Tachometer ?

[Kaiser2boy]

I know my truck has a governor to limit over reving but still I thought it might be neat to install a small 3 inch tach in the dash just for the fun of it.

I have looked all over for a small 24 volt tach that tops out at 3500 RPMs but have had no luck.
I thought I may even buy a 12 volt unit and just connect its power to one battery but I dont know how the signal side would handle whats comming off the distributor. I hate to put out $40 on an experiment and have it go pop the second I try it.

Anyone know if there is such an animal?
I did see one made by a company called Dixson that at first looked good but it required some sort of magnetic pulse generator as a sending unit. Oh yeah it was expensive also.

[Charles Talbert]

I know my truck has a governor to limit over reving but still I thought it might be neat to install a small 3 inch tach in the dash just for the fun of it.

I have looked all over for a small 24 volt tach that tops out at 3500 RPMs but have had no luck.
I thought I may even buy a 12 volt unit and just connect its power to one battery but I dont know how the signal side would handle whats comming off the distributor. I hate to put out $40 on an experiment and have it go pop the second I try it.

Anyone know if there is such an animal?
I did see one made by a company called Dixson that at first looked good but it required some sort of magnetic pulse generator as a sending unit. Oh yeah it was expensive also.

The best deal, all options spent is to use a self energizing tach. There are several versions available from Datcon; (Maxima Technologies). They require no electric power source to operate the tach, only power to the light source, which can be 12 or 24 volt. They require a magnetic sensor as a signal source. These are easy to install in the bell housing cover. Just drill a hole in the cover directly below the ring gear teeth and install a weld nut to screw the sensor into. Screw it in until the sensor contacts the gear teeth, then back it out just far enough that it doesn't make contact. It seals with and o-ring and a jamb nut, connect 2 wires directly to the tach + / - and you are done. These are available in both digital and conventional styles. They can be calibrated easily and are DEAD ON accurate throughout the entire range.

Using other types presents a problem in that there is no mechanical drive on the 230 as a mechanical power source, and the 24 volt system presents an issue with electronic tachs. Choices are broad with 12 volt units, but not 24.

[Gordon Maney]

The best deal, all options spent is to use a self energizing tach. There are several versions available from Datcon; (Maxima Technologies). They require no electric power source to operate the tach, only power to the light source, which can be 12 or 24 volt. They require a magnetic sensor as a signal source. These are easy to install in the bell housing cover. Just drill a hole in the cover directly below the ring gear teeth and install a weld nut to screw the sensor into. Screw it in until the sensor contacts the gear teeth, then back it out just far enough that it doesn't make contact. It seals with and o-ring and a jamb nut, connect 2 wires directly to the tach + / - and you are done. These are available in both digital and conventional styles. They can be calibrated easily and are DEAD ON accurate throughout the entire range.

Using other types presents a problem in that there is no mechanical drive on the 230 as a mechanical power source, and the 24 volt system presents an issue with electronic tachs. Choices are broad with 12 volt units, but not 24.

Neat! What on the flywheel will trigger this sensor? Do you have to attach something?

[Kaiser2boy]

Hmm, I guess I have the same question as Gordon.

[Charles Talbert]

Very simple

It is triggered by the movement of the ring gear teeth moving past it very close to the sensor tip. It has only a few thousandths of an inch air gap between the end of the sensor and the tooth tips. There is no contact, and no moving parts. I was amazed by how slick this thing works, the simplicity of it in general, and how accurate it was the first time we used one. We did it for the same reason Kaiser spoke about, because of the 24 volt system and no good pick up point. We use an infrared tachometer to set up engine RPM and governor adjustment. It's very simple to calbrate the self energized tach and synchronize the RPM's equally. Once this is done, accuracy is spot on every time you check it. You can install the set up and calibrate it in an hour or so if you have the right tooling.

[Gordon Maney]

If, as you seem to imply, there is no trigger device attached to the flywheel, then the circuitry must be able to recognize a repeating pattern. That is the only answer I can come up with.

[MoparFreak69]

I dont see how this could work and be accurate.
Couple things to consider, just on the engine I swapped into my Jeep, an LA/Magnum 5.2 conglomeration. There are 2 ring gear tooth counts available, depending on where the starter is located in the bell housing.
I would think for that to work you would need to have a tooth missing so that it could recognize the longer pulse, and therefore know when 1 revolution had been performed. Could probably work with half of a tooth removed, but I dont think I want to try to start my rig with either a half, or whole, tooth missing from the ring gear.

[Gordon Maney]

I dont see how this could work and be accurate.
Couple things to consider, just on the engine I swapped into my Jeep, an LA/Magnum 5.2 conglomeration. There are 2 ring gear tooth counts available, depending on where the starter is located in the bell housing.
I would think for that to work you would need to have a tooth missing so that it could recognize the longer pulse, and therefore know when 1 revolution had been performed. Could probably work with half of a tooth removed, but I dont think I want to try to start my rig with either a half, or whole, tooth missing from the ring gear.

