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  #1  
Old 07-13-2008, 05:31 PM
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Non-contact Photo Tachometer Test

In another thread one of the members ask if there was a tachometer that could be hooked up to his/her Mercedes as there was none in the dash instrument cluster.
I remembered that there were 2 types of remote tachometers that that I had used in the past; one type was a strobe tach and the other (I could not remember the name at the time) was a Photo Tachometer.
Back in around 1987 they bought a Photo Tachometer where I worked to set the high idle speed on diesel gen-sets. At that time they cost around $80.

The Photo Tach projects a laser beam of light on a reflective piece of tape that you stick on the object you want to take the rpms of and reflects it back to the meter.
I was curious as to the present cost and checked Ebay.
On Ebay I found a wide range of prices on this item and picked seller hakuna100 (97.7% (+) feedback) to buy one from $9.00+13.80 shipping from Hong Kong for a total of$23.78.
The item arrived in about 1.5 weeks in good condition. The item was as described in the ad. The only odd thing is it uses 3 AA batteries.
Easy to use. I stuck a piece of the reflective tape on the Crankshaft Damper of my Volvo diesel as there no tachometer or a better place to stick the tape. You do need a straight shot at the tape as the light beam is not going to bend around objects.

After starting the engine you press the TEST button and point the light at the tape. Hold it steady and release the TEST button. You have now recorded the rpms.
Press the MEM button to see the rpms displayed on the screen. Press test again to clear the display


Thats all there is too it.
It can be used on anything that you can get the tape to stick to and there is a clear path for the beam of light. Range (distance) is 50-500mm that the light beam has to be from the tape.



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Old 07-13-2008, 09:20 PM
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That would be nice, not only for vehicles that have no tach, but also to check those that do. There is factory equipment to check RPMs but unlikely that any of us have access to it and probably would cost more than $9.00 plus shipping!
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Old 07-13-2008, 09:37 PM
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I was suprised at the low price myself. But, the same unit is being sold by a lot of sellers at a whole bunch of different prices.
There is also a comibination unit that has the Photo Tach and an direct contact tack combined. With the direct contact you actually have to put the adapter against the rotating item you want the rpm of.
To save money on fuel I cut back the max IP fuel adjustment on my Volvo and lowered the idle speed as you see in the pic to 620rpm.
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Old 07-15-2008, 12:17 PM
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tape?

i seen one at northern tool for like 60$ my only question is the tape used is it special or is it just reflective duct tape?
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Old 07-15-2008, 01:33 PM
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Quote:
Originally Posted by argus445 View Post
i seen one at northern tool for like 60$ my only question is the tape used is it special or is it just reflective duct tape?
You get a little over a foot of tape with the unit. The piece I cut was maybe 3/8 of an inch. That much tape will be a lifetime supply for me with the exception that I loose things.
It is special tape but it looks just like reflective (white) safety tape used on cars. Also replacement tape is sold on Ebay and that places like as you said Northern Tool.
What surprised me is the wide differences in prices for what appears to be the same unit.
Mine came from an Ebay seller in Hong Kong but I was not called to pay any customs duty on the item; it just arrived with the regular mail.
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Old 07-15-2008, 05:56 PM
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I also have one of them in my toolbox with no complaints. Asian imports sliding by customs from the far east is due to change soon for americans I understand.
I have not read a 123 though. I imagine the best way would be to put the reflective tape on the perimiter of the damper and hold the counter vertically from below. The accuracy of these units is very good by the way.

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