Datamarine depth sounder

[bottomscraper]

I believe the watt rating is for the very short time the transducer is sending, most of the time the transducer is listening for the return signal. If the transmitted pulse is too long the depth sounder wouldn't work well in shallow water since the returned echo would start coming back before the transmit pulse was done. A long pulse would hinder a fish finder from distinguishing between multiple fish at different depths. (Sort of like people who spend all the time talking and not listening.)

Anyway the power for the transducer is delivered over some rather small wires and is all supplied from the instrument or black box (at least on the units we use on our boats). The small chart plotter / depth sounders from Garmin only draw about 3 amps. I'm sure others aren't much different.

[Dick Villamil]

I also had problems with my Datamarine depth sounder. I sent it to the forementioned company (after calling to make sure they were an official business). The unit was returned for a nominal charge and has worked flawlessly for the past 10 years. I heard that the former workers (techs) of the Datamarine company formed this company to service old Datamarine units - they did great work!

[Carl Thunberg]

Okay, I got to the bottom of this. I called the manufacturer. I guess they get so many calls about this that they're re-writing their manual to be more clear. It is exactly as Rich described. The watt rating is also a maximum that will practically never be reached. It's what they test their equipment to. Thank you, Rich. Electronics are not my area of expertise.

[Neil Gordon]

If the transmitted pulse is too long the depth sounder wouldn't work well in shallow water since the returned echo would start coming back before the transmit pulse was done.

Not to mention the time between transmitted pulses. If too tightly spaced, the sounder wouldn't know which returned echo was coming back.

[Astronomertoo]

Related to this topic, does anyone know the power requirements of the Datamarine transducer? I recently purchased a Garmin transducer manufactured by Airmar Technologies that uses 600 watts. That seems like a lot of power consumption to me. I haven't installed it yet, and could return it.

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The 600 watts you quoted would be the power of the output pulse, not the device current load, and would be referenced to the frequency of the transmitter output, which is likely between 50 khz and 200 khz. Very likely you do not use more than an amp or 2 of current, so your normal 5 amp fuse or breaker is adequate for protection. You should still verify that. That output pulse is actually a burst of the output frequency, and technically there would be a given number of cycles of that frequency in the transmit "envelope." The circuit works by timing the delay from transmit, to return of the same signal, for which the internal receiver listens for the return first bounce, which is used by the internal circuit to tell you how far the object or bottom is away, given the speed of sound in water. That is the basics of any sounder or sonar, with more discrimination, bells and whistles for more money.
Bob C

[Neil Gordon]

That is the basics of any sounder ...

Except for the no-batteries-required kind, where you simply note how much of the lead line got wet.