Ladies & Gents

I have a Navman 3100. Depth worked fine last season bu tshows nothing
now. Is there any way to check the depth sounder cable to determine
whether is was damaged over the winter? A visual inspection of the
accessible parts of the cable has shown nothing unusual.

Many thanks in advance

Matt

wrote in news:61d6b5e4-c19d-4b64-928a-
:

Ladies & Gents

I have a Navman 3100. Depth worked fine last season bu tshows nothing
now. Is there any way to check the depth sounder cable to determine
whether is was damaged over the winter? A visual inspection of the
accessible parts of the cable has shown nothing unusual.

Many thanks in advance

Matt


The transducer of a depth sounder is a piezoelectric crystal. Left open
circuit, it generates a DC voltage which can get quite high if left open
for a day. The large, high powered transducers in a Naval submarine are
always left shorted to prevent this voltage buildup because it can kill
just sitting there on a pallet. Their crystals are huge compared to
yours.

So, if we UNPLUG the transducer from the sonar and leave it open
overnight, we can take a high impedance digital voltmeter and measure the
crystal's DC voltage, briefly as the meter's 10M ohms discharges it like
a little capacitor, IF the cable is:
A - connected to the transducer in the bilge....and....
B - doesn't have any leakage across the conductors which will drain away
this high impedance source's voltage.

Do NOT connect an ohmmeter across the transducer, which always measures
an open anyway, because the transducer's high voltage may damage the
ohmmeter.

You should see some level of DC voltage if the cable and transducer are
in working order. If not, it's 50/50 which is the problem.

Larry,
You have my interest. I see these transducers shipped new in boxes, open
circuit, sitting on shelves. I never saw a high voltage warning label on any
of them. What is the recommended method to test a transducer?
Steve

"Larry" wrote in message
...
wrote in news:61d6b5e4-c19d-4b64-928a-
:

Ladies & Gents

I have a Navman 3100. Depth worked fine last season bu tshows nothing
now. Is there any way to check the depth sounder cable to determine
whether is was damaged over the winter? A visual inspection of the
accessible parts of the cable has shown nothing unusual.

Many thanks in advance

Matt


The transducer of a depth sounder is a piezoelectric crystal. Left open
circuit, it generates a DC voltage which can get quite high if left open
for a day. The large, high powered transducers in a Naval submarine are
always left shorted to prevent this voltage buildup because it can kill
just sitting there on a pallet. Their crystals are huge compared to
yours.

So, if we UNPLUG the transducer from the sonar and leave it open
overnight, we can take a high impedance digital voltmeter and measure the
crystal's DC voltage, briefly as the meter's 10M ohms discharges it like
a little capacitor, IF the cable is:
A - connected to the transducer in the bilge....and....
B - doesn't have any leakage across the conductors which will drain away
this high impedance source's voltage.

Do NOT connect an ohmmeter across the transducer, which always measures
an open anyway, because the transducer's high voltage may damage the
ohmmeter.

You should see some level of DC voltage if the cable and transducer are
in working order. If not, it's 50/50 which is the problem.

"Steve Lusardi" wrote in
:

Larry,
You have my interest. I see these transducers shipped new in boxes,
open circuit, sitting on shelves. I never saw a high voltage warning
label on any of them. What is the recommended method to test a
transducer? Steve



Plug it into a sonar unit, put it in the water and see if you can see the
bottom in a hundred meters of water would be best.....

I was trying to test his transducer and cable out from the easy end to
get to without swimming in bilgewater. If the voltage rises from the
piezoelectric effect of the transducer listening to the noises in the
water, it's probably 99% just fine. If no DC ever shows up, cable or
transducer is bad, not the control head/transmitter/receiver....probably.
He didn't say he had a neighbor to swap units with to test it.

The tiny transducers on pleasure boats don't need a kill warning tag on
them. The transducers in a nuclear sub, to give you a perspective are
each about 20cm in diameter and 1.4 meters long. There are hundreds of
these in an electronically scanned array fore/aft/up/down/beamwise

It's no fun scrunched up in the sonar dome testing the damned things with
the test set, either....no air, hot as hell, cramped tiny space, no place
for your legs and feet. Been there....done that....it sucks.

What's fun is when the old transducers are sitting face down on a pallet
waiting disposal. Take a screwdriver and short them out quickly you get
a real impressive POP!....(c; "Hey! Why did you guys leave these things
ON?!", you ask the newbie who jumped.

