Aetna HP6492 User's Manual
Contents
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3. PRECISION SENSITIVE DIGITAL TACHOMETER INSTALLATION INSTRUCTIONS Special Instructions for SM amp SH Versions Aetna Engineering Precision Sensitive Digital Tachometers are premium quality instruments They use LSI digital circuitry to provide an instrument guaranteed accurate to one RPM that never requires calibration and performs reliably in the marine environment The S_ version tachometers are supplied with a special ratio setting designed to operate from the signal provided from a mag pickup or other sensor which receives a particular number of pulses per revolution PPR from the rotating device to be measured The PPR ratio refers to the preset number of pulses the tachometer must detect for each revolution of the apparatus to be measured The SM version is rated for use between 28 and 90 PPR and the SH version is rated for use between 90 and 255 PPR The overall tachometer performance involves functions beyond the PPR ratio such as filter constants and signal sensitivity Therefore the correct version SM or SH must be used for the specific PPR ratio desired or satisfactory performance will not be realized The tachometers are available with either Light Emitting Diode LED Model 8402 or Liquid Crystal Display LCD Model 8905 readouts The LED is best suited for use in shaded sunlight while the LCD should be used in applications where the tachometer will be exposed to direct un
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6. ff off on 199 off off off on on on 250 on on off off 20 off off off off off 251 off 201 off off off off 252 on on on on off off 202 on on off off on off on off 253 off on 203 off off on off on on 254 on on off 204 on on off off on on off off 25 on Procedure Position the switches according to the table using a thin stylus such as the metal filler from a ball point pen Care should be taken to use only moderate pressure in actuating the individual switches to avoid damaging them Use of plenty of light and magnification can be helpful Switch 1 is on the left 8 on the right up is on and down is off
7. he shield connection through but do not connect it to anything but the engine Using a single wire and the engine ground is not recommended and will yield inferior results Diesel Sender Installation The Aetna Engineering Models 8910 8912 and 8922 are magnetically coupled senders which sense the passage of flywheel gear teeth or similar items They generates the electrical RPM signal used by the tachometer The 8910 8912 are housed in diameter by 16 threads per inch case while the 8922 is contained in a 5 8 by 18 threads per inch case Both the 8912 and 8922 have dual electrical outputs Note that some engines built offshore have metric sized sender mounting holes Although Aetna does not provide metric sized senders most metric mag pickup senders will satisfactorily drive Aetna tachometers The sender is installed by screwing it into a threaded hole on the flywheel bell housing or other housing It is screwed in until the end contacts the gear then backed off one half turn and secured position with the jam nut The sender is connected to the tachometer using two conductor twisted shielded wire as previously described This combination of tachometer and sender will register the engine speed accurately to within one RPM when the sender is driven at exactly the preset number of pulses per revolution rated on the tachometer Testing Reconnect the battery and turn the ignition on The display s
8. he raised trim ring if it is to be used If the trim ring is positioned so that it will collect water drill a 3 16 drain hole at the lowest point in the ring The clamp legs may be bent over or cut off to accommodate thicker panels O ring is included for use as a centering aid when installing the unit in 3 3 8 inch holes If the hole is tight roll the O ring back from the flange then insert the tach so that the O ring rolls into the hole as the tach is inserted For larger holes an Oaring type spacer may be made from a length of appropriate diameter wire Wiring During wiring it is recommended that the negative battery cable be removed from the battery or the master switch es turned off The tachometer has a grounded case and is for use on negative ground systems only an isolated case version is available for isolated or positive ground use Connect the Ground terminal to a point that is connected to the negative battery terminal Connect the 12V terminal to a point that is energized when the ignition is switched on typically a purple wire In most cases power and ground are available by wiring to the terminals on an adjacent temperature or oil pressure gauge A one amp fuse must be installed in series with the Pos wire in order to enable the internal surge protector function To use the Model 8402 on 24 volts connect a 30 ohm 25 watt resistor our Model 8924 in series with the 12V tachometer term
9. hould illuminate and show 0000 indicating power is reaching the unit Start the engine and verify that the display indicates engine RPM When the engine is cold and idling without load the right hand digits may seem to jump This is due to fluctuation in the engine speed and is pronounced because the readout displays variations as small as one RPM The RPM s should steady when the engine is warmed and operated above idle under a constant load Should the display continue to jump excessively check engine tuning look for a fouled injector or a fuel suction line air leak Contact the factory for more suggestions If the tachometer shows all zeros with the engine running check the signal wiring from the engine If the tachometer s digits fail to show at all the problem is in the power wiring to the tachometer and not in the signal wiring If the indicated RPM is in error check that the ratio select switches are set properly The tachometer includes special circuitry to minimize loran interference from the digital processor Nevertheless if a loran set is aboard it should be checked for interference by observing the loran SNR when the ignition is on without the engine running Be sure any interference isn t from an alarm buzzer or bell If interference is detected check the loran antenna amp ground or install a filter such as the MAR P5 from Marine Technology 562 595 6521 in the 12 volt power and ground leads to the tachomete