Just minutes ago I was visiting with a friend of mine who is an electrical engineer specializing in controls. He said you likely had to program it by entering a tooth count.

[gusbratz]

I have been looking at these for a while now toying with putting it on my backhoe which is diesel, since it needs no ignition input. just works off of a little mag pickup. I wonder how accurete it is.
http://www.northerntool.com/shop/too...2901_200322901

[gusbratz]

i just read the reviews and it sounds like made in china junk...

[Charles Talbert]

Well all I can say to the doubting Thomas' is try it if you need an accurate tach, and don't have further options.

I'm not at all familiar with any such item offered by Northern, so I can't comment on that.

A little more detail on the Datcon's we have used and like so well. The sensors are designed to work with various tooth counts, but is a fairly wide spread. I don't recall just what the exact figures are on what we used, but purely as an example you might say the tooth count is from 120 -250 teeth.

The tach itself has a switch on the back with I believe 5 different positions. If your engine is idling along at 600 RPM, simply change the switch position until the tach displays the closest reading to 600. Then you go to a fine adjustment screw to tune the tach to the exact RPM. Just takes a few minutes.

On some of our Cummins engines, we have used tachs powered off the alternator, mechanically cable driven units, electric tachs powered by hall effect generators driven from a mechanical source; and none of these will touch the self energized tachs used with the mag sensors for ease of installation, simplicity, and above all, pin point dead on accuracy throughout the entire range.

What we have used is top of the line instrumentation; I can not speak pro or con for anything out there of this type that may be of lesser quality. As was mentioned already, there is obviously cheaper Chinese junk out there. I'd say don't attempt to base your like or dislike of this system if you are attempting to compare low quality junk to top quality instrumentation. You would need to compare apples to apples in order to get a valid comparision.

Honestly, this is the extent of my knowledge with it. We chose it because it was an only option for a tach on 1 project we did a while back. It worked out great as I've said. Maybe I should; but I have not tried to get more formally educated concerning the system simply because I've already seen it works and works well.

[Gordon Maney]

Well all I can say to the doubting Thomas' is try it if you need an accurate tach, and don't have further options.

I'm not at all familiar with any such item offered by Northern, so I can't comment on that.

A little more detail on the Datcon's we have used and like so well. The sensors are designed to work with various tooth counts, but is a fairly wide spread. I don't recall just what the exact figures are on what we used, but purely as an example you might say the tooth count is from 120 -250 teeth.

The tach itself has a switch on the back with I believe 5 different positions. If your engine is idling along at 600 RPM, simply change the switch position until the tach displays the closest reading to 600. Then you go to a fine adjustment screw to tune the tach to the exact RPM. Just takes a few minutes.

On some of our Cummins engines, we have used tachs powered off the alternator, mechanically cable driven units, electric tachs powered by hall effect generators driven from a mechanical source; and none of these will touch the self energized tachs used with the mag sensors for ease of installation, simplicity, and above all, pin point dead on accuracy throughout the entire range.

What we have used is top of the line instrumentation; I can not speak pro or con for anything out there of this type that may be of lesser quality. As was mentioned already, there is obviously cheaper Chinese junk out there. I'd say don't attempt to base your like or dislike of this system if you are attempting to compare low quality junk to top quality instrumentation. You would need to compare apples to apples in order to get a valid comparision.

Honestly, this is the extent of my knowledge with it. We chose it because it was an only option for a tach on 1 project we did a while back. It worked out great as I've said. Maybe I should; but I have not tried to get more formally educated concerning the system simply because I've already seen it works and works well.

Thank you. I felt it had to be calibrated in some way, and that is why I visited with my EE friend. You confirm there is a calibration.

It sounds like a great tachometer to use! Thank you for telling us about it.

[MoparFreak69]

Thank you. I felt it had to be calibrated in some way, and that is why I visited with my EE friend. You confirm there is a calibration.

It sounds like a great tachometer to use! Thank you for telling us about it.

You were right Gordon. From what Charles described you are basically telling it tooth count when you adjust it into the known base speed rating of the 600 RPMs he mentioned. It does sound like a great tool especially for a machine that may not utilize any electrical system. Think old hand crank diesel powered rig.

[Charles Talbert]

If you will look back at post #5; you will see I mentioned there that simple calibration was necessary. Just didn't have the time to address in further detail right then.

[Kaiser2boy]

Having worked with electronics for a long time I see how it would work. It is supremely simple. The pick up is probably a small magnet with a coil around it. The steel teeth passing by it cause the magnetic field to fluctuate up and down causing current to be induced into the coil and up to the Tach.
How it knows when it has been around once is another matter. But if it works THAT is what maters.
Thanks Charles. Oddly the Mfg is not all that far from me.