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99 Washington Street
Melrose, MA 02176
Phone 781-665-1400
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
Back to the Extech 461830 Product Page
User's Guide
Digital Stroboscope Tachometer
Model 461830 and Model 461831
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX 781.665.0780 - TestEquipmentDepot.com
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Safety
This symbol, adjacent to another symbol or terminal, indicates the user must refer
to the manual for further information.
This symbol, adjacent to a terminal indicates that, under normal use, hazardous
WARNING: Do not look directly at the Strobe’s Xenon lamp or its reflector.
WARNING: This device causes moving objects to appear still. Take precautions against
accidental contact with moving objects.
CAUTION: Do not touch the flash tube.
voltages may be present
Model 461830/461831 Version 2.2 November 2003
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Specifications
General Specifications
Circuit
Exclusive one-chip LSI circuit with crystal time base
Display 4-digit (10,000 count; 0 to 9999) LED display
Measurement unit RPM (revolutions or rotations per minute) is the speed of the
Operating Temperature 32 to 122oF (0 to 50oC)
Operating Humidity < 80% RH
Power Supply 110VAC (461830) or 220VAC (461831) 50/60Hz ±10%
Power Consumption <25 watts @ 115V
Weight 2.2 lbs. (1kg)
Dimensions 8.3 x 4.8 x 4.8" (21 x 12 x 12cm)
Housing construction Impact resistant plastic with plastic lens and mirrored reflectors
Electrical Specifications
Measurement Range
Resolution 0.1 (<1000 RPM/FPM)
Accuracy ± (0.05% + 1 digits)
Sampling Time 1 second
Strobe Flash adjust range LOW: 100 to 1,000 RPM/FPM
Strobe Flash tube type Xenon lamp
Strobe Flash duration 60 to 1000 microseconds
Strobe Flash Energy 4 Watt-Seconds (Joules)
Strobe Beam Angle 80o
Strobe Flash Color White 6500oK
Notes: Replace the Xenon lamp when readings appear irregular. To prolong the Xenon lamp
life and ensure safe operation, please adhere to the following recommendations.
• A 30-minute use limit < 3000rpm and 5-minute use limit > 3000rpm exists. Do not use
the instrument for periods longer than specified otherwise damage to the instrument
may result.
• Always permit a 10-minute cool-down between cycles.
• Do not touch the Xenon flash tube.
moving device under test which equals the FPM rate (strobe
flashes per minute)
100 to 10,000 RPM/FPM
1 (1000 to 9999 RPM/FPM)
10 (10,000 RPM/FPM)
HIGH: 1000 to 10,000 RPM/FPM
Model 461830/461831 Version 2.2 November 2003
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX 781.665.0780 - TestEquipmentDepot.com
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Meter Description
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2
1. Xenon lamp
2. LED Display
3. Grip handle
4. COARSE adjust knob
5. FINE adjust knob
6. Power ON/OFF switch
7. Range Select Switch
8. AC power cord and jack
4
5
67
1
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Model 461830/461831 Version 2.2 November 2003
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Operation
Powering the instrument
1. Plug the supplied power cable into the instrument’s power cable jack.
2. Plug the other end of the cable into an appropriate AC power source. The Model
461830 requires 110VAC and the 461831 requires 220VAC. Do not plug the device
into an incorrect power source otherwise damage to the instrument will result.
3. Use the ON/OFF switch to turn the instrument on or off.
Speed (RPM) Measurements
1. Remove power to the device under test so that it is stationary.
2. Affix a reflective mark or place a small piece of the supplied reflective tape on the
device under test.
3. Point the Stroboscope’s beam toward the reflective mark.
4. Use the ‘FINE’ and ‘COARSE’ adjustment knobs to synchronize or "stop" the motion of
the reflective mark (read the ‘Display Notes’ section below).
5. Read the RPM value on the LED display.
Range Adjustments
1. While measuring, use the RANGE button to select the range as desired
2. The LOW range is used for measurements below 1,000 RPM. The HIGH range is used
for measurements above 1,000 RPM.
Model 461830/461831 Version 2.2 November 2003
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Display Notes for Speed Measurements
Care must be taken to ensure that the reflective mark is providing a 1:1 measurement.
Check that there is only one mark and not two, four, or more stationary marks on the object
under test.
Two or more stopped marks indicate a ‘harmonic’ measurement (2:1, 3:1, 4:1 etc.) and the
instrument will display double, triple, or quadruple the actual speed. A useful method of
avoiding harmonic measurements is to adjust the FINE/COARSE knobs until two images
(reflective marks) appear and then lower the flash rate (via COARSE/FINE knobs) until a
single, stationary image appears. This will be the actual speed.
In the example below, a rotating shaft is affixed with one piece of reflective tape. The
illustrations below represent several possible images that would appear when the strobe
beam is pointed to the shaft.
If more than one reflective mark appears (as in columns 3, 4, and 5 below) the image is
showing a ‘harmonic’. The bold column (column 2) shows the actual speed of the shaft.
Column 1 shows a harmonic whereby the actual speed is divided in half. Because of this, it
is good practice to adjust the ‘FINE’ and ‘COARSE’ knobs until you can see the ‘doubled
harmonic’ (Column 3) and then the ‘halved harmonic’ (Column 1) and then find the setting
in-between (Column 2 in bold).
Shaft speed 1000rpm 1000rpm 1000rpm 1000rpm 1000rpm
Strobe flash rate 500rpm 1000rpm 2000rpm 3000rpm 4000rpm
Visible reflective
marks
Note that the LED display has an AUTO RANGE INDICATOR (flashing decimal at the far
right) that appears when the readings are over 10,000 RPM. In these cases, multiply the
displayed reading by 10.
Visually inspecting a moving object (stop-motion)
When the speed of the moving object matches the flash rate of the stroboscope, the
moving object appears still. Measure the speed of a moving object as described in the
previous sections to obtain a stop-motion. Once stop-motion is achieved, the FINE adjust
knob is used to vary the viewing perspective of the object under test for visual inspection.
Important note on Test Durations
The Xenon lamp used in this instrument has time restrictions on usage. If the specified test
times and cool-off periods (shown in the table below) are not observed, damage to the
instrument can result and the life span of the lamp can be shortened.
< 3,000 rpm 30 minutes
> 3,000 rpm 5 minutes
1 1 2 3 4
RPM Max. Operating Time Cool-Off Time
10 minutes
Model 461830/461831 Version 2.2 November 2003
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
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FAX 781.665.0780 - TestEquipmentDepot.com
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