Building a battery for Tek 222 handheld scope

[iXod]

Duplicating Paul's effort here:



(start at 11:20).

What common insulator would you use? I looked at 1/32 inch (0.79mm) polycarbonate but seems too thick.

Ideas?

Cheers.

[David Hess]

What common insulator would you use? I looked at 1/32 inch (0.79mm) polycarbonate but seems too thick.

https://en.wikipedia.org/wiki/Fishpaper

[Andy Watson]

I just watched this video the other night. The thing that I did NOT notice was modification of the charging circuits to account for the different battery technology. Lead acid - Nickel Metal Hydride ?

[iXod]

I just watched this video the other night. The thing that I did NOT notice was modification of the charging circuits to account for the different battery technology. Lead acid - Nickel Metal Hydride ?

@ 1:01:20

It's trickle-charging using the original circuit. Seems to work well. No issues apparently.

[iXod]

https://en.wikipedia.org/wiki/Fishpaper

Thanks. Looks good. I've ordered some.

Cheers.

[David Hess]

https://en.wikipedia.org/wiki/Fishpaper

Thanks. Looks good. I've ordered some.

Cheers.

Fishpaper behaves like thick business card stock but is much tougher, stiffer, and heat resistant.  I usually see it used to direct air flow around or insulate line side and high voltage circuits but its mechanical properties make it good as a general purpose insulator.  I have also seen it used to insulate batteries.

[iXod]

Fishpaper behaves like thick business card stock but is much tougher, stiffer, and heat resistant.  I usually see it used to direct air flow around or insulate line side and high voltage circuits but its mechanical properties make it good as a general purpose insulator.  I have also seen it used to insulate batteries.

I guess FP gets its name from the scale-y look, kinda like fish scales? Just discovered that some fuses (ie, HRC type?) bodies are made from this stuff.

iX

[David Hess]

I guess FP gets its name from the scale-y look, kinda like fish scales? Just discovered that some fuses (ie, HRC type?) bodies are made from this stuff.

That has always been my assumption but I do not know.

I have also seen fuses which apparently use it for their body and I have seen fishpaper covers for fuse blocks which would otherwise be exposed inside of an instrument.

[trukresom]

Another solution to solve the battery problem for the Tek222 is to mill the inside of the case at some
points to make room for an available 8V battery. So the charging circuit can be left as it is.
At least this approach worked for me.

[Fungus]

I guess FP gets its name from the scale-y look, kinda like fish scales? Just discovered that some fuses (ie, HRC type?) bodies are made from this stuff.

I always assumed it's there to make the body slightly flexible - so it doesn't shatter when the metal vaporizes.

They're way overpriced though. It's not a precision device, it's a piece of wire in a tube full of sand. I can buy stuff for $0.10 that's more expensive to manufacture than that.

(hell, I can buy three complete multimeters for the price of one of those fuses - with LCDs, PCBs, chips, probes...how can they be cheaper to manufacture than a fuse?)

They charge what they like because, well... you wouldn't want to be "unsafe" would you? 

[David Hess]

I guess FP gets its name from the scale-y look, kinda like fish scales? Just discovered that some fuses (ie, HRC type?) bodies are made from this stuff.

I always assumed it's there to make the body slightly flexible - so it doesn't shatter when the metal vaporizes.

They're way overpriced though. It's not a precision device, it's a piece of wire in a tube full of sand. I can buy stuff for $0.10 that's more expensive to manufacture than that.

(hell, I can buy three complete multimeters for the price of one of those fuses - with LCDs, PCBs, chips, probes...how can they be cheaper to manufacture than a fuse?)

They charge what they like because, well... you wouldn't want to be "unsafe" would you? 

There is another discussion going on about these fuses.  They fill a real need by being able to safely interrupt high DC voltages but I have no idea why they are so expensive.