I am trying to reduce noise in a single-channel recording experiment. I currently have 1 pA noise. I am thinking to use a heavier gauge wire to connect the ground bus (a copper bar) in the air table to the signal ground at the back of the amplifier to reduce the noise, but am not sure how much the gauge should be.
Hi,
In my experience, the connection between the ground bus to the signal ground on the back of the amplifier doesn't make a significant contribution to the noise in a patch clamp setup. That said, I have always selected a wire with a large cross-sectional area (low resistance) to make the connection, because intuitively it makes sense. Use a multi-strand copper wire with a diameter (of the copper wire core, not the outside diameter with the insulation) of around 1.5 to 2 mm. This is equivalent to American wire gauge (AWG) in the range of 15 to 12 (0.0571 to 0.0808 inches in diameter).
But I go back to my original statement - I think you will find that the noise will be reduced by other contributors in the system. The first step is to make sure that there are no 'ground loops' in your grounding. Given that you have described how you have a grounding bus, then this is probably not a problem. The most likely causes for introducing noise are those items that are close to the point of recording:
Hope this helps solve your problems. Good luck!
Hi,
In my experience, the connection between the ground bus to the signal ground on the back of the amplifier doesn't make a significant contribution to the noise in a patch clamp setup. That said, I have always selected a wire with a large cross-sectional area (low resistance) to make the connection, because intuitively it makes sense. Use a multi-strand copper wire with a diameter (of the copper wire core, not the outside diameter with the insulation) of around 1.5 to 2 mm. This is equivalent to American wire gauge (AWG) in the range of 15 to 12 (0.0571 to 0.0808 inches in diameter).
But I go back to my original statement - I think you will find that the noise will be reduced by other contributors in the system. The first step is to make sure that there are no 'ground loops' in your grounding. Given that you have described how you have a grounding bus, then this is probably not a problem. The most likely causes for introducing noise are those items that are close to the point of recording:
Hope this helps solve your problems. Good luck!
Hello Jonas, thanks for your message. We solved the problem. I am filtering at 2 kHz and acquiring at 100 kHz (which I know is too much). Since the signal is only 1 pA we need noise level to be < 0.3 pA. With some concerted effort, we have now achieved around 0.2 pA.
Hello Trevor, thanks for your detailed message. We have solved the problem. Yes, I was told that the cable at the back doesn't matter that much, but it's good to know the gauge for future estimates. Your list is definitely great and I will make sure to check it again when I have noise problems.
Mimi
We have
- made sure all grounds are well connected electrically
- polished the connections between the cooper bar (holes in it, using screws) and the wires with sand paper, because both of them were too rusty. also the outside of the cooper bar was polished.
- ensured that the three panes of the Faraday cages (I have two) are electrically connected and thus grounded
- removed grounds that did not help reduce noise (test one by one)
- let wires loose instead of coiling them in a bundle
- move the power strip further from the amplifier
- cleaned the holder by sonication, used the shortest possible silver wire at the holder and a holder with a shorter-barrel, and use a minimal amount of internal solution bathing the silver wire. Silver wire should be well-chlorided.
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