Hacking a analog multimeter. Soldering the selector permanent.

[Ed.Kloonk]

I've got a Jaycar Multi analog cheapy meter that has crapped out. Wanting to remove the selector knob and wiper and hard wire the board in it's 250VAC range mode and then drill the side and solder in a power cord and mount to the wall for permanent mains monitoring.

There are three tracks which must be shorted.

Would like to know if you have any thoughts about how to solder said tracks.

[codeboy2k]

Seriously?  Just jumper them with a short wire soldered onto the track

[Ed.Kloonk]

Seriously?  Just jumper them with a short wire soldered onto the track

 

Just thought I'd run it past you lot in case there was something dumb I overlooked. Costs me nothing to ask.

[SeanB]

Just be careful that the resistors on the incoming voltage divider may not really be rated for permanent connection to mains, they might be limited by either voltage or power. Fine for a few seconds of connection to mains, but long term it may be problematic, they likely will go open circuit.

As to making it fixed range, go ahead, just remove all the metal parts of the selector and make sure the jumpers will not catch if the knob is turned. As well mark the meter as fixed range.

[Ed.Kloonk]

Just be careful that the resistors on the incoming voltage divider may not really be rated for permanent connection to mains, they might be limited by either voltage or power. Fine for a few seconds of connection to mains, but long term it may be problematic, they likely will go open circuit.

As to making it fixed range, go ahead, just remove all the metal parts of the selector and make sure the jumpers will not catch if the knob is turned. As well mark the meter as fixed range.

Good to know.

Got a feeling that's what is wrong already because meter is playing dead. Was going to duct tape/gaffer tape over the lower half of the meter and write on it 0-250VAC. Meter has a LED continuity indicator and I thought I'd make that light up when power is on.

[SeanB]

You probably will find they used 0.125W resistors inside, which are not exactly rated for use over 100V. You will need to use a pair of equal value ( or within 20%) 0.5W resistors in series for it to be safe for mains use.

[Ed.Kloonk]

You probably will find they used 0.125W resistors inside, which are not exactly rated for use over 100V. You will need to use a pair of equal value ( or within 20%) 0.5W resistors in series for it to be safe for mains use.

Thanks.

And happy 10k posts btw.

[SeanB]

You probably will find they used 0.125W resistors inside, which are not exactly rated for use over 100V. You will need to use a pair of equal value ( or within 20%) 0.5W resistors in series for it to be safe for mains use.

Thanks.

And happy 10k posts btw.

been there before......

I need to get a life.......

[Ed.Kloonk]

 

[Muttley Snickers]

Jaycar have a lifetime guarantee on that meter, if it was mine that was playing up I would take it back and get a working one. I blew up one of their cheap digital meters when I hooked it up to the primary and then put 240 volt on the 12 volt secondary of a transformer, mixed up the colors of the in and out.

Anyway, they took it back and gave me a new one to destroy.


Muttley