Omega Automobile Parts HHT21A User Manual

Where Do I Find Everything I Need for  
Process Measurement and Control?  
OMEGA…Of Course!  
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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 ‘AAsize 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  
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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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