Testing a Depth Transducer

[ShaunG]

My depth has just stopped working on a tacktick system. The transducer is an airmar and was originally installed on a Raymarine system. The depth was working fine until today, the display now reads just dashes.

I have plugged a new transducer in and suspended it in the water and the reading works fine ( wiring and instruments are ok), although it also reads as dashes when not in the water

The exisiting transducer is mounted through the hull, with the head flush with the bottom of the hull. I have looked at the FAQ 's on the airmar website but before i email them i thought i would ask if there is a way to test the transducer with a multimeter, the resistance and the voltages are the same on the new transducer and the old.

I guess it may be that the transducer head is coated in weed and slime, has anyone experianced this.

I can replace the transducer when the boat comes out of the water, however i would like to avoid this as the mounting hole sizes are different, I would like to establish if the fault is due to fouling or a faulty transducer before the boat is lifted.

Many Thanks

 

[lydiamight]

I seem to remember that a portable radio radio tuned to nothing in particular on the long wave band should emit a series of clicks as it picks up the pulses from the transducer. I think that you have to have the radio reasonably close to the transducer

 

[Stemar]

I can't help with testing the old transducer, but you may not need to wait for a lift to fit the new one. Assuming you have a solid GRP hull, get a dob of blutack, attach it to the bottom of the transducer and press it against the bottom of the hull in convenient places. The chances are that you'll find a place where it works fine. Mine is fixed into the corner of a locker with few a good dollops of Gosport pound shop's equivalent of No More Nails and has been in situe for 3 years now.

 

[ShaunG]

Thanks for the suggestion of the radio, I have a LW radio receiver and i am sure that most transducer's are 200khz ( can anyone confirm) if this is the case i should be able to use a long wire aerial around/near the transducer and tune to 200 khz and hear the clicking.

SOunds like a great idea, has anyone else tried it?

 

[doca]

I fitted an in-hull tacktick depth sounder and it works very well - I really did'nt want any more holes in the hull. I got the dashes instead of a reading at one stage and after checking all connections, plus a direct "in the water" testing of the transducer which gave a reading, I discovered finally that the amount of oil in the transducer housing was insufficient. I topped up the oil and its on the button ever since.

 

[jwrhind]

Don't know if you'll "hear" the depth transducer on the radio, but sometimes it's possible to 'feel' the "clicks" with your ear next to it.

Have you checked the wiring all the way to the existing transducer?

Airmar make retractable depth transducers. I know that they seldom fail, but it may be worth fitting a retractable one, especially considering the cost of a lift out.

R.

 

[Billjratt]

Yup, you get the e/s pulses near the old light programme on longwave if it's (the sounder) working. Remember, the transducer is a crystal and is part of the pulse circuit (that's why they don't like you to cut the cable). If there's a fault in the tranducer or the cable it won't pulse (tick on the radio) Also you won't get much sense out of measuring the resistance of the transducer.

 

[Mrnotming]

Mine is on a good thick bed of plasticine kids modelling stuff. Works well!

 

[Mrnotming]

Sorry, should have added that this is internal, to a GRP single skin area of the hull

 

[oldsaltoz]

If the radio confirms the sounder is clicking there is a good chance it has a bubble of air under it and remounting should solve the problem.

You can test new locations by dropping it into a plastic bag and cover it with water, wet the area between the bilge and bag to eliminate any air to find a new location.

Any air (even in the fibreglass layup) will prevent a signal.

Avagoodweekend.......

 

[simonfraser]

my tacktik depth is stuck on the inside of a ply/epoxy hull with silicone, works fine
leave the old one where it is

 

[William_H]

I can confirm that a sounder transducer has a very high resistance ceramic type transducer ie a piezo crystal that deflects with voltage. You will not measure any conductivity with a multimeter so you can not test the wiring etc.
If the transducer is faulty it is most likely wiring connections to the piezo crystal. Before you throw it away you may be able to tear it apart to expose the wiring. If you can find the break you may be able to fix it. (But you will probably have to buy a new one) olewill

 

[JKay]

Fire it up and "clasp it gently"if it clicks in your palm it works

/forums/images/graemlins/blush.gif

cheers Joe

no lube!!!