March 2006 

Suitability of Installation and Variations of Weighing and 

Measuring Devices Covered by an NTEP CC 

By Steven Cook 

As part of any field examination of a weighing or measuring device, a field inspector 

must determine whether or not the device is “suitable” for the application. In addition to 

the suitability requirements included in the General and specific codes in NIST 

Handbook 44, inspectors in a jurisdiction that require National Type Evaluation Program 

(NTEP) Certificates of Conformance (CCs) must determine whether or not the device and 

its application are covered under a current CC. 

The NIST Weights and Measures Division (WMD) frequently receives questions about 

how to determine if a specific device with a CC is covered by the CC when it: 

• is used in an application not listed on the CC; 

• has metrological parameters not listed on the CC; 

• is modified by the original equipment manufacturer, service agency, or the user; or 

• is repaired or remanufactured. 

Ultimately, the decision of whether or not a specific device is covered by a CC rests with 

NTEP. 

Background on Type Evaluation: Type evaluation can be defined as a systematic 

examination and testing of the performance of one or more weighing or measuring 

devices of an identified type (pattern) against documented requirements in NIST 

Handbook 44 and NCWM Publication 14. The results of the evaluation are used to 

determine whether a CC may be issued for the type. The holder of the CC is expected to 

report to NTEP any metrological and other significant changes to the type that may 

warrant a change to the CC and/or additional evaluation. Examples of metrological 

changes are discussed later in this article. 

It should also be noted that CCs are granted to specific applicants. Seemingly identical 

instruments produced by different manufacturers must each have an NTEP CC. 

Additionally, other companies or distributors may enter into an agreement with the 

original holder of the CC to market the NTEP-certified device under the distributor’s own 

brand, designation, or company name. In these cases it is the responsibility of the 

distributor to acquire and maintain a separate NTEP CC. 

Contents of the CC: A CC typically includes identification of the type along with 

information about specific model designations, description of the type, markings, 

inscriptions, specifications, etc., including, if applicable, the accuracy class. In the case of 

a family of devices, element, or a family of elements, CCs typically list minimum and 

maximum values for metrologically significant parameters such as division sizes, number 

of divisions, flow rates, types of products weighed or measured, capacities, meter and 

scale dimensions, and number of products or load-receiving elements that can be 

operated by a single indicating element. Information is also provided about the intended 
use of the device, elements, or system. Additionally, the CC includes information on the 

evaluations performed on the equipment submitted for testing and/or suitable documentation used to verify compliance with applicable requirements in NIST Handbook 44 and 

National Conference on Weights and Measures (NCWM) Publication 14. 

Suitability of the Application: The inspector should take into consideration both the 

NIST Handbook 44 suitability requirements and contents of the CC to the extent that is 

possible. The following are some general guidelines for determining if the device is 

suitable for a specific installation and is covered by the CC. 

In determining if a device is suitable for a specific application, the field inspector should 

apply NIST Handbook 44 General Code paragraph G-UR.1. “Selection Requirements” 

and other suitability requirements in the specific codes, as applicable. In addition, the 

inspector should review the most current CC for the device. As mentioned earlier, the 

various applications in which the manufacturer intends to market the device and for 

which NTEP has evaluated the device are listed in the “Application” paragraph on the 

CC. Many times the “Application” paragraph will state that the device may be used for 

“General purpose weighing (or measuring) applications.” This does not imply the devices 

can be used in all applications. For example, devices such as vehicle scales, livestock 

scales, lubricant devices, and retail motor-fuel devices have application-specific 

Handbook 44 specifications, test notes, and tolerances that would not make them suitable 

for other general purpose weighing (e.g., shipping scales) or measuring applications (e.g., 

agri-chemical liquids). 

The inspection of measuring devices should include the different products measured by 

the device in a specific installation. The inspector needs to make sure that each product is 

suitable for the device and that the products measured by the device in normal use in that 

application are listed on the CC. NTEP has developed product tables that classify liquid 

products for various measurement technologies and product applications into “product 

families” and “subgroups.” Each group includes a range of products that can be 

accurately measured by the device. For example, a CC for positive displacement meters 

lists products that are broken down by product families and product subgroups, along 

with examples of typical products and additional parameters such as viscosity, specific 

gravity, and abrasive solids (if applicable). 

The inspector should be aware that some CCs apply to devices covered under productspecific Handbook 44 codes (LPG and Anhydrous Ammonia, Carbon-Dioxide LiquidMeasuring Devices), technology-specific codes (Mass Flow Meters), and applicationspecific codes (Automatic Bulk Weighing Systems and Vehicle-Tank Meters, etc.). A CC 

for a weighing/load-receiving element may list applications under the Scales Code and 

the code for Automatic Weighing Systems. A CC for a liquid-measuring element may list 

applications under the Liquid-Measuring Devices, Vehicle-Tank Meter, LPG and NH3

Liquid- Measuring Devices, and Milk Meters codes. Again, this information should be 

listed on the CC for either the weighing or measuring element, device, or system. 

