Abstract
With the full start of "National Tenth Five_year Plan",trade of the instruments and meters will have a new increase point. According to the statistics released by relevant aspects. Various types of flux, pressure,temperature meters ,adjusting control meters, analyse instruments ,execution parts and host control system worth 10 billion yuan will be applied to "first period" of The project of West Gas To East. The synthetic evaluation of level of instruments and meters fields of our country has achieved the level of middle of 80's. Microelectronic and computer technology are widely used in the fields of instruments and meters, about 15% of them has been made intelligentized which has achieved the level of 90's.about 30% of them has been made digitalize which has achieved the level of 90's. The products of digitalize, Intelligentize, net, micro- mat ion gradually turn into mainstream. Gaps are becoming wide. problems of reliability, stability are still stand out. Main project's roducts whole set ratio are decreasing (from 80% of Eighth Five_year Plan to 50% at present).High end parts are occupied by foreign products, other products are facing violent impact. After the entry of the WTO, the situation will become even harder. So research and design of instruments and meters of independence information property rights will become urgent affairs.Smart transmitter with HART protocol as a transition product from analog meters to digital meters, for it has become the industry standards and it is fit to the situation of china. Also it can accumulates experiences for FF BUS products. So it still has exploitation value. The nodus of two_wired HART transmitter: typical low powered demand, self_current not more than 3. 5mA;digital signal breadth 1mA (Ipp) in loop; communication between transmitter and operator. By hard work, manufacture one transmitter, reach advance level of our country.
Keywords: HART Protocol; Smart transmitter; Numerical data communication