WorldWide Drilling Resource

Do We Really Need This Level of Accuracy or Precision? by Britt Storkson Owner, P2FlowLLC The words accuracy and precision are very similar, but not the same. Wikipedia defines the accuracy of a measurement system as the degree of closeness of measurements of a quantity to that quantity's actual (true) value. The precision of a measurement system, re- lated to reproducibility and repeatability, is the degree to which repeated meas- urements under unchanged conditions show the same results. Accuracy is sort of a “tolerance” of what we can accept for whatever we’re doing, and it is usu- ally expressed as a percentage of ideal. Fo r examp l e , i n electronics, i f a 100-ohm resistor has a 5% toler- ance, it means the actual resistance value could vary f r om 9 5 t o 1 0 5 ohms. Su r e we l i ke everything to be as accurate as possi- b l e , b u t h i g h e r accuracy always comes with a high- er price. But some- t i me s w e d o n ’ t need great accura- cy. Take your auto- motive fuel gauge. You are probably lucky if this fuel gauge has +/- 20% accuracy...mean- ing, what it says on t h e f u e l g a u g e could be up to 20% off of what the real reading is. Let’s not berate t he ca r compa - nies for selling us such poor-quality fuel gauges, be- cause your fuel gauge does not need to be that accurate. You just n e e d t o k n o w about how much fuel you have left in your tank - not the exact quantity of fuel. Plus, the 20% accuracy fuel gauge would cost the car manufac- turer perhaps $1, whereas a more a c c u r a t e f u e l gauge could cost $50 or more. As long as it’s rea- sonably durable and consistent, most car owners wi l l accep t t he l ess expens i ve gauge. Giving you a 20%accurategauge, the carmaker isn’t selling you a flawed product. It’s a question of if you really need the level of accuracy. If you don’t really need the level of accuracy, then don’t spend the money for it. You, as a car buyer wanting the lowest price, and the car manufacturer wanting the high- est profits from the sale of the car, motivates the car builder to choose the less expensive gauge; and the less expensive gauge does not degrade the safety or performance of the car. We make a floatless tank fill control unit which uses the pressure of the water to determine the water level in the tank. This works because the higher the water column, the higher the pressure at the bottom of the column. This has a lot of advantages because there is nothing in the storage tank. No wires, electric power, antennas, or other equipment is needed at the storage tank. The storage tank can be ¼ mile or more away from the pressure sensor and/or fill pump, and it still works. If your tank is belowground, 72 SEPTEMBER 2014 WorldWide Drilling Resource ® 0,2+ 675;,4 -57 5;,7 ',(78 /558, -753 +0--,7,49 35+,28 95 -09 >5:7 4,,+8 "(4.04. -753 36 95 36 4*2:+,8 %,/0*2, :36 #9(7904. (99,7> /(7.04. (4+ (4+ % 95 65<,7 &07,-,,+,78 0. (7708 "5(+ ,74+(2, ,< '571 $,2 (= &,) 809, <<< .,9,* *53 3(02 8(2,8 .,9,* *53 ',(78 5- =6,70,4*, 3(1, 9/08 204, 5- &,2+,78 (4 :43(9*/,+ !:(209> 75+:*9 04 95+(>?8 3(71,9 690548 04*2:+, 49,74(2 7,88:7, 536,48(904. 25< 549752 67,;,4904. (**0+,49(2 5;,786,,+ +(3(., 95 9/, &,2+,7 %,/0*2, :36 #9(7904. %5298 ( ,9,* ,=*2:80;, (99,7> /(7.04. %5298 (4+ % 95 65<,7 >5:7 0. :4 &07,-,,+ 589 536(*9 >+7(:20* &,2+,7 54 (71,9 (049,4(4*, 7,, ,80.4 0./9,89 >+7(:20* &,2+,7 54 (71,9 Storkson cont’d on page 78.