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HHT21A
Laser Tachometer
M3942/0303
NOTES
Safeguards and Precautions
1. Read and follow all instructions in this manual carefully,
and retain this manual for future reference.
2. Do not use this instrument in any manner inconsistent
with these operating instructions or under any
conditions
that
exceed
the
environmental
specifications stated.
3. Making measurements in close proximity to rotating
equipment can be dangerous. Keep all loose clothiing
and hair away from exposed moving machinery.
Properly replace all machinery guards after
completing measurement.
4. The socket on the front of the instrument is for use
with a remote charger. Only use model R-5 (115 Vac)
or R-6 (230 Vac) rechargers to charge the instrument.
5. The HHT21A has a laser beam
AVOID EXPOSURE
LASER RADIATION IS EMITTED
FROM THIS APERTURE
light source. Do not view the
laser beam directly as it could be
hazardous to the eyes. Do not
point the laser beam into another
LASER RADIATION
AVOID DIRECT EYE EXPOSURE
PEAK POWER
WAVELENGTH
3mw
650nm
person’s eyes. Do not view the
laser beam with telescopic
devices.
CLASS IIIA LASER PRODUCT
6. With exception of replacing the batteries, this
instrument is not user serviceable. For technical
assistance, contact the sales organization from which
you purchased the product.
of the way. It may also be convenient to keep a spare supply of reflective
tape in the free area underneath this cover.
TABLE OF CONTENTS
The instrument will provide six to eight hours of continuous operation on a
single set of batteries, depending on the type used. The instrument is
provided with a built-in charging network, which works in conjunction with
the optional NiCad batteries. The optional recharger plugs into the single
jack located next to the optical lens at the front end of the instrument.
Fourteen to sixteen hours is required for a complete recharge. When the
battery voltage in the HHT21A is getting low, the display will blink
“LO BAT” to indicate that the batteries need to be replaced.
SPECIFICATIONS ................................................................1
OVERVIEW ..........................................................................2
OPERATION ......................................................................... 2
USING THE HHT21A WITH A REMOTE OPTICAL SENSOR
(HHT20-ROS) ........................................................................3
NOTE: Only use model R-5B (115 Vac) or R-6B (230 Vac) rechargers
with NiCad batteries. Do not attempt to charge non-rechargeable
batteries.
CALIBRATION AND SELF-TEST ..........................................3
ALWAYS DISPOSE OF BATTERIES INASAFE AND RESPONSIBLE
MANNER.
BATTERIES ..........................................................................5
CLEANING ...........................................................................5
CLEANING
To clean the instrument, wipe with a damp cloth using mild soapy solution.
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SPECIFICATIONS
This product is designed for indoor or outdoor use under the following
conditions (per IEC1010-1):
Remote/Internal
Switch
Speed Range:
Accuracy:
Resolution:
Display:
5 RPM to 100,000 RPM
± 1 RPM or .01% of reading
1 RPM
6-digit 0.45” high liquid crystal
Twice per second
Recharger Jack
Internal Optics
Lens
Display Update:
On-Target Indication: Target (Bullseye) on lower left of display
Operating Distance: Range: Up to 10 feet [3.1 m] from leading edge
of reflective tape
Angle: Up to 45° from perpendicular to leading
edge of reflective tape
Pistol grip trigger - may be locked on with latching
push-button for longer duration measurements
Auto hold of last measurement for 90 seconds
Visible laser light source
Figure 1 HHT21A-R
with Optional Remote Sensor (HHT20-ROS)
Power-On Switch:
CALIBRATIONAND SELF-TEST
Optical System:
The HHT21A SERIES is a crystal controlled digital instrument that requires
no calibration. However, the accuracy of the instrument can be checked at
any time by aiming it at an old style fluorescent light and observing 7200 ±2
RPM. In countries with 50 Hz. power line frequency, the display will read
6000 ±2 RPM.
WARNING:
AVOID EXPOSURE
LASER RADIATION IS EMITTED
FROM THIS APERTURE
Do not view the laser beam directly as it
could be hazardous to the eyes. Do not
point the laser beam into another person’s
eyes. Do not view the laser beam with
telescopic devices.
