Extech Instruments 461891 User manual

User’s Guide
Contact Tachometer
Model 461891
•Measures from 0.5 to 19999 rpm
•Min/Max Memory Recall
•Cone, funnel, surface attachments included
•Quartz crystal time base

461891 Ver. 1.9 7/02
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Introduction
Congratulations on your purchase of Extech’s Digital Tachometer. This professional meter,
with proper care, will provide years of safe reliable service.
Specifications
General Specifications
Circuit Custom one-chip LSI microprocessor circuit
Time base Quartz crystal
Display 5-digit multi function LCD display
Measurements Rotation Speed 0.5 to 19,999 rpm
Surface Speed 0.2 to 6560 ft/min.
0.05 to 1999.9 m/min
Memory Last and Max/Min readings
Sampling Time 1 second
Operating Temperature/RH 32 °F to 122 °F (0 °C to 50 °C) / <80% RH
Power Supply 4 x 1.5V AA batteries
Power Consumption Approx. 10 mA
Weight 0.62 lb (280 g) including batteries
Dimensions 8.2 x 2.8 x1.5" (208 x 72 x 37 mm)
Accessories Cone rpm adaptor, funnel rpm adaptor, surface speed
test wheel, and carrying case
Range Specifications
Range Resolution Accuracy
rpm 0.5 to 19,999 rpm 0.1 rpm (0.5 to 999.9 rpm)
1 rpm (over 1000 rpm)
+ (0.05% rdg +1d)
@23+ 5oC
ft/min 0.2 to 6560 ft/min 0.1 ft/min (0.2 to 999.9 ft/min)
1 ft/min (over 1000 ft/min) ± (1% rdg + 1 digit)
m/min 0.05 to 1999.9 m/min 0.01 m/min (0.05 to 99.99 m/min)
0.1 m/min (over 100 m/min)

461891 Ver. 1.9 7/02
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Front Panel Description
1 Shaft with cone adapter attached
2 LCD display
3 Measure button
4 Function select switch
5 Memory button
6 Funnel adapter attachment
7 Surface wheel adapter attachment
Operation
RPM Measurement
a) Slide the Function Switch to the "RPM" position.
b) Install the appropriate RPM Adapter on the Shaft
c) Press the Measure button while lightly pressing the RPM adapter against the
central opening of a rotating shaft in proper alignment. Release the Measure
button when the display stabilizes (about 1 to 2 seconds).
Surface Speed Measurement
a) Slide the Function Switch to "ft/min" or "m/min"
b) Attach the Surface Speed Wheel to the Shaft
c) Press the Measure button and hold the surface speed wheel against the device
being measured. Release the Measure button when the display stabilizes.
Memory Recall
The last value and last max and min values obtained before releasing the Measure
button are automatically stored by the meter. These memorized values can be
displayed by pressing the Memory button as described below:
a) Press once and hold - the last value is displayed followed by the "LA" icon
b) Press again and hold - the maximum value is displayed followed by the "UP"I con
c) Press again and hold - the minimum value is displayed followed by the "dn" icon

Maintenance
Battery Replacement: When the low battery indication appears ("LO" on the display),
slide the battery cover off of the rear of the instrument, replace batteries with four 1.5V AA
batteries and replace the cover. Remove the batteries if the instrument will not be used for
a long period of time.
Cleaning: Use only a dry cloth to clean the plastic case.
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.
Warranty
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 [phone] 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
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