National metrology institute (NMIs) has the prime responsibility to design, development and maintenance of the primary pressure standards to establish the traceability chain for the calibration of the sophisticated industrial instruments using various pressure standards like ultrasonic interferometer manometer (UIM), air piston gauge (APG), force-balanced piston gauge (FPG), and optical interferometer manometer (OIM). The UIM is one of the most accurate pressure standards in the liquid column manometer category, with the expanded relative uncertainty obtained as 7.2 ppm (k = 2) of the reading in the pressure ranges from 1 Pa to 130 kPa. However, due to the toxicity of mercury and complexity in handling, most of the NMIs have been decommissioned the UIM. For the realization of Pascal in a quantum manner, some of the NMIs have been developing new pressure standards based on the Fabry–Perot interferometer. Some of them have established highly accurate dimensionally traceable piston gauges as a primary pressure standard. Barometric pressure metrology, National Physical Laboratory, India (NPLI) is also trying to develop a Fabry Perot interferometer-based pressure standard. The APG has been working as a reference pressure standard at NPLI since 2002 using UIM as a traceability source, having the expanded relative uncertainty of 12 ppm (k = 2) of the reading. However, recently, NPLI has established the APG as the primary pressure standard in the ranges from 6.5 to 360 kPa with the expanded relative uncertainty as 76 ppm (k = 2) of the reading contained by limitation in the measurement of dimension metrology. To further strengthen the low-pressure range, the FPG has provided traceability in the pressure range of 1 Pa—15 kPa, having expanded relative uncertainty of 25 ppm (k = 2). These pressure standards, i.e., UIM, APG, and FPG, have gone through many critical comparisons, bilateral comparisons, and internal calibrations to establish calibration measurement capabilities (CMCs). This review article presents the journey of design, development, and maintenance of these standards worldwide with special attention at NPLI.

国家计量学会（NMI）负责设计，开发和维护主要压力标准，以建立可追溯链，以使用各种压力标准（例如超声波干涉仪压力计（UIM），空气活塞压力计（ APG），力平衡活塞式压力计（FPG）和光学干涉仪压力计（OIM）。UIM是液柱压力计类别中最准确的压力标准之一，扩展的相对不确定度为7.2 ppm（k = 2）在1 Pa至130 kPa压力范围内的读数。但是，由于汞的毒性和处理的复杂性，大多数NMI已退役UIM。为了以量子方式实现Pascal，一些NMI一直在基于Fabry-Perot干涉仪开发新的压力标准。他们中的一些人已经建立了高度精确的尺寸可追溯活塞表作为主要压力标准。印度国家物理实验室（NPLI）的大气压力计量学也正在尝试开发基于Fabry Perot干涉仪的压力标准。自2002年以来，APG一直使用UIM作为可追溯性源，一直是NPLI的参考压力标准，其相对不确定度扩大了12 ppm（k = 2）的读数。但是，最近，NPLI已将APG确立为6.5至360 kPa范围内的主要压力标准，并且 由于尺寸计量学的局限性而使相对不确定度扩大到读数的76 ppm（k = 2）。为了进一步加强低压范围，FPG提供了在1 Pa-15 kPa压力范围内的可追溯性，并扩大了25 ppm（k  = 2）的相对不确定度。这些压力标准（即UIM，APG和FPG）经过了许多关键的比较，双边比较和内部校准，以建立校准测量功能（CMC）。这篇评论文章介绍了在全球范围内设计，开发和维护这些标准的过程，并特别关注了NPLI。