Tachometer signal

[wsr3]

I recently got an old aquameter tachometer off of ebay and am trying to find what sort of signal it needs. It has two power wires and a long shielded signal wire with a phono plug that, I assume, went to the engine. If I power it and put in a DC voltage it starts to move at about .95 volts and is full scale at about 1.54 volts. The back cover is stamped " 2 cycle outboard". I have tried inputing a frequency signal, but don't see anything consistant.
Thanks,
Bill

 

[wsr3]

Re: Tachometer signal

I managed to get the tachometer apart today and I'm still not sure what signal it wants, but found that the meter is 1mA full scale so I think I'll just try to build a circuit to convert my stator pulses to drive the meter.
Bill

 

[Aurel921]

Re: Tachometer signal

Hi,

Actually, I have the same problem as you, I bought an aquameter tachometer for 2 strokes engine without the transmitter and I am trying to figure it out.

Have you solved the problem?

If you find the answer, I would be grateful if you could help me.

Regards

Aurelien

 

[Silvertip]

Re: Tachometer signal

A two cycle outboard does not derive a tach drive signal from the ignition system -- it derives pulses from the stator. The number of PULSES on the tach signal line will be 1/2 the number of POLES on the stator. Therefore a 12 pole stator produces 6 pulses for each engine revolution. At 3000 rpm for example the signal on the tach line would be 18,000 pulses. Pulses are a modified sign wave so for 90 degrees the pulse rises positive. For the next 90 degrees the pulse begins dropping toward zero, then going negative for 90 degrees before turning rising back toward zero for 90 degrees. AC house current is 60 Hz so you can calibrate the gauge using it (with proper isolation of course). 60 Hz = 3600 rpm (60 Hz x 60 seconds = 3600 pulses/minute).

 

[Aurel921]

Re: Tachometer signal

Hi slivertip,

Thank you for your answer,

The problem is that my engine has no stator (as you mean of course) because ignitiion is done with breakers and condenser.

Actually, it is a Evinrude 60hp V4 made in 1963 and the tachometer is the AQUAMETER model 63 (built in the sixties...). The tachometer is usually coming with a transmitter which is connected between the spark plug and the ignition system.

And my problem is that I don't have the transmitter....

As I understand my tachometer works like this: 1 pulse (since it is connected to one of the spark plug) corresponds to 1 RPM but I have no idea what is the purpose of the transmitter, is ti to decrease the high voltage? is it only a fuse?

If something has already been faced to this problem, i would be grateful to be helped...

Thank you

Aurelien

 

[Silvertip]

Re: Tachometer signal

It is a counter which translate the pulses into a steady state signal that is displayed by the meter. Think of it as being the same as a current tach but with some of the electronics external to the tach itself.