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INSTRUCTION MANUAL
English / Espanola
Model 461895
COMBINATION CONTACT/PHOTO TACHOMETER
1. INTRODUCTION
Congratulations on your purchase of Extech's Combination Contact/Photo Tachometer,
Model 461895. The combination tachometer is a patented design providing contact and
non-contact RPM measurements. In addition, linear surface speeds can be measured in
ft/min. or m/min.
Features
Use of an exclusive micro-computer LSI-circuit and crystal time base offers high 0.05%
accuracy and fast measuring time
RPM measurements span wide ranges: 5 to 99,999 RPM for photo tachometer and 0.5
to 20,000 RPM for contact tachometer
Suppression of insignificant zeroes in large, 5 digit LCD display provides exact RPM
while saving battery power
Last value and last max/min readings can be automatically stored and recalled
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2. SPECIFICATIONS
2-1 General Specifications
Circuit Custom one-chip LSI microprocessor circuit.
Time base Quartz crystal
Display 5 digit, 10 mm (0.4") LCD display with function annunciation
Measurement Photo Tachometer - 5 to 99,999 rpm
Contact Tachometer - 0.5 to 19,999 rpm
Surface Speed - 0.2 to 6,560 ft/min
Surface Speed - 0.05 to 1,999 m/min
Memory Last value, last max. reading, last min. reading
Sampling Time Photo Tachometer - 1 sec. (over 60 rpm)
Contact Tachometer - 1 sec. (over 6 rpm)
Detecting Distance Photo Tachometer
Operating Temperature 32 °F to 122 °F (0 °C to 50 °C)
Power Supply 4x 1.5 V AA (UM 3) batteries
Weight 0.66 lbs. / 300g (including battery)
Size 8.5 x 2.6 x1.5 (215 x 65 x 38mm)
Accessories
2-2 Electrical Specifications
Measurement Range Resolution Accuracy (% rdg)
Photo
Tachometer
Contact
Tachometer
Surface
Speed
Surface
Speed
3. FRONT PANEL DESCRIPTION
5 to 99,999 rpm 0.1 rpm (0.5 to 999.9 rpm)
0.05 to 19,999 rpm 0.1 rpm (0.5 to 999.9 rpm)
0.2 to 6560 ft/min 0.1 ft/min (0.1 to 999.9 ft/min)
0.05 to 1999.9
m/min
3-1 Reflective tape
3-2 Signal light beam
3-3 Monitor indicator
3-4 Display
3-5 Measure button
3-6 Memory button
3-7 Function switch
3-8 Rotating ring
3-9 Circumferential speed ring
3-10 Battery compartment
50 to 150 mm (2 to 6 inches) depending on ambient light
Reflective tape (23"), cone and funnel rpm adaptor, surface
speed test wheel, and carrying case
1 rpm (over 1000 rpm)
1 rpm (over 1000 rpm)
1 ft/min (over 1000 ft/min)
0.01 m/min (0.05 to 99.99 m/min)
0.1 m/min (over 100 m/min)
3-1
3-2
3-3
3-4
3-6
3-7
3-8
3-9
+ (0.05% + 1 digit)
± (1% rdg + 1d)
3-5
3-10
2
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461895 V1.8 August 2001
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4. OPERATION
4.1 Photo Tachometer
a) Slide the Function Switch to the "rpm PHOTO" position.
b) Apply a 0.5 (12mm) square piece of reflective tape to the object being measured.
c) Press the Measure button and align the visible light beam with the object being
measured. Check that the Monitor Indicator lights when the reflective tape
passes through the light beam. Release the Measure button once the display
stabilizes (approx. 2 seconds). For best results, hold the meter's light source 6 12" from the object being measured (low ambient light recommended).
d) If the RPM measurement is less than 50, apply additional squares of reflective
tape (equidistant). Divide the reading shown on the display by the number of
reflective squares to get the actual RPM.
NOTE: Bright ambient light may interfere with the reflected light beam. Shading the
CAUTION: Rotating objects can be dangerous. Use extreme care when holding the
4.2 Contact Tachometer
4.3 Surface Speed Measurement
4.4 Memory Recall
5. BATTERY REPLACEMENT
5.1 The low battery indication appears as a "LO" on the display.
5.2 To replace the battery:
target area may be necessary in some cases.
meter near any such object.
a) Slide the Function Switch to the "rpm CONTACT" position.
b) Press the Measure button while lightly pressing the rotating ring against the
center opening of a rotating shaft. Release the Measure button once the display
has stabilized (approx. 2 seconds).
a) Slide the Function Switch to "SURFACE SPEED ft/min" or "m/min".
b) Affix the Surface Speed Wheel on the meter shaft.
c) Press the Measure button and hold the surface speed wheel against the device
being measured. Release the Measure button once the display has stabilized
(approx. 2 seconds).
When measuring, the last reading and last max and min values are automatically
stored before the Measure button is released. Recall the values by pressing the
Memory button the appropriate number of times (see below).
a) Press once and hold - the last value is displayed followed by "LA"
b) Press again and hold - the maximum value is displayed followed by "UP"
c) Press again and hold - the minimum value is displayed followed by "dn"
a) Loosen the screw on the battery cover (3-10, Fig. 1) and remove.
b) Replace with 4 x 1.5V AA batteries and replace cover.
3
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461895 V1.8 August 2001
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6. CALIBRATION / 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 insure calibration integrity.
7. WARRANTY
Copyright © 2001 Extech Instruments Corporation. All rights reserved
including the right of reproduction in whole or in part in any form.
Tech Support Hotlines
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461895 V1.8 August 2001
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