API MPMS 21.2:1998(R2016) pdf download.Manual of Petroleum Measurement Standards Chapter 21—Flow Measurement Using Electronic Metering Systems
3 Definitions and Symbols
3.1 INTRODUCTION The purpose of these definitions is to clarify the terminol- ogy used in the discussion of this standard only. The defini- tions are not intended to be an all-inclusive directory of terms used within the measurement industry, nor are they intended to conflict with any standards currently in use. 3.2 WORDS AND TERMS 3.3 accounting period: A duration of time usually of fixed length, such as a day or week, or the period of time required to transfer all or part of a batch. 3.4 analog to digital (A/D) converter: A signal proces- sor that converts electrical analog signals to a corresponding digital number. 3.5 accuracy: The extent to which the results of a calcu- lation or the readings of an instrument approach the true value. 3.6 audit trail: The record of an electronic liquid measure- ment (ELM) system containing verification or calibration measurements for all tertiary and secondary devices, actual specifications for the primary device, constant values, times and dates of any changes affecting reported volumes and all documentation required under audit and reporting require- ments; it may also include identification of those making the changes. The audit trail may consist of single or multiple records in electronic or hard copy form. 3.7 batch: A discrete shipment of commodity defined by volume, accounting time interval, or quality. 3.8 calibration: The testing and adjustment of an ELM system or system components to conform with traceable ref- erence standards to provide accurate values over the ELM’s prescribed operating range. 3.9 calibration span: The difference between the cali- brated maximum and minimum range limits. 3.10 certified equipment: Equipment whose perfor- mance is traceable to primary standards maintained by an internationally recognized standards organization, such as the National Institute of Standards and Technology, and that has been provided with documentation (Certificate of Conform- ance) stating the traceability. 3.11 combined correction factor ( CCF ): A factor that combines two or more correction factors that may include a correction for the effect of temperature on liquid ( CTL ), a cor- rection for the effect of pressure on liquid ( CPL ), a meter fac- tor (MF), and others. The intent of CCF is to limit the effects of rounding and truncation errors in volume measurement and proving calculations. See API MPMS Chapter 12.2 for further discussion. 3.12 composite meter factor ( CMF ): A factor that combines a meter factor along with a correction for the com- pressibility of the fluid between normal operating pressure and base pressure. A composite meter factor may be used for meter applications where the pressure is considered constant during the ticket period.