity. Access the memory data immediately after the measurements have been taken
as follows:
1. Press the Memory key once and hold it down: The Last Reading is displayed
followed by the "LA" icon.
2. Press again and hold: The Maximum value is displayed followed by the "UP" icon
3. Press again and hold: The Minimum value is displayed followed by the "dn" icon
Battery Replacement
The low battery indication appears as "LO" on the display. To replace the batteries, slide
the rear battery compartment cover off of the meter, replace the four 1.5V AA batteries,
and replace cover.
Calibration and Repair Services
Extech offers complete repair and calibration services for all of the products we sell.
For periodic calibration, NIST certification or repair of any Extech product, call customer
service for details on services available. Extech recommends that calibration be performed
on an annual basis to ensure calibration integrity.
461995 V1.3 7/02