Tachometers with hall proximity sensor question

Hi guys. Me again. I am at the end of my rope here. I have made all the sugessted wiring changes in all the possible ways,I removed the tach and sensor wires from the sleeve it was in with the other wiring,I have even held the sensor in my hand as @mksj sugested in post #104. This all while connected to the 12V power supply. It all gave the exact same result. 4 zeros when turned on,brief readings on the display when turning by hand and then it returns to zero by it's own when I stop. The sensor light flash when it goes by the magnet so in my my the sensor and display is in working order,but man....as soon as I push the run button,4 dashes appears on the display. I have now done everything except changing the magnet holder to plastic. If I know for a fact this will be the end of it,I will make one,but I am getting close to pulling my hair out for something that should be simple apparently, but I am doing something wrong and don't know what. I will put some tape around the steel magnet holder and tape the magnet to that to test the plastic theory, but I a realy frustrated at this point.
 
You won't believe me............IT WORKS!!!!!!!!!. I don't know IF any of suggested that I put the supply on its own power sorce and I guess you tried doing that @B2 and @mksj by using a 9V battery then I am sorry if I got wrong or something like that. But I must say that it did not work when I used the battery.

What I am trying to say is that I phoned the guy that gave me the 12v supply and told him my headache and he suggested that I remove the 12v from where I connected it to the same wiring that supplied my vfd and put a plug on and plug it in the wall plug sepperate from everything else and the rest is history.

Thanks guys for helping so much and teaching me a lot. You rock.

Michael.
 
Hi Michael,

Congratulations! I am happy for you. Now you know that the Tach is good.

I have found that if the meter on these things are not getting regularly spaced pulses then the display can show zeros. Noise from the spindel motor might be making lots of noise and these are feeding into the meter. Also, I do not know how the meter display will react if the RPM is greater than the display can measure (i.e. pulses too close together). This might also cause zeros to show up. Again, this could be due to noise from somewhere. The fact that you moved the supply plug in might imply a grounding problem or noise on a ground loop.

Anyway, maybe you can yet figure out why you were getting what you were getting.

Dave
 
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