Extech Instruments 461920 User manual

USER GUIDE
Model 461920
Laser Photo Tachometer

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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.
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 care.
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.
Laser complies with: FDA 21 CFR 1040.10 and 1040.11, IEC 60825-1 (2001-2008) Edition 1.2
EN 60825-1:1994/A11:1996/A2:2001/A1:2002

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Meter Operation
RPM Measurement Mode
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 straight on 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 set the units to RPM, 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.
COUNT Mode
1. Apply an appropriately (0.5”/12mm) sized square piece of reflective tape to the surface of the
object under test. Note: Reflective tape may not be necessary.
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 set the units to 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 the last count (REV) from the last
measurement period.
Measurement Notes
1. Bright ambient light may interfere with the reflected light beam. Holding the tachometer closer to
the target or 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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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.
You, as the end user, are legally bound (Battery ordinance) to return all used batteries and accumulators;
disposal in the household garbage is prohibited!
You can dispose of your used batteries / accumulators at collection points in your community or wherever batteries /
accumulators are sold!
Disposal: Follow the valid legal reulations with respect to the disposal of the device at the end of its lifecycle
Specifications
Time base Quartz crystal
Display 5 digit LCD display
Laser light source Class 2 laser < 1mW power; Wavelength is 630 to 670nm
Detecting Distance 2 to 20" (50 to 500 mm)
Sampling Time 0.5sec (over 120 rpm)
Tachometer accuracy ± (0.05% reading + 1digit)
Memory Last reading and MIN/MAX readings
Operating Conditions 32 °F to 122 °F (0 °C to 50 °C); RH 80% Max
Power Supply Internal 9V battery or external AC Adaptor (6 to 9VDC)
Power Consumption 45mA DC approx.
Weight 5.3oz. (151g)
Size 6.3x2.3x1.6" (160x58x39 mm)
Range Specifications
Range Resolution Accuracy (%reading)
Photo Tachometer 2 to 99,999 rpm 0.1 rpm (<1000rpm)
1 rpm (>1000 rpm) ± (0.05% + 1d)
Counter 1 to 99,999 REV 1 count ± 1 count
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