RPM help?

[bruce]

I'm having brain fade and can't figure something out. I have an inductive pickup for my speed sensor on my dyno this sensor is triggered by a gear with 30 teeth on it, my question is how do I figureout my frequency so I can figureout how to program my Maxjr digital tach?

Figured I'd ask the forum before heading off to Dynapar for help, its in thier manual but for some reason I am just to stupid to get what they are talking about . . . yes I'm finally getting this dyno project running!

Thanks in advance

[Scott]

30 pulses per revolution or divide the number of counts per minute by 30

[bruce]

I have gotten ZERO help from Dynapar on this problem so I am seeking help from the "collective minds" here on what I am doing wrong in getting this meter to read my rpm's correctly. I'm drawing a blank . . .

I have a gear attached to my dyno shaft with 30 teeth on it and I want my meter to read the rpm's of the shaft, what do I need to input into my meter for the "cal factor"? My sensor is a magnetic pickup. I have attached a copy of the manual in PDF form.



Any help anyone can offer is greatly appreciated., thanks in advance

[Mouse]

Bruce,

I will look at the manual when I get a chance to download it, if nobody else figures it out.

But would having a Tach input on the FP1 be a good thing?

John

[bruce]

[Rick360]

bruce,
I think the cal factor for your application would be 2.


The default is 1 for Hz or pulse per second, it directly reads the frequency of the input.

You want rpm with 30 pulses per rev.

The input measures Hz and calculates what you want to display.

for 1 pulse per rev you Hz x 60 = rpm (pgm cal = 60)

for 30 pulse per rev Hz x 60/30 = rpm (pgm cal =60/30 =2)

The manual is a bit confusing about where you enter that, but I think it is in pgm cal on the programming tree where the factory default is 1.000. Enter 1.000 into that. I think the pgm cal d.p. sets the decimal pt. position for your pgm cal number and should be 0.0000 like the factory default.

Hope this helps.

Rick

[Mouse]

If you are reading zero crossings, you may be getting 2 per tooth, so that would be 60 counts per revolution. Some inductors generate an AC wave form, creating 2 zero crossings per tooth.

[bruce]

Ok now I got that "warm-fuzz" feeling. I also calculated out a factor of 2 and that is what I have programed in. I setup the Sunnen engine analyzer I purchased and used the tach feature on it to get a good idea my tach was close to being right with the 2 factor. The 2 tachs were not readings exactly the same (suspect the Sunnen setup). I have a pretty good air gap on the mag pickup (being cautious) so I can now adjust it to the .005" spec they call for.

The % of output drop is greater with a wider airgap (like I really understand all of that) I do get what they are saying though.

Thanks for the replies!

[Scott]

Bruce, what are you using for a inductive pick up? Brand etc.?

Thanks

RRBD

[bruce]

My pickup is a Red Lion Controls MP62TA00 I have all the info on that sensor. My sensor is actually an OEM unit that has/had 14' of cable. I was in contact with Red Lion when I was first starting my design a few years back.