I’ve been intending to pickup a tachometer for my small engine projects for some time, and I finally got around to it. I wanted a simple-to-use unit that was portable and easy to carry. This lead me to the “sirometer” otherwise known as a vibra-tach. The concept is simple – there’s an inner dial that is rotated by hand which is calibrated to a thin wire that is extended or retracted as the dial is turned.
To determine RPM of any machine with a rotating shaft, the unit is held against the equipment and the dial is rotated until the wire extends and begins to resonate or vibrate. The wire is extended until it reaches the point of widest resonation, with the dial indicating the resulting RPM.
This device is proven, easy to use and very accurate when applied correctly. The unit I purchased is made in Germany and offered under the Tecumseh brand with the Tecumseh part number visible in one of the photos. I picked mine up on eBay, though I believe they are available through most small equipment dealers and cost somewhere around $30.00, give or take a bit
Click on any of the photos to see an larger image.
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