Speed transducer of SPEED2100(Navman), Marine instrument!!!

[bing2005]

Can anyone please tell me how did the speed transducer of SPEED2100 measure the speed of the boat?
I try to design my own display unit for this speed tranduscer. However, i dont know the operation of the speed transducer, such as how i calculate and measure the speed through the paddle wheel of the transducer. When the paddle wheel is moving, how i going to know the speed of the boat?
If anyone know, please tell me.
Thanks a lot!!!

[nevd]

Most of the recent Navman products have a calibration capacity. You would then mount the transducer and run the boat and compare the Navman speed with a known speed eg GPS and calibrate the Navman to be the same.

If you need high accuracy, you will need to do in 2 directions and do the calibration at your intended speed as there will be errors outside the calibrated speed.

Hope this helps.

nevd

[bing2005]

So far i try to measure the output voltage from the speed pin of the speed transducer. I found that when the paddle wheel stop moving, the value will be +0.05V. But, sometimes the value became +11.36V. I dont know why this happened.
Besides, anyone know the correct way to measure the speed of the transducer? Can the speed measure through the output voltage? If can, then how?
Hope someone can help me.
Thanks a lot!!!!

[nevd]

As advised in another forum by Richard, speed is measured by counting pulses and not voltage generated.

nevd

[bing2005]

If used the magnetic field, then how to measure the speed in pulse/time?

[Joe Altman]

A speed transducer is a hall efect sensor reading proximity to the toothed wheel (under water). The output is almost sinusoidal pulse varying from 12VDC to close to Zero Volts. This is why you see different voltages when the boat is not in motion. It depends where the wheel is stationed in respect to the hall efect sensor.

Typically a transducer provides 20,000 to 22,000 counts per NM. You should be able to tune to optimal percision of reading on all recent readouts, NAVMAN, StANDARD HORIZON, RAYMARINE ect....

The only way to check and calibrate it perfectly is by using a osciloscope. Expensive option but it is the only true measure. You can also use a digital counter but it will only tell you the rate of pulse.

Good luck.