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目前工业现场中,测量蒸汽、空气、氮气和水等介质的流量,常用的是节流装置配以差压变送器和积算仪组成的流量测量成套装置。节流装置的设计、制造和安装必需符合国标GB 2624-81标准。差压变送部分一般采用DDZ-Ⅱ型带矢量机构力平衡原理的差压变送器。积算仪部分一般采用电子式具有开方和积分功能的积算仪;既能显示被测介质的瞬时流量,又能显示一段时间内的累计流量。由以上三部分组成的流量测量成套装置(简称成套装置)在测量介质的流量时,其使用精度由节流装置、差压变送器和积算仪的基本误差而定。根据GB 2624-81标准第6.3款规定,节流装置配以差压变送器部分测量介质流量时,其标准误差的相对值(σ_(qm))/(q_m)用下式估算:(σ_(qm))/(q_m)=±[((σ_α)/α)~2+((σ_ε)/ε)~2+4((β~4)/α)~2((σ_D)/D)~2+4(1+(β~4)/α)~2((σ_d)/d)~2
Current industrial scene, the measurement of steam, air, nitrogen and water and other media flow, commonly used is throttling device with differential pressure transmitter and calculator composed of flow measurement device. Throttling device design, manufacture and installation must meet the national standard GB 2624-81 standard. Differential pressure transmission part of the general use of DDZ-Ⅱ type with force balance principle vector differential pressure transmitter. Totalizer part of the general use of an open square and integral function calculator; both to show the instantaneous flow of measured media, but also shows the cumulative flow over time. Flow measurement from the above three sets of devices (referred to as complete sets of devices) in the measurement of media flow, the accuracy of its use by the throttling device, differential pressure transmitter and calculator basic error may be. According to the standard of GB 2624-81, section 6.3, the relative standard error (σ qm) / (q_m) when the throttling device is equipped with differential pressure transmitter to measure the medium flow rate is estimated by the following formula: (σ_ (q_m)) / (q_m) = ± [(σ_α) / α) ~ 2 + (σ_ε) / ε) ~ 2 + 4 (β_4) / α) ~ 2 ((σ_D) / D) ~ 2 + 4 (1+ (β ~ 4) / α) ~ 2 ((σ_d) / d) ~ 2