10. inal For 32 volts use a 47 ohm 25 watt resistor our Model 8932 Failure to use the appropriate ballast resistor may damage the Model 8402 tachometer The 12V terminal on the Model 8905 tach may be safely connected to 12 24 or 32 volt systems without a ballast resistor The Points Sig terminal connects the RPM information signal from the engine to the tachometer This connection should be made using stranded two conductor twisted shielded wire For multiple stations two or more tachometers may be connected in parallel Diesel engines have no ignition and therefore require a tachometer sender to generates the digital impulses required by the tachometer Traditionally a mechanically driven sender was mounted on the tachometer drive cable fitting on the engine Many newer engines do not have such a fitting and instead use a magnetic pickup A mag pickup is a device that senses the passage of gear teeth in a non contact manner It is screwed into a threaded hole in the gear housing and adjusted so that the clearance is approximately one half turn back from contact with the gear The two sender wires are connected to the signal and ground terminals at the tachometer using a twisted shielded cable Connect the two wires from the sender through the two twisted inner conductors Connect the shield to the engine block Do not connect the tachometer end of the shield If the signal is continued on to another tachometer carry t
11. off 4 off off off on off 109 off off on off 47 off off on off on on on on 110 off on on off on on on off 48 off off on on off off off off 111 off off on on 49 off off on off off off 112 off on on on off off off off 50 off off on on off off on off 113 off on on on off off off on 51 off off on off off on on 114 off on on on off off on off 52 off off on on off on off off 115 off off off 53 off off on off off 116 off on off off off 54 off off off on off nz off on on on off on off on 55 off off on on off on on on 118 off on on on off on on off 56 off oif on on on off off off 119 off on on on off on on on 57 off off off off 120 off on off off off 58 off off off off 121 off off off 59 off off on off on 122 off on on on on off on off 6 off off on off off 123 off on on on on off on on 61 off off off 124 off off off 62 off off on off 125 off on on off 63 off off on on on on 126 off on on on on on off 64 off on off off off off off off 127 off on on on on on on on 65 off on off off off off off on 128 on off off off off off off off 65 off on off off off off on off 129 off off off off off off 67 off on off off
12. r The tachometer is now ready to use No adjustment is ever necessary The circuitry employs a piezoelectric crystal to permanently maintain calibration On the Model 8402 the built in dimmer senses the ambient light and adjusts the display intensity for comfortable viewing When operated in bright light the case will feel warm to the touch This is normal and will not damage the unit provided the case temperature does not exceed 175 degrees The Model 8905 has internal backlighting provided by solid state lamps that do not require routine replacement The 8905 consumes less than one half watt and does not create significant heat A special anti fogging compound is applied to the inside of the glass during manufacture Internal fogging of the glass may be reduced by removing the ratio switch cap In cases of persistent fogging contact the factory for additional help No routine maintenance of the tachometer is required Clean the glass with a soft cloth The sensor end of the sender should be cleaned periodically of any accumulation of magnetic particles which can shunt the magnetic sensitivity The sender may be tested with an ohmmeter Measurement of the resistance on the leads should be between 100 and 1000 ohms During installation wiring can be verified by temporarily running a separate wire pair directly from the sender to the tachometer Limited Warranty Aetna Engineering warrants its tachometers to be free of defect
13. s in material and workmanship for a period of two years from the date of purchase as shown on the original consumers purchase receipt Warranty service will be provided free of charge if the unit is delivered to Aetna Engineering during the warranty period accompanied by original consumer proof of purchase Any transportation removal or reinstallation charges will be paid by the purchaser whenever incurred in connection with this warranty In absence of proof of purchase receipt the warranty period shall be two years from the date of manufacture This warranty does not apply to units subjected to misuse neglect accident incorrect installation wiring improper installation water damage or units used in violation of the installation instructions furnished by us This warranty excludes incidental consequential damages connected with failure or defect in the product Aetna Engineering products are not designed intended or approved for use on or involving aircraft or in hazardous locations This warranty gives you specific legal rights and you may have other rights which vary from state to state Aetna Digital Tachometers SWITCH SETTING INSTRUCTIONS For use by Factory Authorized Personnel Version SM Version SH PPR Switch Position PPR Switch Position a 52 iat 6 off on off on on off on on off off on on on off off off on off on on off on of
14. shaded sunlight Both are self illuminated for night viewing The tachometers are supplied with a choice of black or polished stainless steel bezel The black bezel tachometer includes a trim ring which can be optionally used as required to match existing instrumentation Aetna tachometers also fit perfectly inside both the round and square VDO Blue Line cases contact us for detailed instructions Mounting Select a mounting location where the tachometer may be easily read The front of the tachometer has a gasketed glass to metal seal making it suitable for use in locations exposed to rain and spray It uses only non ferrous materials so it can be located in close proximity to a compass without significantly affecting the compass nevertheless the compass adjustment should be checked after installation particularly because the removed tachometers may have been influencing the compass The unit may be installed in an existing standard 3 3 8 inch diameter hole It will fit holes up to 4 inches when used with the optional black trim ring If placing the tachometer under a protective glass cover be sure that it is adequately ventilated to keep the maximum temperature of the case below 175 degrees Fahrenheit Exceeding this case temperature may damage the tachometer Mount the tachometer using the clamp and hardware provided exposed locations it should be bedded down with a bead of sealant behind the flange Place the tach in t
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