I have run into some problem with stray voltages which causes some measure error for me and as i understand it the only way to get rid of it is to add a ground probe.

I have seen those for sale in the US but never in Sweden so i thought of making my own but I'm interesting in the resistance of the commercial probes, is it close to zero or is it high resistance?

I only had to use like 5Mohm to get rid of my measurement problems.

Is it better to use high or low resistance, does any of this affect the electronic measurements in a better or worse way?

Can i use Stainless steel instead of titanium, it seems hard to get (it's only a planted fresh water tank)?

I think SS is fine instead of Titanum.

It's most likely the ballast from the lighting that's causing the issues.

Regards,
Tom Barr

All of the electronics in the ballast is inside a metal can, which is grounded, so that part shouldn't cause interferrence. But, the wires from the ballast to the bulbs carries high frequency AC current - a great way to generate interferrence. Maybe those wires should be shielded?

Thanx for your answers,

I also think the main starting point of the problem is the ballasts (the emission it self could be from wires or the tubes), I changed the ballasts to dimmable versions and the problem is seen as spikes when it is in "dimming mode", there were small tendencys before i changed the ballasts but not that big of a deal.

If i only use it for on / off then it's like the old ones, small tendencys, i guess the dimming state is not the best state to be in.

But the problem seems fairly easy to get rid of.

I have read that most ground probes seems to be directly connected to ground without a serial resistance, but i think i will go for something in the area of 1Mohm, this seems to get rid of my problem but it will not help me with faulty electrical stuff (but thats not the reason for it).