Help me understand my ammeter

[Chief_Wiggum]

Hi all,

I worked yesterday setting up a mini anodizing tank. The powersupply was a cheapo ATX computer power supply.

I wanted to read the current draw to monitor the anodizing process so I hooked up the DMM's positive lead to the +12V wire of the ps. Then I connected the DMM's ground to the anode in the tank.

Switch everything on and the DMM reads 0 current. Nothing happens in the tank either. Remove the DMM from the circuit and switch the ps on and the anodizing starts.

What the heck is going on? /ubbthreads/images/graemlins/help.gif /ubbthreads/images/graemlins/confused.gif

I'm pretty sure I know how to use my meter, but now I'm not so sure... /ubbthreads/images/graemlins/blush.gif

 

[jayflash]

Assuming the DMM is not faulty, it may have a blown fuse in the current circuit. If this is a decent meter it has a separate jack for current and should be marked for the maximum amperage that is safe to measure. I'm assuming you are using the positive lead in that jack and the meter is set for DC current and not AC.

I apologize if I'm explaining what you may already know, but I don't know what you know...you know?

 

[Chief_Wiggum]

I know /ubbthreads/images/graemlins/grin.gif

It's just a cheapie RS. No seperate terminal for measuring current. Meter was setup for DC current.

I think you're onto something with the fuse though. Never would've thought of that myself /ubbthreads/images/graemlins/ohgeez.gif

edited to add: I'm a moron. The meter is clearly marked 400ma. /ubbthreads/images/graemlins/wink.gif I'm sure the anodizing circuit is drawing more than that. Thanks for pointing me in the correct direction!

 

[jayflash]

Chief, your meter may not have a fuse. If that is the case then look for a loose or burned resistor or current shunt wire. RS and other meters with a 10 amp range go on sale for as little as $15 and less. Spend about $50 and you can get an auto-ranging meter that is more convenient to use. Or get a Fluke if you use the meter often. Good luck on your project.

BTW are you plating old cadmium m*g bulb holders for a pico LED mod? Looks like that's going to be a winner.

 

[Chief_Wiggum]

Thanks, jayflash. I'm going to have to pick up a decent meter one of these days. Ironically, my $3 Harbour Freight meter has a 10A terminal. So I suppose I'll use it for the time being.

I'm just trying to get a 15qt anodizing tank going to anodize some homebuilt lights I've made. I can't seem to find a shop that'll do very small orders for a resonable price.

 

[EvilLithiumMan]

Chief_Wiggum,

I recently purchased Radio Shack's 29 function DMM.
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F011%5F008%5F002%5F000&product%5Fid=22%2D813
It has both a fused 400ma jack and an unfused 10A jack. I've compared a number of voltage and current readings on this meter with my Fluke 177 and they are virtually identical.

By the way, if you get your home anodizing system working, I for one would be very interested to hear all the details!
(What hardware is required. Power needed. Chemicals; their availability and safe handling procedures). And 'beamshots' - we'll need pics. By the way, I live in an apartment and cannot afford any more visits from the authorities regarding strange odors. I hope the anodizing process is 'clean burning', so to speak.

 

[Chief_Wiggum]

Thanks for the link, I'll have to check that one out. Sounds like a pretty good meter for the price.

I also live in a small apartment, so let me give you the scoop so far.

- You can do it at home.
- I'm *very* uncomfortable doing it at home
- The acid, although pretty diluted, is still quite strong
- I bought the acid in quart containers from Autozone. Cost about $5.99/each
- Using a 15 quart rubbermaid tub as a tank
- 10A battery charger as a power supply since I killed the cheapo computer power supply.
- I did successfully anodize 1 small bezel, but couldn't dye it. I'm going to revise the process and try again.
- Watch the homemade forum for an update to "Penlux" for finished pics
- You really need an open area or a very well ventilated one. The acid fumes are strong. I believe the gas given off during the process is hydrogen so be very careful around flame
- You don't want a bunch of acid sitting around after you're done, so you need to neutralize it with a baking sode/distilled water mix, then you can get rid of it. Or you can take it to a battery recycle center I think.
- Goggles, gloves, and probably some sort of gas mask is a smart move

 

[EvilLithiumMan]

Chief_Wiggum,

I'll keep my eyes peeled on the "Penlux" thread. Is it muriatic acid? I remember decades ago my dad using that to clean engine parts.

So, how did you come to learn this process? It's your profession? A terrorist camp in Afghanistan? 'Martha Stewart Living'?

 

[Chief_Wiggum]

There's some good websites around. Try:

http://www.concealcarry.org/ar15/bs-cleanup.htm

http://www.focuser.com/atm/anodize/anodize99.html

http://www.hobbyplating.com/Anodizing.htm

http://www.warpig.com/paintball/technical/anodize.shtml

 

[EvilLithiumMan]

Thank you for the great links - I am immersing myself now !