This is a useful item. I have the Cermark and it has been flawless for around 7 years. Uses a 9v alkaline and can read RPM from a foot away in bright light.
Re: Aircraft Tacho
Aug 30, 2003
28 Replies
I recently bought a Thunder Tiger jobby for about £25.00. In good sunlight work from about 6 inches, seems to produce consistent numbers and does both
2 and 3 bladed props. Runs off a 9V PP3. Happy with it for the money. Only thing I have noticed it it doesnt work well under lights that have dimmer switches on, why i dunno, but claims 3100 despite my zagi doing closer to 17K! But in natural light it faultless. Got it from Als hobbies, but dunno if they are they cheapest place...
It won't work under artificial lights because they aren't a constant source. They are actually flickering to the beat of the electrical frequency!
Isnt a way to check an optical tacho for accuracy to point it at a flourescent tube?? It should read 3000 i believe.
John.
Don't get the hobbico one. It runs on 4 watch batteries, and if you forget to turn it off overnight, in the morning you have to buy new batteries. About $14 worth. I did this twice before I ripped it apart and made a connector so it would run off a reciever pack which I could recharge.
3000 un the UK and other places outside the US. 3600 in the US.
I was referring to the fact that he couldn't read the prop RPM under artificial light.
In the US, 60HZ flickers 3600 times per minute [60 * 60]
John.
TNC makes the best tach on the market.
opinions will vary, jk
actually, the light flickers at 7200 per minute, if your tach is set for 2 blade prop it will read 3600
bob
actually, the light flickers at 7200 per minute, if your tach is set for 2 blade prop it will read 3600
bob
================================================ I guess that would be true. I just knew my Globe teach reads 3600 in my garage.
Mine runs on 2 AAA batteries - they must have learned a lesson about battery costs.
David
All they had to do was put in a 5 minute auto shutoff, for idiots like me.
Fairly sure John is in the UK.
*Very* roughly, North/Central/South America (but not Argentina, Chile), Western Japan use ~110v, 60Hz Europe, Asia, Africa, Australasia use ~220v, 50Hz
Actually, you got themaths wrong. 50hz x60 seconds time TWO PULSES PER CYCLE= 6000, but tachos expect TWO bladed props, so right answer, wrong maths :-)
60 hz flickers at double that. The bulbs - or neons - light up twice per cycle.
The flicker frequency is actually 120Hz
Europe is standardising on 230V 50Hz, but currently have 220,230 and
240. All countries are all theoretically moving to 230, I say theoretically because we actually have tolerances wide enough to allow countries to stay exactly where they are if they wish, now there's a diplomatic solution for you 8-). New products have to cope with the range so it's all academic really.Greg
But what would idiots do with idiot-proof stuff
David
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