Is this cheap DO meter better than nothing?

[CharlosCarlies]

I know there have been a few threads on this, but thought I'd ask about a particular model that gets at least decent reviews on Amazon. We will only be using the meter for wort aeration, so I'm wondering if less than perfect accuracy is at least better than not measuring at all. Obviously I'd love to be able to spend more, but as always budgets are getting in the way.

http://www.amazon.com/Milwaukee-MW60...words=do+meter

Any other suggestions for <$1000 meters that would at least be better than nothing?

[dick murton]

Personally, I would spend the money on helping to set up a decent flow meter and injection system into the cold wort. If you measure the air (or oxygen) flow rate and pressure differential, you can then calculate the mass of oxygen going in. Of course you need to make sure it is fully dissolved by injecting agains high turbulence and back pressure, but you would have to do that anyway to get consistent oxygen levels.

Don't forget that unless you use oxygen, you won't get much more than about 8ppm oxygen dissolved in the wort anyway - maybe 10 ppm if cold and low gravity.

If you want to control the wort oxygen injection rate using an O2 meter, I think you will need a much more sophisticated meter than this. And if you try and measure the DO2 after the wort run has finished, then the time of sampling, time of yeast pitching and yeast pitch rate will affect how much is left to be measured by the meter.

[CharlosCarlies]

Thanks Dick...seems like solid advice as always.

We will be investing in a good flowmeter, etc. I was planning on doing the calculations to get a good estimate for our first few batches, but was hoping to use a DO meter just to test and adjust as necessary. Good call on timing of sampling the wort (at the very least we need to be consistent). My plan was to use a cross w/ a sample port to pull a sample as we're racking in to the tank, but I'm always open to other ideas.

[TL Services]

This type of meter is designed for measuring oxygen in free-flowing rivers, etc. where there is a high volume of 'sample' with oxygen levels close to saturation and where speed of response isn't critical.

Whilst wort oxygen is also of a similar level at around 10ppm, I wouldn't advise using one of these for controlling something as critical; as DM has already said, better to invest in a good, robust flow/injection system.

Then there are basically two options for wort O2:

Inline: Wall- or panel-mount meter with sensor mounted in the main, ideally at a distance from the O2 injection point to ensure complete dissolution. Most systems have some sort of output, eg. 4-20mA, so can be used to control or fine-tune injection and also to monitor O2 level throughout a run. They can also be used to activate alarms, should the level go outside control limits;

Portable: A good portable meter can, with the right configuration, be used pretty-much across the production process, from wort to final pack. Whilst a portable doesn't necessarily have the control facility, it is a useful tool for spot-checks and has the benefit for many craft operations that by using one meter, this means every DO2 analysis can be traced to that single unit for audit trails, etc.

Good, second-user meters needn't be expensive either.

[PMallory]

TL Services, for the wall or panel-mounted meter with sensor you mentioned, do you have a recommendation for a decent brand?
Also, for the flow/injection system, how do you know if you are providing enough back pressure to keep much of the oxygen dissolved?

[TL Services]

Inline systems include Orbisphere, Mettler & Haffmans (I've sent you a PM with more details).

Very little pressure is needed to maintain the oxygen in dissolved state; cooled wort at not much above atmospheric pressure will maintain around 10ppm dissolved O2 without any issues.