# Tachometer



## Bluwolf (Nov 8, 2020)

Saw this in a video. Are these things any good? Or is there a reasonably priced, easily installed alternative?

https://www.amazon.com/dp/B0756VGDTC/ref=cm_sw_em_r_mt_dp_XF84NF26E86SSR7DBS0K


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## Old man here (Nov 5, 2020)

Bluwolf said:


> Saw this in a video. Are these things any good? Or is there a reasonably priced, easily installed alternative?
> 
> https://www.amazon.com/dp/B0756VGDTC/ref=cm_sw_em_r_mt_dp_XF84NF26E86SSR7DBS0K


I have not used that brand but I use the Tiny Tach. They are more expensive but they work well:

Amazon.com: Tiny Tach TT2B Digital Hour Meter / Tachometer for Small Gas Spark Engine Motor by The ROP Shop: Automotive


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## tabora (Sep 6, 2018)

Another option if you like larger digits and a backlit display. I have several of these...








RacingPowerSports Backlit Digital Tach Tachometer Hour Meter ATV Boat Bike UTV | eBay


<p>RacingPowerSports Backlight Digital Tachometer and Hour Meter for 2 or 4 Stroke Gasoline Engines (Motorcycle, Marine Boat, ATV, Snowmobile, Generator, Mower, etc...)<br>Accumulate total running hours (TOT), recording partial running time (JOB), Customizable warnings and maintenance reminders...



www.ebay.com


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## Old man here (Nov 5, 2020)

tabora said:


> Another option if you like larger digits and a backlit display. I have several of these...
> 
> 
> 
> ...


Those are nice ones as well.


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## Airstreamer67 (Oct 3, 2020)

I don't need a tach on my conventional gensets. The Hertz meter tells me what the revs are. IE, 60H = 3600RPM. Higher or lower H = proportional RPM.

Inverter gensets won't work that way. They do require a tach if you want to know engine speed.


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## Bluwolf (Nov 8, 2020)

So what your saying is these things actually work pretty well? And they all seem to install basically the same way. I just didn't want to bother if they were junk.


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## tabora (Sep 6, 2018)

Bluwolf said:


> I just didn't want to bother if they were junk.


I would not have recommended junk. Nor would I have made repeat purchases.


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## Bluwolf (Nov 8, 2020)

tabora said:


> I would not have recommended junk. Nor would I have made repeat purchases.


I guess my statement was rhetorical. I know nothing about these and was surprised that something this relatively cheap and easy to install would actually do a good job. Thanks for that.


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## speedy2019 (Jan 29, 2019)

I have just bought 1 of these but haven't installed it yet, but apparently if you wrap it too many times around the cable, it gives false readings?


Amazon.co.uk


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## Old man here (Nov 5, 2020)

speedy2019 said:


> I have just bought 1 of these but haven't installed it yet, but apparently if you wrap it too many times around the cable, it gives false readings?
> 
> 
> Amazon.co.uk
> ...


If you get false readings, remove or add one wrap at a time.


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## Airstreamer67 (Oct 3, 2020)

I doubt the number of turns matters. I'm sure the instrument just needs to know when the plug fires so that it can tell you how many times it fires in a minute to derive the revolutions-per-minute or RPM.

The five-or-six turns around the plug is to make sure they get a good signal each time it fires. If it gets poor signals from the plug, the RPM readings will be too slow. And like it says, too many turns will encourage inducing "noise" in the signal and throw off the values.


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## speedy2019 (Jan 29, 2019)

So I have just installed 1 of these to my generator.... But I think its reading the RPM a littlle to high as its output is 50hz/230volts so it should be 3000rpm, but its reading 3170rpm?


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## Airstreamer67 (Oct 3, 2020)

Does the number of "tight" wraps make any difference in the reading?


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## speedy2019 (Jan 29, 2019)

Airstreamer67 said:


> Does the number of "tight" wraps make any difference in the reading?


Nope I have tried 5,4 and 2 wraps and its made no difference, it still says its running just under 3200rpm, but thats with no load at all. That shouldnt make any difference though, should it?

When it starts up from cold it reads about 3000rpm, but the readings increase as the engine warms up?


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## iowagold (Jan 22, 2020)

rpm is rpm.
so speed is the hz staying the same?

and think of the wraps as a tuned coil... or electrical choke.
the rpm fq read out can be tilted by other gen noise.


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## speedy2019 (Jan 29, 2019)

iowagold said:


> rpm is rpm.
> so speed is the hz staying the same?
> 
> and think of the wraps as a tuned coil... or electrical choke.
> the rpm fq read out can be tilted by other gen noise.


To get 50hz the engine needs to be running at 3000rpm but the techometer says its running as a little less than 3200rpm?


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## iowagold (Jan 22, 2020)

go by the hz speedy.
that is the best way...


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