Warning, Distilled Water for ND:YAG

[mixedgas]

After testing several "grocery store" brands of distilled water, ALL of them had high conductivity. All were no better then TAP water.

If you have a wet lamp YAG laser, when using distilled water, ensure that the laser's De-Ionizer filter has time to clean up the recently added water.

RIP one QCW20 Lamp.....

Steve

[danielbriggs]

Here here!
I lost an ALE years back to the same thing.

That was Tesco / "Walmart" DI water.

Now I only buy proper spec'd DI water from a local chemical supplier as it comes with a test certificate from each batch.
No problems since.

[daction]

Heya has any used r o water?

[Photonbeam]

Distilled water is not necessarily DI water (deionized). I used grocery store distilled water but circulated it through the system's DI cart until the conductivity was low enough (resistivity was high enough) before igniting the lamp. The manual says the water's resistivity must be greater than 500K ohms and be free of contaminants.

[turbohead]

What is the best way to test the resistivity?

[mixedgas]

What is the best way to test the resistivity?

Search : resistivity tester water... Conductivity tester water...

Then get some fresh resin from a aquarium place and make a master sample to check it.
Just setting in a bottle, the water will pick up ions, so always best to make a master batch.


Its possible to buy a sensor module that plumbs into the cooling loop. I'll look at that shortly.

Steve

[dsli_jon]

After testing several "grocery store" brands of distilled water, ...

Good tip for the kiddies, Steve, but, I always kinda thought that was, umm, 'elemental'.. Ya know, like... 'Always pillage, BEFORE you burn'.. ALWAYS test before you fill 'er up.. I'll usually take a DMM with me, and test right outside the store.. if it's not over 1000kΩ, I dump it and go buy more... and, hey! At $1.29 - 1.59 / Gal + bloody water-Tax (!) why not!!

...I do-find, however, that 'drug store' / pharmacy distilled usually seems to be a 'safer-bet', than grocery-store distilled.. Not necessarily because it's a 'better brand', etc, but just because (..in-theory, here..) you've got more people with 'more reasons to buy distilled' in a drug-store (irons, vaporizers, nebulizers, CPAPs (?) baby-formula mixes / medicine-mixes, health-drink powder mixes, etc, and/or other medical-based reasons, etc..) than in a grocery store, so, likely, there is 'higher-turnover of the stock-available', and therefore, you're less-likely to get dist-water that's been 'sitting' for 6+ months, etc.. ..That's just my 2-bit observation, anyway..

..But, yes, in any-case, definitely run it a good-bit thru your (actual..) DI-filter (which, you should always-change upon acquisition of a 'new' machine..) before ya try and light that puppy.. Though, they are supposed to *not* strike if the water is too-conductive, so.. If yer ALE strikes, and blows a lamp / the ALE, well.. that's a bad-ALE or ground-strap, regardless of the water..

Dos pence...
j

[buffo]

if it's not over 1000MΩ, I dump it and go buy more..

Given my background in high-purity water systems, I'm going to nit-pick here. (Sorry - I can't help it!)

The maximum resistivity for water is 18.3 meg-ohm. One thousand Meg-ohm is physically impossible for water.

ASTM Type I water is defined as greater than 10 meg-ohm. ASTM Type II is 1 meg-ohm or better, and this is all you really need for a 'scope.

Another important note: highly de-ionized water is fiercely aggressive and will pull ions into solution from just about any material, including stainless steel and most plastics, not to mention air! So in order to maintain water at 10 meg-ohm or higher you need to continuously recirculate it through a DI resin bed. If left standing in an open beaker, ASTM Type I water will quickly degrade (in ~ 15 minutes) to ASTM Type II specs, if not lower.

And yes, no matter what you use for your DI water source, you really should run the recirc pump for a while to move the water through the DI cartridges to be sure it's all cleaned up before you fire the PSU. (And as you said, make sure the cartridges are new!)

Adam

[daction]

Best plumbing lesson ever.

[tribble]

Question from ignorance... if DI water is so aggressive/corrosive, why is it used in sensitive electronic/optical equipment? Is there no other/better cooling solution?