Coil Cable Problem

[Daves]

Hello,
I don't know the exact effect of the coil cable, but I have a problem like this. I produce coils with 2 different cables using the same coil.
Coil 1: When I touch its cable, the detector receives interference
Coil 2: The detector is very stable, I shake its cable, there is no problem.

What does the cable affect?
What should I check?
Is there a place I need to update according to the cable (on the tx or rx side or in the transmit circuit...)
Which values of the cable should I measure?

[Carl-NC]

Poor shielding I suppose. Would help is you tell us what cables were used.

[Daves]

Poor shielding I suppose. Would help is you tell us what cables were used.

I will take a picture of the cable and share it.

[Daves]

Poor shielding I suppose. Would help is you tell us what cables were used.

Carl, cable attached
Note: There is a small pcb inside the coil. The main pcb is inside the main unit.

[Daves]

Poor shielding I suppose. Would help is you tell us what cables were used.

Carl, did you look at the picture?

some useful information for you;

normal coil values calculated direct on coil cables via lcr meter (lcr meter working at 10khz)

RX; 0.19mm wire
Rp: 3.7929 Kohm
X: 390.90 ohm
Lp: 6.420 mH
Q: 9.404

TX; 0.50mm wire
Rp: 678.1 ohm
X: 38.742 ohm
Lp: 618.1ohm
Q: 17.570 uH


when I measured from the coil cable; (the cable is not directly connected to the coil, there is a small pcb in between, if you remember I wrote it.)
1: p 2:tx- 3:tx+ 4:n 5: power

1-2: 22k
1-3: 22k
1-4: 146k
1-5: 22k

2-3: 300ohm
2-4: 40k
2-5: 8ohm

3-4: 21k
3-5: 8ohm

4-5: 34k

[Carl-NC]

Is this the cable that has the noise problem? Is the other cable (the quiet one) a completely different type? Or is it a different piece off the same spool?
Just looking at the photo, the shielding on the TX wires looks pretty feeble. It could be capacitive coupling through your hand to the RX wires.

[Daves]

Is this the cable that has the noise problem? Is the other cable (the quiet one) a completely different type? Or is it a different piece off the same spool?
Just looking at the photo, the shielding on the TX wires looks pretty feeble. It could be capacitive coupling through your hand to the RX wires.

Yes, this is a noisy cable. The only thing I forgot to mention in this cable is that 5, 6, 7 are covered with a thin aluminum film. It is not like a braided shield, but like foil.

The other cable is completely different, it does not have any aluminum shield. There is cotton in the cable. There are copper wires around 1 cable, they may have used it as a shield in the cable. In the original connection diagram, the relevant company connects the tx there.


So, is there anything I can add to the rx front end to fix the noisy cable?

In the original connection of the cable that is not noisy, there is no shield etc. on the rx cables, there are only thick copper wires around the tx cable. So I think there is a shield for the tx, only made of copper. I thought the rx cable would be more sensitive and therefore needed a shield, but apparently the opposite is happening.

Is there anything I can try to fix the noisy cable?

[Carl-NC]

It sounds to me like capacitive coupling. Make sure your shield connections are solid. Use a different cable. White's had cable with foil shielding that failed over time so they quit using it. Is you cable brand new? Otherwise, I don't know. These problems can be difficult to nail down.

[Daves]

It sounds to me like capacitive coupling. Make sure your shield connections are solid. Use a different cable. White's had cable with foil shielding that failed over time so they quit using it. Is you cable brand new? Otherwise, I don't know. These problems can be difficult to nail down.

How can I understand if the aluminum shield deteriorates over time? What will be the effect? How can I check if it is intact?

[Carl-NC]

At White's, a bad foil shield would be noisy when moving or flexing the cable. That's the only test I know of since the shield resistance will probably measure good. Personally, I would just avoid foil shielding.

[Daves]

At White's, a bad foil shield would be noisy when moving or flexing the cable. That's the only test I know of since the shield resistance will probably measure good. Personally, I would just avoid foil shielding.

I understand, I will try with a different cable. Finally, if the problem is "capacitive coupling", how can I solve it?

[Carl-NC]

Differential signaling helps, you're already doing that.
Low impedance drive on the RX helps, you're already doing that.
A well-shielded cable helps, which you may not have.