Home Forums ROV ROV Technical Discussions TSS440 Noise (Thruster system??) Reply To: TSS440 Noise (Thruster system??)

Reply To: TSS440 Noise (Thruster system??)

Home Forums ROV ROV Technical Discussions TSS440 Noise (Thruster system??) Reply To: TSS440 Noise (Thruster system??)

#36590
Anh
Participant

Hi Saxophone

It’s interesting to know that background compensation fails with thruster’s trims on. What are standard sample voltages when it fails? Are they over 1000uV?

Excessive voltages may indicate that too much noise coming from ROV. I would suspect when you use thrusters there will be higher 3 phases current flowing causing noise. There is a issue called eddy current you maybe consider. You can find more info about eddy current below (copied from manual) and on attached photos.

I’m using a rear mounting 440 system fixed to ROV frame with separation about 1m and yet haven’t got any background comp issue with thrusters on or off and also with or without earth connection to TSS bottles.

6.3.7 ROV Induced Noise

In some ROVs, whose metallic frame is bolted together rather than welded, eddy currents can flow through the frame. When the ROV is stationary, i.e. during a background comp, the magnetic fields produced by these eddy currents are static and can be compensated out. Once the vehicle moves, however, the conductivity (and resistance) between the frame joints changes, which changes the magnitude of the eddy currents, thus a different magnetic field is produced. This changing magnetic field is detected by the 440 search coils and is seen as signal shifts (i.e. the background comp level continuously shifts) by the system, which in turn is seen by the user as ‘ false’ targets.

The ROV frame can be viewed as a shortened turn with a variable resistance.

To reduce the effects of ROV induced noise, the user can:

a. Find and remove the source of the eddy currents.

b. Extend the coils further away from the vehicle frame.

c. Electrically bond all the conductive parts of the frame so that a constant current flows through the frame joints.

eddy_current_noise_3_196.jpg
eddy_current_noise_3_196.jpg

eddy_current_noise_2_140.jpg
eddy_current_noise_2_140.jpg

eddy_current_noise_1_924.jpg
eddy_current_noise_1_924.jpg

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