Densitometer vs. Hydrometer

[Rob]

I'm looking for comments on which device is preferred for proofing. The price difference is pretty obvious. What about other differences, advantages, and disadvantages?

[bluestar]

Do you mean an Anton Paar densitometer versus a calibrated glass float hydrometer?

[Etohchem]

I have used several densitymeters in my career. The only one I would ever buy again is an Anton Paar. They are rugged and accurate and fairly quick. The handheld unit is pretty good and one I have used for quick assesment when doing cuts and transfers. Butfor guaging,I only uise the benchtop models.

As far as hydrometers, they are cheaper, quicker, and more portable. However they take practice and are fragile. They are realtivley accurate if people are taught correctly and use the proper technique.

If you can afford it I suggest the AP, but only if you have the expendable cash. Hydrometers are just so much cheaper.

Truman

[Rob]

Bluestar, the Anton Paar densitometer is what I was referring to. However, I didn't want to specify just this brand in-case there are other brands people are using. According to Truman, it sounds like they are the best.

Truman, Any specific benchtop Anton-Paar model that you like the best?

[bluestar]

Not only is Anton Paar the best, for all practical purposes they are the only real choice because the resonant quartz u-tube they are based on remains a patented technology with no real competition. But the handheld and cheaper desktop units ARE NOT acceptable by the TTB for tax purposes. I have recently verified this by correspondence. The problem is that they are not quite as accurate as required. Sadly, I think Anton Paar could correct this by simply improving the cheaper units to provide a 2-3x increase in accuracy and certify it. You have to go to the next level desktop units, and the TTB itself uses the top end unit, which is 10-20x more expensive than the hand held, which is 50x more expensive than a NIST-IRS certified hydrometer. So, most compromise: get the hand held Anton Paar for $3K and get a set of NIST-IRS certified hydrometers for a few hundred dollars. Use the densitometer for working assessments, and verify and certify with hydrometer measurements when required by the TTB. The densitometer measurements take 10 seconds. The hydrometer measurements take a few minutes and some calculation.

[Etohchem]

Bluestar has it right. I would disagree on the time. Average benchtop time for analysis is 6 minutes and removing air by sonicaiton or vacuum can help accuracy. the handhelds are a bit quicker but when doing multiple samples and with practice hydrometers are faster. I have done time studies to show emplyee's that very fact.

as for model. the TTB has certified only a coule of AP models . I, the TTB use and the newest model is the 5000.

as far as using certified equipment...

I was in method develpment on % alcohol for a new product and spoke with Norma Hill the compliance director at the TTB lab in California. she told me that she didn't care if we waved a magic wand and shook a dead beaver at the sample to get an answer. if my results didn't match her's, we were wrong. If my results matched hers, we were right.

from that I take it as you will get a better warm and fuzzy feeling using certified equipment, If you are comformtable using the handhelds to report so be it, but as I remember AP only guarantee's the accuracy of the handheld to 0.1%ABV that is darn close to your tolerance of 0.15%ABV. to close for me to rely on for reporting.

[Etohchem]

also there are other brands, Mettler Toledo, Shimadzu to name a few. But they are using Anton Paar technology and quite frankly the MT unit I used was fragile and had a lot of down time. Also the AP unit uses 2 temperature blocks for faster analaysis. I had a shimadzu unit in for tryout some 10 years ago and was not impressed.

They may have improved or even quite making them, I have never looked past AP since. AP invented the technology and the only ones to get their equpiment certified for use by the TTB.

final word from me AP are great for worry free, repeatable, low training, and accurate analysis. Hydrometers are accurate, the original method and cheap. Hydrometers are fine but get a density meter if you can afford it.

[bluestar]

Agreed, repeated measurements on handheld AT will make it a minute or two, and if you run the desktop, it could be more than a few minutes. But I am surprised the hydrometer is comparable: the time it takes for temperature equilibration, temperature measurements, good practice of three repeat measurements, and the correction calculation is replaced by the integral temperature, averaging, and correction built into the AT. At least, I can't do it that fast.

But final conclusion is the same. Get the AT you can afford, and if it is just the hand held, augment with the hydrometer.

You might be right, you don't need to get the certified hydrometers per se, but I have only seen the accuracy required in certified hydrometers, and you have the advantage that they usually require either no correction, or a limited correction that is valid over the measurement range. None of the cheap hydrometers will do that.