NTEP Column- What Testing Does NTEP Perform?
40 Celsius/ 104 Fahrenheit then two at ambient temperature again. The temperature effect on zero is also evaluated during the environmental testing. A weight of 20 divisions is placed on the scale and the amount of drift during the change in temperature is evaluated. The scale is moved from the environmental chamber to the permanence test equipment. The permanence tester is a device that will apply half of the scale’s weight capacity to the scale 100 000 times to replicate usage. Once the 100 00 cy- cles have been completed an increase /decrease and shift test are performed again. The scale will have more than 20 increase/ decrease tests dur- ing the performance testing and the scale must maintain acceptance tolerance throughout all of the testing. The operational part of the testing is referred to as the “checklist” The checklist verifies all items for an instrument that are not performance relat - ed. The checklist from publication 14 for digital electronic scales is very thorough and 129 pages in length, not every page applies to every device evaluated since the checklist covers from class I thru class IIII devices. Here is a list of some of the items that will be evaluated when a device undergoes NTEP evaluation. Device Markings: Are the markings/identification, correct? Is there a place for the NTEP CC number and is all the required information there? Is the label durable and permanent in nature and does it show tam- pering when removed? Sealing: What is the method of sealing, physical or elec - tronic? What is the sealing category, is it cate - gory 1 category 2, or category 3, and if the in - strument uses an audit trail or event logger does it work correctly?
Jeff Gibson, NTEP Specialist
You know what NTEP is, do you know what NTEP does? This article will give some insight into all the laboratory testing that a 30 lb x 0.01 lb retail computing scale will endure before it is issued an NTEP certificate of conformance. The evaluation of a scale has two parts, the first is performance testing and the second is operational testing. First, let’s look at perfor - mance testing. During ambient temperature testing the scale will have four increase/decrease tests per - formed and a shift test performed. Four more increase/decrease tests at ambient temperature are performed when the bubble level’s sensitiv - ity is evaluated. A creep test will be performed between 90 and 100 percent of the scale’s capacity, typically taking half an hour. When the scale is moved into the environmental chamber a portability test is performed which is an increase/decrease test to make sure the scale maintains its accuracy when it has been moved. The scale will have AC voltage tested and if equipped with batteries DC voltage will be test - ed. All voltage variation testing is performed at fifteen percent below the nominal voltage and ten percent above the nominal voltage. For en - vironmental testing, there are two increase /de- crease tests at ambient temperature then two at minus 10 Celsius/ 14 Fahrenheit then two at
8 NCWM-News
2023 Issue 3
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