implementation of inductive sensor.

hola a todos. here in trouble, hope you can help me.

i was asked to monitor t speed (rpm) of an axis. i have a pulse counter, and i have inductive sensor.. until that point everythings ok. t problem is that i dont have any cogwheel or protuberance to generate t pulses. i have seen some cogwheels which are made of 2 halfs which couple each other arround the axis and that way you have a cogwheel mounted on that axis. that is what i want to do but..
i have not found those cogwheels anywhere (here in town, on the web..) do i have to look for a CNC guy to do it or is there any commercial brand for these?

thanks for your help.

A very cheap crude pusle counter can be made by welding (or bolting) a piece of metal onto the rotating shaft, so that it can be seen by your inductive sensor.

In a bind, I have used a piece of steel bar stock, 1" wide x 1/8" thick and long enough to create a taget for my proximity switch. Then in my PLC, I set up two timers, one to measure the prox switch ON time, and one to measure the same prox switch OFF time. Each time the prox switch goes ON, you can count 1 revolution per TIME (with TIME = accumulated values of ON timer + OFF timer), but if either timer reaches its Preset Value, then it means the shaft has stopped turning (either prox switch does not see target for long time, or it sees it all the time), so don't allow any more RPM counts.

Here is a LogixPro PLC program for the above RPM counter and alarm. 120 RPM is the fastest that my LogixPro program will sense a change in the Input switch. This simulates the typical problems seen with using real prox switches to measure RPM.

Remove setscrew from gear, and replace with a long socket head screw. Use head of screw to trigger a prox.

Red Lion has a bunch of the split type "gears" for use with prox switches in their catalog I believe.

Take old gear saw in half bore out the center to shaft dia and if a slow moving shaft where you dont need to worry about balance tack weld in place. High speed shafting I would not do this.

Do not forget anything with teeth will work - have seen done on chain drives
Dan Bentler

Do not forget anything with teeth will work - have seen done on chain drives

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Yes, at low speeds. The more "teeth" (targets) your prox switch must see on each revolution, the lower RPM it can successfuly monitor. Only 1 tooth allows reading higher speeds, because your switch only has to be fast enough to switch twice per revolution. If you have 10 cogs, it has to switch 20 times per revolution and the speed limit is much lower. Of course, using 1 tooth means poor accuracy at very low speeds. As always it is a trade off between accuracy and speed.

thanks everyone for their replys.

at t end, i used a "split-type" gear and its working fine.