Frivolous Friday Fun – Using the Freedom of Information Act to get a Beer Recipe

Here’s an interesting way to get a beer recipe: file a request with the US Federal Government via the Freedom of Information Act! It may seem strange, but that’s exactly what someone did to get the recipe for President Obama’s beer. Apparently the President enjoys a variety of beers made with honey from the White House beehives. The request worked, and the President has agreed to make the recipes available soon.   A link to the story can be found here.

I also want to apologize to at least one of my friends for my post on August 17th. I provided a link to a list of beer “trivia,” most of which was completely false – hence my idea that it was weird enough for a “Frivolous Friday” post. However, the whole point of this blog is to provide accurate, helpful information to brewers everywhere. There’s enough downright wrong information floating around out there, and I don’t want to do anything that might be seen as encouragement of inaccurate or negative commentary on any beer or brewery, even in the context of humor. For those who have to do battle for the truth, I recognize that it’s not funny at all, and I am sincerely sorry.

 

 

 

Electrochemical Oxygen Sensors – Are they obsolete?

I am still a huge fan of Electrochemical (EC) Oxygen sensors. They’re the best choice for many applications, and because they’re analog and not digital, they provide a real-time signal that’s free from digital noise.

Just like optical dissolved oxygen sensors, electrochemical dO2 sensors measure the partial pressure of oxygen. That number is then used in conjunction with Henry’s Law to calculate the solubility of oxygen in the liquid. For a more complete explanation, see the blog post at this link. The difference between an optical and an electrochemical sensor lies in the mechanism for determining the O2 reading.

While optical sensors use a fluorescent coating and light to measure the quenching properties of oxygen, EC sensors use a polarized cell that measures the electrochemical response of oxygen.  An electrochemical oxygen sensor, also called a Clark-type or polarographic detector, uses electrochemistry to reduce oxygen. This reduction of oxygen creates a current proportional to the partial pressure of the O2 content of the sample being measured.

At its core an EC sensor is a pair of dissimilar metal electrodes bathed in a conductive electrolytic solution.  A membrane covers the electrodes, and oxygen from the sample permeates through the membrane to the electrode where it is reduced.  The electrodes are polarized with about 0.6 volts of electricity, but no current flows between them unless there is oxygen available to carry out the electrochemical reaction.

What could be the downside of an EC sensor? Over time, the electrodes may get fouled due to by-products of the reaction. If this happens, the response time of the sensor gets slow until it reaches the point where resistance builds up in the cell and the measurement becomes inaccurate.  As a general rule, when EC sensors fail they fail with low readings.

So what about areas where EC sensors excel? I really like them in applications where I need wide dynamic range.  I can use the same analyzer to tell me whether I’m reading 0.001 ppm or 20.0 ppm. If I need to track changes quickly in situations where the noise from an optical probe would be too great, or if I’m in the gas phase and reading less than 0.001% O2, I prefer to use EC sensors.

If you’re measuring TPO using the Hach 6110 TPO analyzer, then an EC probe is the only way to go. The 6110 only measures in the gas phase, first giving a discrete headspace O2 and then giving a discrete dO2 concentration. An optical sensor just won’t work in this situation, because the response is not fast enough to properly track the constantly changing sample as gas is released out of the package.

My final thought is that for most applications, optical sensors are usually the best option. But when you want a wide dynamic range or continuous measurement, electrochemical sensors can’t be beat.

Frivolous Friday Fun – Trivia vs. Bad Rumors

 

I’m always amused by the amount of bunk that flows about on the internet. While looking for something senseless to use for today’s topic, I came across a website professing to have accurate beer trivia. Much of it seems plausible, but a few of the “facts” are just a tad bit suspect. If you have any insight into this, leave a comment. I’m especially curious about the truth to the Michelob myth. You can find the link here.

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