How to test GB circuit on work bench

[CAS]

I know you can test EF canceling by waving a magnet near coil but is there any way I can test the effectiveness of GB circuitry on the workbench?

[holyuser]

Just fill 1.5 - 2 kilos of soil in a plastic bag and wrap tightly with tape.

[CAS]

I had thought of that but wondered if there was a more scientific method where you could simulate different ground types with out having to have 1/2 dozen bags of dirt laying around the shop.

[Qiaozhi]

You can use a ferrite core attached to the end of some wood dowelling. Fisher describe this as a ferrite wand in the 1266 service manual.
To test for different ground types, you probably need to do as holyuser said, and get some real samples.

[6666]

A piece of single side 1 oz pcb 125x125mm apparently will sim hot gold field dirt.
A red house brick will sim ground to.
I believe the magnet should be a ceramic type.

[Davor]

Some ferrites are said to have viscous properties, but not all. Ferrites are nice for balancing a VLF, but not for PI. I'm also not convinced about PCB - makes no sense at all.
You'd need some maghemite to do it properly. Aziz literally barbecued some ferrous oxide into maghemite. You may also use old Fe cassette tapes, but make sure no screws or metal screens are there, just tape. If you go for barbecue route, the ferrous oxide is found in perfectly fine grain in pottery hobby shops as a colouring additive for clay. The ferrous oxide on its own has no viscosity, so you have to barbecue.

[greylourie]

Maybe the 125x125 ss pcb material simply shows the level of response a typical P.I would have to some very bad ground. I remember it being mentioned somewhere, but am a bit vague as to context.

[CAS]

I have plenty of old cassette tapes here in the workshop so I can try that. I am going up to the Bendigo gold fields over Easter and can see my self returning with a few buckets of dirt.

[mickstv]

I have plenty of old cassette tapes here in the workshop so I can try that. I am going up to the Bendigo gold fields over Easter and can see my self returning with a few buckets of dirt.

Forget the cassette tape idea. Just go to the whipstick forrest and take a strong magnet with you. Drag the magnet on the ground, if it picks up heaps of small rocks etc, get you your shovel and start digging.

[CAS]

Yeah I was just hoping to try some ideas before I went to the fields so I can take my experiments up with me.

[mickstv]

Yeah just get some old red house bricks and wave them over the detector, any that give a response use for testing your ground balance circuit. The response from a brick is only small but if you can cancel it out, you'll have a chance out in the field.

[6666]

So Cas did you get to the Bendigo gold fields to try out your experiment ?

[CAS]

Going over Easter. Tried with red bricks and was still able to detect small sq of Al under them. I want to get as many variations of timings programmed before I go to Bendigo so I can compare them all.

[6666]

Sorry missed the previous part about going at Easter.

[CAS]

If I had my way I would be there every weekend.