The effect is the same as the spark igniter on a new gas grille. You
bang on the transducer, you get a high voltage spike from the
piezoelectric crystal. There's not much current unless the crystal is
huge and the circuit is very high impedance...high voltage.

In article
,
wrote:

Ladies & Gents

I have a Navman 3100. Depth worked fine last season bu tshows nothing
now. Is there any way to check the depth sounder cable to determine
whether is was damaged over the winter? A visual inspection of the
accessible parts of the cable has shown nothing unusual.

Many thanks in advance

Matt

You can check the Transducer with an Ohm Meter and it should show a very
High Impedance across the Transducer Leads, and NO resistance to the
shield from either lead. If that all is OK, then connect it to the
unit, and stick your ear up to the transducer. You should hear a clicking
sound. One click for each transmit pulse. No click, Blown Transducer.
If your water bound, you MAY try sticking your ear up against the inside
of the HULL close as you can to the transducer and listen for the
Clicking. The only other way is to get a Depth Sounder Transducer
Impedance Meter, and do a full out Test of the Transducer. These
devices aren't cheap, but they do a very GOOD job testing Transducers.

--
Bruce in alaska
add path after fast to reply

All depth sounders "tick" a little when they transmit. The sound is audible
with the ear, although very silent. You can also
put your finger on the bottom end of the transducer and "feel" the
transmission. (In case you have a removable depth transducer or
your yacht is on land) This is a rough test and does not really tell if your
transducer is receiving the echoes or if your instrument
is working, but the audible tick and tiny tapping is a precondition for the
transducer to work. Have tested new installs on
maybe 100 different yachts depth transducers this way (all Raymarine or B&G,
both using Airmars transducers) its has proven to
be a very good and easy primary test on yachts on land.

Regs,
TomS


wrote in message
...
Ladies & Gents

I have a Navman 3100. Depth worked fine last season bu tshows nothing
now. Is there any way to check the depth sounder cable to determine
whether is was damaged over the winter? A visual inspection of the
accessible parts of the cable has shown nothing unusual.

Many thanks in advance

Matt

On Jun 11, 3:10*pm, "TomS" wrote:
All depth sounders "tick" a little when they transmit. The sound is audible
with the ear, although very silent. You can also
put your finger on the bottom end of the transducer and "feel" the
transmission. (In case you have a removable depth transducer or
your yacht is on land) This is a rough test and does not really tell if your
transducer is receiving the echoes or if your instrument
is working, but the audible tick and tiny tapping is a precondition for the
transducer to work. Have tested new installs on
maybe 100 different yachts depth transducers this way (all Raymarine or B&G,
both using Airmars transducers) its has proven to
be a very good and easy primary test on yachts on land.

Regs,
TomS

wrote in message

...



Ladies & Gents

I have a Navman 3100. *Depth worked fine last season bu tshows nothing
now. *Is there any way to check the depth sounder cable to determine
whether is was damaged over the winter? *A visual inspection of the
accessible parts of the cable has shown nothing unusual.

Many thanks in advance

Matt- Hide quoted text -

- Show quoted text -

A thank you to everyone who responded. It's appreciated. Tine ti
play this weekend

matt

"Steve Lusardi" wrote in
:

Larry,
You have my interest. I see these transducers shipped new in boxes,
open circuit, sitting on shelves. I never saw a high voltage warning
label on any of them. What is the recommended method to test a
transducer? Steve



I'm sure the manufacturers would rather you just bought a new one. Not
sure what they'd "recommend" to test. Most problems I've ever seen are
caused by the cable rotting off them.

If the transducer is mounted in the hull, there should be enough noise
going by it to make some signal you could see on an oscope and you can
probably see some DC voltage if nothing is leaking....which would be
unusual in a bilge, I'm afraid.

Measure DC volts with an autoranging Digital voltmeter (They're 10M ohms
impedance) and if you get no reading, switch to ohms and hope it reads
infinity (open circuit), which is what the crystals are. Plug in a
scope and see if you see any noise at the crystal frequency, which is
too high to hear, of course. If you know someone else with the same
sonar nearby in the marina, have him fire up his sonar then look at the
oscilloscope on the test transducer to see if you can see his pinging
reflecting off the bottom. If you see nothing, take your sonar head
over and plug it into his transducer to see if your head is working. If
it is, bad transducer...or bad transducer cabling. it's not rocket
science.

Sorry I was late replying. I was sailing up 80W from S Fl bringing
someone's Jeanneau 40DS home with them...(c;