LASER RADIATION
AVOID DIRECT EYE EXPOSURE
PEAK POWER
WAVELENGTH
3mw
650nm
NOTE: The Tachometer will not correctly read on energy-efficient
CLASS IIIA LASER PRODUCT
fluorescent lights.
Time Base:
Crystal controlled
Power Source:
4 “AA” batteries; Recharger socket provided for
optional rechargeable batteries
BATTERIES
Recharger Input:
Temperature:
Humidity:
Max input 7.8 Vdc @ 50mA
41 °F [5 °C] to 104 °F [40 °C]
Maximum relative humidity 80% for temperature
up to 88 °F [31 °C] decreasing linearly to 50%
relative humidity at 104 °F [40 °C]
The HHT21A SERIES operates from four ‘AA’ size batteries which are
located under the hinged top of the instrument. To access these batteries,
grip the tapered cover at the optical lens end of the instrument and pull up.
The cover is hinged at the display end of the instrument and pivots fully out
4
1
Dimensions (LxWxH):6.13” x 3.25” x 1.75 “ plus 4.75” handle
When the trigger is released, the HHT21A will hold the last measurement
taken and display it for up 90 seconds.
[155.7 mm x 82.6 mm x 44.5 mm x 120.7 mm]
Weight:
1.25 lbs [0.57 kg]
On very small shafts, the HHT21A will work down to a reflective tape size
of approximately 1/8 inch [3.2 mm] square. However, with this small tape
size, it would be necessary to operate the instrument very close to the
rotating shaft and insure it is held steady. For normal operation, a tape size
of approximately 1/2 inch [12.7 mm] square or larger is recommended, and
on very large diameter shafts or for very high-speed applications, a larger
size piece of tape may be required. It is also recommended that the reflective
tape be viewed just slightly off the perpendicular. The HHT21A will
operate at angles from 0 to 45 degrees, but best results are obtained by
aiming the instrument at the reflective tape at approximately a 10 to 20
degree angle. This insures that only pulses from the reflective tape are
received by the instrument and minimizes the problem of interference from
a highly polished surface or varying ambient lighting.
OVERVIEW
The HHT21A SERIES combines the accuracy and safety of a non-contact
optical tachometer with the convenience and ease of operation of a pistol
grip instrument. The instrument provides non-contact measurement of
rotational speed to an accuracy of .01% of reading. It reads RPM directly to
the nearest RPM, and a ‘on-target’ indicator is provided to verify the
instrument is properly aligned on a target and receiving valid information.
OPERATION
The HHT21A measures rotational speed from a single pulse per revolution.
This pulse is supplied by marking the rotating shaft with a visible reflective
tape target. The HHT21A is equipped with a built-in laser light source
providing a bright red beam which is aimed at the reflective tape located on
the rotating shaft. The pulse from the reflective tape is received back
through a single lens reflex optical system and detected by a photocell
inside the instrument. The HHT21A then computes the rotational speed
and displays it to a resolution of 1 RPM.
USING THE HHT21A-R WITH A REMOTE OPTICAL SENSOR
The HHT21A-R version of the tachometer has a provision for using the
optional HHT20-ROS Remote Optical Sensor. In addition to the standard
built-in optics of the HHT21A SERIES, a 1/8 inch [3.5 mm] phone jack is
provided on the front panel of the Tachometer to accept a remote optical
sensor plug. A toggle switch on the optics panel selects internal or remote
operation.
To operate the instrument, simply aim it at the reflective tape while holding
it at a distance of 1 inch [25.4 mm] to 10 feet [3.1 m] making sure to observe
laser safety precautions. Squeeze the pistol grip trigger, and read the indicated
speed. The on-target indicator must be on. The display is updated up to
twice per second.
For applications requiring the remote optical sensor, move the Remote/
Internal switch to the remote position to disable the internal optics of the
Tachometer. When the trigger is pulled or latched, the remote optical sensor
can be used for measurements. The HHT20-ROS Remote Optical Sensor
operates 3 feet [0.9 m] and ±45° from the reflective tape.
For longer duration measurements, the trigger latch on the side of the pistol
grip handle can be depressed after pulling the trigger, and the instrument
may be mounted on the 1/4-20 threaded bushing at the base of the handle.
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