Question about tachs
 

Is it possible to use an optical tach with indoor lighting. I know flourescents are a problem, but can an incandescent or other type of lighting work? My shop is well ventilated with over 4000 cfm being pumped in and out though and exhaust system when I need it.

Thanks,

Lon

AC powered light
 

Any light powered from AC power will have a 60 cycle pulse which will affect the reading of the TACH. If you need to use a TACH indoors, use a high powered BATTERY operated spot light in front of the prop, and dim the house lighting as much as possible.

Question about tachs
 

Lon,

Get a TNC tach. They emit their own light. It will work on the workbench as well as in total darkness.

http://www.ulster.net/~tnc/tncweb.html

Mark M.

Question about tachs
 

Since I have an extra battery in the boat and also a 200,000 cp spot/flood light from same, I hooked them up in the shop and the tach works perfectly. I also checked out the TNC web site and will order one.

Thanks Robert and Mark for the info.

Lon

Question about tachs
 

Unfortunatly, the TNC tach will not work in total darkness. They will however work in a lower light situation than what the cheap tachs do.

A TNC Tach when pointed at a light bulb or fluorescent lamp will always show a very definite number. I cannot remember what it is on mine but I think it is 100. That is how the book says to check the calibration on them. You can use a regular flash light to check the rpm when using a TNC tach. The TNC tach has an amplified detector in it and works just fine after the sun gets behind a cloud or in the shade etc. But you must have a little non-pulsating ambient light. When I bench run my engines, I do it in the garage with the prop blast going out the opened garage door. The TNC tach works fine just by using the light relecting off the back side of the prop blades. It will work after the day begins to fade but it doesn't have an internal light and it will not work in total darkness.

When you use a flashlight, you do not have to let the tach see it through the prop blades. You can hold the flashlight and the tach together and let the relected light off the prop blades do the job.

Good luck

Jim

TNC TACHOMETERS
 

The TNC tachs are worth every dollar they cost. I have had a SENSITACH for almost six years now and just recently returned it to Tony to have the switch replaced. He installed the circuitry in a new case and repaired it so it is as good as new for $11.00 which included shipping. The TNC uses a photo diode, which is much more sensitive than the photo resistor used by the cheap tachs. On a sunny day, you can accurately read RPM from as far as 8 or 10 feet away with this unit. You can check the basic calibration by holding it near a fluorescent light. It will show 3600 on the 2-blade range and will show 2400 on the 3-blade range.
I hope this sheds some light on the subject.
Regards, Duane

[email protected]

TNC Tach
 

WOW! 8' to 10' away! With my present tach, I have to get closer to the prop than I really like. Plus getting a steady reading is not easy. I got to get me one of those!

Thanks,

Lon

Question about tachs
 

Jim,

Maybe your are correct about "Total" darkness. However, I mount the sensor for mine in the ductwork of my ducted fans. I have tached them in the late evening hours with no additional light. That is as close to total darkness as you can get and still start the engine. I must say, this is a great tool. Maybe, the fan version of the tach is different than the others. I got mine so long ago, I don't remember.

Mark M.

Question about tachs
 

Mark,

I know that long after sundown the tach will not work reliably in my garage. I don't fly models that late so I don't know about in the open.

I think that the fan models are different because of the number of fan blades on the fan. I don't know about the rest of it. To my knowledge, he still makes a fan model.


The TNC tach is far better than any other tach I have seen at the different flying fields I go to. I used to have a Glow Bee and the sun had to be out for it to work. You could get it to work a little darker if you had white tips on your blades and shined it at the tips.

Maybe the TNC would work in even darker conditions if you had white tips. You might be able to get a standard TNC to work on a ducted fan if you put white on two blades opposite each other?

Jim