Dissolved Oxygen Meter

[barneey]

In order to improve my setup I`m going to purchase a 0.5 micron stone to see what the improvement will be over the existing 2 micron one I have.

[jaybie]

Anyone know where I can hire / borrow a dissolved oxygen meter? from.

http://www.waterrauk.com/pages/product/ ... APHRDO.asp

http://www.em-solutions.co.uk/products/ ... monitoring

http://www.stsanalytical.com/equipment-hire


Whether or not any of these companies will charge a sensible amount is anyone's guess, but it'll be a start. Try searching for "water quality hire"

JB

[barneey]

Thanks for those companies, one has already emailed back but am now waiting on prices for a couple of days hire.

[barneey]

So far the response has been

Thank you for your enquiry regarding Equipment hire.
We have DO meters available for hire and the rental is £49 per week.
The meter is handheld, with probe, operating instructions and carrycase. All equipment is QC checked prior to issue.
Cost of carriage (next day delivery) is £20 eachway (ie £40 for delivery and collection).
These prices do not include VAT.
I hope this is satisfactory and await your instruction to proceed.

So a fairly expensive exercise, I make it £49+£40 = £89.00 + VAT = £106.80 for the weeks hire!

[barneey]

Got myself a new 0.5 stainless stone + found a cheap second hand WalkLAB DO meter to try out, so will carry out a few experiments out over the next couple of days.

[barneey]

Carried out a few experiments today with the meter.

1) Long winded way to calibrate the thing, first no probe + screw driver adjustment to zero (easy), second with probe in air (for 30mins!) then screwdriver adj to 20.9ppm.
2) Tested some tap water - left probe submerged in tap water at 19 C for 15mins got a reading of 7ppm
3) Had 20 litres of water left over in a plastic jerrycan (been used to fine tune the plate chiller), tested this again submerged probe for 15mins got a reading of 6.40ppm 21 C.
4) Using the new .5 ss stone attached by a piece of pipe to the oxygen flow meter passed oxygen thru liquid 90 sec at 1 ltr per min. Tested as before with meter afterwards got a reading of 9.80ppm so only a 3.40ppm increase.
5) Thought I would try again using the same water etc, 90 sec blast at 1ltr per min, got a reading of 13.2pp so a further increase of 3.50ppm.

Conculsion for the experiment today 6.90ppm over 180sec at 1ltr per min.

There was quite abit of oxygen reaching the surface of the water and thus wasted.

I would be most gratefull for any suggestions of improvement / observations as to my method used.

Cheers

[gregorach]

At least it's consistent. Factors involved would be water temperature (colder is better) and the depth of water you're bubbling the gas through (deeper is better). You might also get better absorption (as a percentage of gas used) at a lower flow rate.

I'd be really curious as to whether this meter would work with wort...

[barneey]

Cheers Dunc for the reply....

For todays experiment:- I used 20 litres of water, boiled yesterday afternoon, splashed into jerrycan and left to cool over night, temp today 24 c (3c more than yesterday).

I reduced the flow rate to approx 0.5 litres per min on the oxygen side of things.

1) Inital level 3.4ppm
2) 90 secs 0.5 = 6.3ppm (gain 2.9ppm)
3) Further 90 secs 0.5 = 9.1ppm (gain 2.80ppm)
4) Further 180 secs 0.5 = 13.6ppm (gain 4.5ppm)

Conclusion 6 mins at 0.5ppm = gain of 10.20ppm.

With the equipment I`m using on the flow side of things it is quite difficult to measure 0.5 ltrs per min (flow meter is marked from 0 to 14) so may have to get another flow control meter or inline effort.

It would appear pointless using higher flow rates, ie 1 ltr per sec when using 0.5 ltrs per sec achieves a similar result over the course of 90 seconds, the higher flow rate wastes oxygen.
Yesterday 3ltrs used = 6.90ppm............ Today (steps 2 & 3 only) 1.5ltrs used = 5.70ppm or if final measurement taken = 4.50ppm.

As for if it will work in wort? The instructions clearly state for use only in fresh water, there is a conversion table included in the kit for readings taken with seawater at 5ppt salinity intervals upto 40ppt salinity.

To give an idea of the difference it makes with sea water a meter reading of 8ppm decreases as follows:-

5ppt = 7.8, 10ppt = 7.6, 15ppt = 7.3, 20ppt = 7.1, 25ppt = 6.9, 30ppt = 6.8, 35ppt = 6.6 and finally 40ppt = 6.40ppm.

I`m not a chemist but is there anyway of converting ppt of salt into sugars in wort?

Again any suggestions gratefully appreciated

[Martin G]

I'd be fascinated to see some experiments like this on a stir plate and with just air pumped through a scintered block.

I read 'somewhere' about how aquarium bubblers acheived more oxygenation through the movement of water at the surface than through the absorption from the bubbles. As a result I've often wondered if magnetic stirrers really need to go like the clappers or if they can just tick over.

Also wonder if with starters and the first couple of hours of a ferment if a scintered steel stone and HEPA filtered air pump is worth considering if ran continuously, since it seems you will never get to 'toxic' levels of oxygen with air alone, but by running for longer are able to replace the oxygen that will be used up in the first half hour if not replaced.

[barneey]

I`ve just finished a brewday today using both conical + oxygen. Will run of some of the wort later to carry out a few tests.

1st test to be carried out is with the wort still left in the boiler.
2nd test to be carried out is with a run off from the conical.

I`ll post the findings later good ot bad..

[barneey]

Tested the wort left in the boiler got a reading of 1.50ppm took a sample from the conical got an even less reading of 1.00, dispite me using oxygen for aeration.

Either the wort is severely un oxygenated in the fermenter or my DO meter doesnt like wort.

Mmmm

[jaybie]

You might find this useful:



JB

[barneey]

Thx for the chart, I`ll do a little reading

[chris2012]

You may be interested in this http://www.brouwland.com/setframes/?l=& ... 4&shwlnk=0

(it mentions about correction for salt water, so i assume it may also handle any correction for wort)

[barneey]

You may be interested in this http://www.brouwland.com/setframes/?l=& ... 4&shwlnk=0

(it mentions about correction for salt water, so i assume it may also handle any correction for wort)

The meter I have, has a chart as list above for Salt water corrections, the next brewday I`ll try again with the meter to see if I can get any sort of reading.

Cheers