Refueler
Well-known member
Make and model of Sounder gear ??
Transducer replacement
- Thread starter tolhurstorganic
- Start date
Make and model of Sounder gear ??
Scubadoo
Well-known member
Garmin Striker vivid 7sv with a GT52HW-TM transducer.
Refueler
Well-known member
Not co-ax then ....
PaulRainbow
Well-known member
You can alter the length of the Garmin cable.
PaulRainbow
Well-known member
See post #14
Ian_Edwards
Well-known member
I think that the correct answers is on this thread, it's just all jumbled up.
There are, in general two types of echosounder:
1) Older models where the transmitter and receiver are in the head, and the transducer is dumb. I this case the cable length could be important. Not because of any timing issue, as already pointed out, the pulse travels at close to the speed of light in the cable, so any ultra small delay in the cable is insignificant. However, the impedance (capatitance, inductance, and resitance) of the cable may be important.
A typical yacht transducer is made of a ceramic, often barium titanate. These are capacitive. If you looked at Bode plot, of resitance on one axis and reactive componeets on the other, for different frequencies, you'd see a circle or elliptical shape, offset to the right. To get a good power transfer, that plot need shifting to the left at the operating frequency, to make the load look restitive, not reactive like a capacitor.
The designer does that by adding external componets. The cable will be part of that mix.
Shortening or lengthening the cable may well change the impedance of the tuning componets. The transducer may still work, if the changes are small, but it is unlikely to work as well as the original. The transmitter and receiver will be working with a reactive load, not the resistive load it was designed for. So, yes, cable length can be important, and yes you can cut it, providing you don't cahange the length or the impedance significantly.
2) More modern sounders have smart transducers with transmitters and receiver built into the transducer. In this case the cable lenght is unimportant. It just has to be good enough to transmit the data stream.
Just for reference, I spent several years in the 1970's designing and build experimental ultrasonic transducers.
There are, in general two types of echosounder:
1) Older models where the transmitter and receiver are in the head, and the transducer is dumb. I this case the cable length could be important. Not because of any timing issue, as already pointed out, the pulse travels at close to the speed of light in the cable, so any ultra small delay in the cable is insignificant. However, the impedance (capatitance, inductance, and resitance) of the cable may be important.
A typical yacht transducer is made of a ceramic, often barium titanate. These are capacitive. If you looked at Bode plot, of resitance on one axis and reactive componeets on the other, for different frequencies, you'd see a circle or elliptical shape, offset to the right. To get a good power transfer, that plot need shifting to the left at the operating frequency, to make the load look restitive, not reactive like a capacitor.
The designer does that by adding external componets. The cable will be part of that mix.
Shortening or lengthening the cable may well change the impedance of the tuning componets. The transducer may still work, if the changes are small, but it is unlikely to work as well as the original. The transmitter and receiver will be working with a reactive load, not the resistive load it was designed for. So, yes, cable length can be important, and yes you can cut it, providing you don't cahange the length or the impedance significantly.
2) More modern sounders have smart transducers with transmitters and receiver built into the transducer. In this case the cable lenght is unimportant. It just has to be good enough to transmit the data stream.
Just for reference, I spent several years in the 1970's designing and build experimental ultrasonic transducers.
Refueler
Well-known member
I'm just thinking this through ... and its only for the co-ax cable type (twisted pair ... NMEA etc is another matter).
OK - we know that electrical current or carrier is fast ... lets say speed of light .. not really interested in discussion about that .. the matter is thats a 'carrier' ...
The data signal that the 'carrier' carries - that is carried at that speed but its data change and information based on that data change is a separate speed matter .. lets say speed of sound ...
Now we see a huge difference in speeds .. the electric carrier vs the data change it carries ...
Just thinking out loud ...
OK - we know that electrical current or carrier is fast ... lets say speed of light .. not really interested in discussion about that .. the matter is thats a 'carrier' ...
The data signal that the 'carrier' carries - that is carried at that speed but its data change and information based on that data change is a separate speed matter .. lets say speed of sound ...
Now we see a huge difference in speeds .. the electric carrier vs the data change it carries ...
Just thinking out loud ...
justanothersailboat
Active member
Thanks Ian_Edwards. I tried to write an answer a bit like that but you know more about it than I do. Lopping a chunk off the cable affects signal travel by irrelevant nanoseconds but makes a substantial difference to its capacitance. The NASA sounder doesn't seem to be terribly sophisticated.
