rockom

My Feedback: (2)

I heard something once about testing your tach by pointing it at a flourescent light source. Is this true? What should it read?

-Rocko

ec121

My Feedback: (2)

You can test a tach by pointing it at a light. It should read 3600rpm because the 60hertz frequency(cycles per second) is times 60sec. for revs per minute. Therefore, 60 x 60 = 3600.

ds1niblick

ec121 has the count right, the light however is pulsing 7200 times per minuite, once on the + half of the cycle once on the - half of the cycle. The reading is 3600 when the tach is set to two blades. Set the tach to thre blades and the reading goes to 2400.

mtthomps

My Feedback: (2)

The frequency of AC current going to houses in America is exceedingly accurate. They keep track of how many cumulative fractions of a cycle it is off by reference to the atomic clock in Colorado. This is how they determine how hard to run generation equipment. If the freq starts to sag, even by a fraction of a cycle over a period of time, they up the generation quantity to not only bring it back to exactly 60 hz, but they will clock it very slightly fast to catch up to where it is supposed to be, phase wise.

This is probablyu a lot more than y'all wanted to know. Sorry.

SDR-Hammer

True, but interesting. Learn something new everyday.

TexasAirBoss

My Feedback: (22)

Actaully, the tach should read 1.8 K revs. Two blimks for each rev because there are two blades on the prop.

rockom

My Feedback: (2)

Thank you for all of your input. It does read 3600 when set to 2-blade. I have the Intellitach. Works geat and the price was good.

-Rocko

ec121

My Feedback: (2)

ds1niblick has the right answers for the props. I was thinking more from the hertz angle than the pos/neg half cycle angle. Still works out as a way to check the calibration on your tach.
I work as an instrument/electrical technician in a powerhouse. It is interesting that our generators are pulled by the national grid when we are tied into it. The voltage is controlled by the excitation voltage applied to the generators, but the frequency is controlled by all the generators on the grid being in phase. Sort of like one big team of horses all pulling together and being pulled(by the frequency) at the same time.. If one tries to get out of step for some reason, its tie-in breaker controller will sense it and open up. That grid is why you can generate megawatts in Tenn. and sell them off the grid in California. Theoretically, one big happy grid family. :-)

mtthomps

My Feedback: (2)

Yup. It's like one huge phase locked grid.

JimRoss

Nightz, what ever method you use to check your tach, when you use it on your engine, For Gods' Sake do it from BEHIND the prop.
NEVER NEVER NEVER read your tach from in front of the prop.
NEVER NEVER NEVER reach across the prop to make mixture adjustments or any thing else. Do it all from behind. If you can't reach something from behind, shut the engine down, make the adjustment, and then restart.

If you care to see why, I'll be glad to show you the result of taching my G-38 from in front. Lost part of thumb at first knuckle, three other large deep cuts on hand, 100+ stitches, broken tach, broken airplane. Do I need to say or show more?????????

Don't make the same stupid mistake I did.