Dear Drs. Schl $B]U (Jer and Dias, Thank you for your kind answers and suggestions. I am sorry but I probably made a wrong English translation in my previous question. What I want to ask was concerning to the difference in "diameters" of the two capillaries. The lengths of the capillaries were almost the same. In our Combustion III system, however, the diameter of the capillary for sample gas is apparently shorter than that for reference gas. As described by Bob, and also in our service manual, shouldn't they be opposite? I guess the diameter of the capillary for sample gas must be longer to get lower split ratio at open split for sample measurement. Or I make some misleading again? Sincerely, Urumu Tsunogai -------------------------------------------- Urumu Tsunogai, Dr. Sci. Dept. Environ. Science & Technology, IGSSE Tokyo Institute of Technology 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502, Japan Tel. +81-45-924-5555 (or 5554) Fax. +81-45-924-5554 E-mail [log in to unmask] ---------------------------------------------