echo sounder question

[mldpt]

Has anybody managed to run two echo sounder displays from one transducer. if so do you connect them in Parallel or series, alternative would be to use two transducers. I dont want to use one display as a repeater.
Mike

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[Guest]

Cable length is critical

You cannot series them - as the cable length determines the time frame count to deternine the depth along with time to return signal through water.
You cannot parrellel - how do you connect the cable without cutting / introducing a splice etc/junction etc. degarding the signal and in terms of a weak deep signal - possibly losing it.

BUT - if your set outputs NMEA or seatalk - then you can use that signal to another that accepts NMEA or Seatalk - OR to a PC charting program that displays depth data as well.


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[fluffc]

Electrically speaking, it is not possible to do this, as the echosounders are constantly using the transducer (either transmitting or listening). To have two echosounders using one transducer is likely to confuse the echosounder or blow up some of the circuitry in the tx/rx circuits...

A way of getting around this would be to have a switch in the system that will select which echosounder is using the transducer. Naturally, this will mean that only one echosounder can be used at a time.

IMHO, an ordinary switch can be used - despite recommendations not to modify cabling; and the cable length being critical blah blah - echosounders work in the ultra sound range of the spectrum which is quite low frequency. Cable length only becomes an issue at higher frequencies. As a proviso, don't alter the length too much as this could cause resistance matching (not impedance matching as the frequencies are so low) problems.

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[john_morris_uk]

The reason the cable length is important is that the designer has used the capacitance of the cable as part of the tuning for the tx/rx circuit. Lots of echo sounders do this. Its messy and not very appealing electronically, but I agree the length certainly doesn't alter the propagation timing of the ultrasound frequencies but it is still critical IMHO. Don't think the resistance is a key issue here either. However it does mean you can have a switch in the cable so long as the length remains more or less the same. Bond all the braids together and switch the central conductor.

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[VicMallows]

Agree totaly. Lazy designers.

Vic

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[chippie]

Electrically speaking, would it be possible to just parallel the display? presumably this would have the desired effect.

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[fluffc]

Not if each display is actively using the transducer. However, if you were to link one "display" to the transducer, and connect the other one to the first via NMEA; that might work. But probably not with your equipment.

The way to have two displays showing the same data and sharing the same transducer is to have a primary echosounder unit (which includes circuitry for the transducer) doing the work (measuring the depth). Then connect a second "slave" display to this using NMEA or whatever proprietry network is needed.

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