This paper describes the accurate determination of pressure in the range 10− 3–10− 6 Torr
(∠ 10− 1–10− 4 Pa) by a bakeable McLeod gauge using variable compression technique. A
thorough investigation of two major aspects of pressure determination by a McLeod gauge,
ie, capillary depression phenomena and mercury vapor stream effect, has been made. The
capillary depression phenomena in the wide bore reference arm tube has also been taken
into account in determining the capillary depression correction in the compression capillary …