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pHaestus · 09-09-2003, 12:41 PM

You realize you are doing this in exactly the wrong manner, right? I would suggest:

1) Come up with goals for the testing
2) Run some numbers with different levels of accuracy in the temperature and flow rate and power measurement.
3) Price out gear that will get you where you want to be error-wise. This will let you meet your goals with the minimum outlay of cash.

I get the impression that your goal in #1 is "to get the exact correct answer", and that's going to result in a $ value for 3 that's near infinity.

I also get the impression that there is a bit of snake oil being sold in this whole WBTA thing. Quality testing just can't be done without a big investment in both time and money.

An allegory for the interested: I recently made some arsenic samples of known chemical composition in my lab. I started with a 1000mg/L standard that I diluted to 0.1 mg/L using an analytical balance accurate to 0.1mg and with density of water adjusted using room temp. I sent these to 4 professional laboratories in my region and asked for As analysis. The point? (1) none of the labs reported 0.1 mg/L (but one was "close enough" with 0.12ppm) (2)%RSDs were 1-2% max (3) there was a range from 0.02 to 0.4mg/l for the concentrations.

So what happened there? Each lab used probably a $100,000 instrument with a professionally trained technician. Each lab had good reproducibility of measurement, and none of the labs were correct.

Rather than spend thousands of posts on talking about the minor details, I would suggest starting with error and uncertainty and how to propagate error forward. That would be my first standard if I were a WBTA; all points must have error bars. Equipment needed would all follow naturally from that standard.

09-09-2003, 12:41 PM	#22
pHaestus Big Player Making Big Money Join Date: Aug 2001 Location: irc.lostgeek.com #procooling.com Posts: 4,782	You realize you are doing this in exactly the wrong manner, right? I would suggest: 1) Come up with goals for the testing 2) Run some numbers with different levels of accuracy in the temperature and flow rate and power measurement. 3) Price out gear that will get you where you want to be error-wise. This will let you meet your goals with the minimum outlay of cash. I get the impression that your goal in #1 is "to get the exact correct answer", and that's going to result in a $ value for 3 that's near infinity. I also get the impression that there is a bit of snake oil being sold in this whole WBTA thing. Quality testing just can't be done without a big investment in both time and money. An allegory for the interested: I recently made some arsenic samples of known chemical composition in my lab. I started with a 1000mg/L standard that I diluted to 0.1 mg/L using an analytical balance accurate to 0.1mg and with density of water adjusted using room temp. I sent these to 4 professional laboratories in my region and asked for As analysis. The point? (1) none of the labs reported 0.1 mg/L (but one was "close enough" with 0.12ppm) (2)%RSDs were 1-2% max (3) there was a range from 0.02 to 0.4mg/l for the concentrations. So what happened there? Each lab used probably a $100,000 instrument with a professionally trained technician. Each lab had good reproducibility of measurement, and none of the labs were correct. Rather than spend thousands of posts on talking about the minor details, I would suggest starting with error and uncertainty and how to propagate error forward. That would be my first standard if I were a WBTA; all points must have error bars. Equipment needed would all follow naturally from that standard.