Abstract:Abstract: Gas roots meters is a displacement type flowmeter, according to the methods of indication error calculation can be divided into the gas roots meters of class A and class B.Of the Gas Roots Meters of class A,the indication error calculation is based on the meter K coefficient; Of the Gas Roots Meters of class B,the indication error calculation is based on the accumulated flow. Of these two types of Gas Roots Meters, the analysis method of uncertainty is different.