I appologize if I was too hard on Bill. The fact is that once the units are measuring something they are units of measure. The SI units are the only ones that have a scientific definition and only represent physical properties. The other ones may be unit which relate to *one or a combination* physical properties but they are still units of measure.
Speaking about the drill: I am glad that you agree that these *are* units of measurement. Now here is my answer: First, if you define holes per minute as hpm and you sell to China they would not understand what hpm means. One of the main principles of SI is to be language independent. Second, when you define a unit of measurement you must have a way to measure it. Since all measurements are not made equal the definition of hpm may be extremely relative and ultimately mean nothing. In what conditions, what kind of material is being drilled at what speed, is it a hand drill or a CNC machine? Same thing as with the pages per minute. What paper size? What quality? how many words are there, what's the humidity in the room? (It does matter for the laser printer or you get only jams). These units ultimately reflect some real properties of the printer. The reasons International Standard bodies were invented was to measure only those properties of a machine or tool which are clear an cannot confuse anyone. If I say the diameter is 5 mm with a specified tolerance and the length, and the material of construction are whatever they are then it's up to the user to decide what to buy for his needs. I may ***recommend*** the drill for use on most woods or concrete or whatever but I cannot say it drills at a certain speed whithout needin to give a whole other list of conditions of my testing procedure. Back to the toilet now: Do I understand from your words that GPF would mean some kind of speed? Why the analogy with ml/s? GPF or LPF doesn't mean anything other than the size of the tank. It empties in one flush so what is the difference from just rating the volume of the tank? Is there a NIST specification of the FLUSH as to be happening only in a certain time period? If we want speed that we have to bring the time into the picture. If we had L/s it was another story. That is a SI unit of measurement for flow which will give the opportunity to the customer to compare which system empties faster and which one is slower. So in rating toilets I believe that the (max) volume of the tank in L and the max speed of discharge in L/s or L/min would be the best way to make an educated decision in buying a system. GPF is a major joke. In terms of the printer: I am not a printer engineer but I would assume that if one rated the (max) carriage speed in cm/sec and the (max) ink particle size in ?m it may be a good way to rate a printer. Maybe some manufacturer may want to specify the carriage speeds in both X and Y directions. Fine! Again, I am not an expert but ppm is another joke. I hope this answers this part. Adrian -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Jim Elwell Sent: Wednesday, 30 January, 2002 16:26 To: U.S. Metric Association Subject: [USMA:17774] Re: Democracy and metrication Responding to both of Adrian's posts on this subject. At 04:20 PM 1/30/2002 -0600, Adrian Jadic wrote: >You're in denial Bill! If they are not units of measure what are they? Can >you give me a definition for units of measure? What is the difference >between BTU and flushes? I think Bill has a very valid point. Your comment helps illustrate why: >I was taught that when I build a tool I classify it by the strength of the >material, or by the dimensional characteristics and not by how many holes it >can drill per minute. Now, if I am buying a drill, I would care a lot more about how many holes it could drill per minute than it's dimensional characteristics. So what is wrong with "units" that are useful in the real world, even if they are not somehow tied to fundamental units of measure? Take your toilet example. Switch from "gallons per flush" to "liters per flush" and you have a useful measure with a metric component. No, it is not entirely metric but it provides information the person specifying it needs to know. He may need this info a lot more than (for example) "fills at 50 mL/s." Another example: laser printers are generally rated in "pages per minute." A rather useful figure, and pretty much unrelated to metric or colloquial systems. Adrian, how would you rate a toilet, or a laser printer? Jim Elwell P.S. I've seen the LPF (liters per flush) on many toilets and urinals in the USA.