Additionally, the CC for a system may cite a CC number for a metrologically significant 
element that has a stand-alone CC. For example, an automatic bulk-weighing system CC 

will cite the CC for the load cell(s) used in the load-receiving element for the system. 

Changes or Modification to the Device: Since NTEP only evaluates a limited number 

of devices during the evaluation, a CC alone cannot guarantee that a device in the field 

complies with Handbook 44 and is suitable for the location. The inspector must 

determine if a device is still covered by the CC if the inspector observes what appears to 

be a change to a device during an initial verification inspection or a modification to an 

existing device during a subsequent verification. These would include metrological 

changes which may impact the suitability of the device at a specific installation or bring 

into question whether or not the specific device is still covered by the CC. 

Metrologically significant changes are considered changes to the device that have the 

potential to affect the measurement accuracy, primary indications, accuracy of recorded 

representations of the device, and other changes to the device that can affect compliance 

with Handbook 44. From an NTEP perspective, such variations or changes to the type are 

only covered if they are listed in the applicable CC. 

Many metrologically significant modifications and configurations can be identified by the 

inspector during initial and subsequent verifications. Examples include changing the type 

of load cell mounting hardware, replacing lever systems with load cells, changing the 

capacity or flow rate, adding “dump-through” capability on vehicle or railway track 

scales (emptying bulk material through the scale deck), the addition of livestock racks on 

vehicle scale or other flat platform load-receiving elements, changing conveyor widths, 

and changing the rounding algorithms for mathematical calculations involving 

measurement values. The NCWM is developing initial verification report forms and test 

procedures as part of the Conformity Assessment Process to help the field official verify 

that a specific device complies with the information listed on the CC. The information 

gathered by the states during the initial verification will be used to provide feedback to 

NTEP. 

However, there are other metrological changes that are not always obvious to the 

inspector such as a device’s sensitivity to influence factors (e.g., temperature, voltage, 

and time), construction materials, and measurement technology. The inspector is not 

expected to investigate if these types of metrological changes have been made to the 

device during routine inspections since they need to be verified under controlled 

conditions. Therefore, the NCWM is currently developing a Verified Conformity 

Assessment Program to verify that the applicant has control over the testing for influence 

factor requirements and a “quality system” (i.e., design changes, parts suppliers, 

manufacturing process) during production. 

Superficial differences, also referred to as “non-metrological variations,” include 

different devices produced by a particular manufacturer that are identical in design, 

materials, components, and measurement ranges, but differ superficially in color or other 

non-metrological features such as built-in printers or extra displays. Devices with such 

variations can normally be regarded as being covered by the applicable CC. 
The inspector must also be certain that any metrological modification(s) to the device 

listed above as a result of a repair or remanufacture of the device are still covered by the 

CC. NIST Handbook 130 Uniform National Type Evaluation Regulation Section 4 and 

NCWM Publication 14 - NTEP Administrative Policy (2005) Section M state that if a 

person makes changes to a device to the extent that the metrological characteristics listed 

on the CC are changed, that specific device is no longer traceable to the active CC. If a 

person repairs or remanufactures a device, the device must be repaired or remanufactured 

consistent with the manufacturer’s original design; otherwise, that specific device is no 

longer traceable to the active CC. Please note that there are additional marking and 

definition requirements for remanufactured devices and elements in NIST Handbook 44 

General Code paragraph G-S.1.2. and Appendix D. 

Possible Actions: The inspector should consider the following guidelines when there is a 

question about when a specific device is covered by an NTEP CC. 

Generally speaking, NTEP can be contacted to verify if a specific device is covered by 

the CC, including such issues as whether or not the device is installed in an application 

for which it was not intended or if changes to the device are still covered by the CC. The 

NTEP laboratory that performed the evaluation is another source of information that may 

help determine if the specific device is covered by the CC. The holder of the CC may also 

be contacted to confirm if the CC covers changes made to the device by the user, service 

agent, or service agency, or if the specific product application or metrological parameters 

for the specific device were not intended to be covered by the CC. 

If the inspector has determined that the specific device is no longer covered by the CC, 

the inspector should take appropriate actions based upon the Weights and Measures 

statutes, regulations, and policies established by the state and local jurisdiction to resolve 

the situation. The owner of the device should also be notified that the device is not 

considered to be covered by a CC. The owner of the device may choose to contact the 

holder of the CC to discuss solutions that would allow the device to be covered by the CC 

and comply with applicable Weights and Measures requirements. The state or local 

jurisdiction must decide the appropriate solution for devices that are no longer in 

production and/or the holder of the CC is no longer in business. Note that WMD, NCWM 

Inc., and NTEP do not have regulatory authority. WMD can provide information and 

interpretations of applicable NIST Handbooks to the inspector, state, and the local 

jurisdiction. 

For questions about NTEP, including questions on CCs and NTEP technical policies, you 

may contact NCWM Headquarters by phone at 240-632-9454 or by email at 

ncwm@mgmtsol.com. Please contact Steve Cook by phone at 301-975-4004 or by email 

at owm@nist.gov if you have any questions on the information provided in this article.