XPost: sci.electronics.equipment   
   From: presence@MUNGEpanix.com   
      
   In sci.electronics.equipment Ralph Mowery  wrote:   
   > In article , nobody@nowhere.com says...   
   >>   
   >> You keep saying that it's only the accuracy that matters. That's   
   >> true to some - and only some - extent.   
   >>   
   >>   
   >>   
   >   
   > Sometimes it is precision.   
   >   
   > I worked at a company making polyester from raw materials.  In a room   
   > was a panel with about 10 temperature gauges.  At a certain time all   
   > gauges were marked and a sample of the material was sent to the lab.  If   
   > it came back good, then the object was to keep all the gauges on the   
   > mark.  It did not matter how far off the gauges were from the actual   
   > temperature.  No mater how well we calibrated the guages there were   
   > several other factors that we had no control over. Such as the   
   > thermocouples they were connected to.  The specifications were +- 3 deg   
   > C. on the thermocouples from the factory.   If the  temperature varied   
   > more than 1 deg C at 300 deg C it could mess up the material.   
   >   
   > So the object was precision and not accuracy.   
      
   If the goal was keep the needle on their marks it does't have to mean   
   anything was precise. Maybe your guages had no faces, or read mA instead   
   of degrees, and bent needles. As long as your +/- 3 degree thermocouples   
   and controllers did not jump up and down + and then -3 degrees all the   
   time, you were good.   
      
   It's like the zener diode or voltage standard that came up in this thread.   
   Those have no precision. They may not even be accurate. They might be   
   consistent though. Accuracy and precision by themselves can be useless   
   where time or multiple readings are needed.   
      
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