First identify what the current represents
A DP-流量 loop can send a current linear to 差压 压力 and calculate 流量 downstream, or send a current already proportional to calculated 流量. Document the configured variable and the calculation location. A display value, HART variable and analogue output must be checked separately; do not infer their mapping from a screen label.
Yokogawa's FieldGuide describes square-root extraction in either the transmitter or the 控制器, with the operation applied once to the DP-derived value. This is a signal-chain check, not a recommendation for an unverified product feature.
Use a model with explicit limits
For this teaching example, assume zero-based positive DP and 流量 ranges, constant density and effective 流量 coefficient, and operation within the primary element's applicable regime. Exclude low-流量 transition and cutoff behaviour for the ideal calculation.
Let x = DP / DP_max and y = Q / Q_max. Both are dimensionless fractions. Then y = sqrt(x), or x = y².
- Current linear to DP: I_DP = 4 + 16 × x, in mA.
- Current proportional to 流量: I_Q = 4 + 16 × y, in mA.
- If the input current is linear to DP, first obtain x = (I - 4) / 16, then calculate y. Do not take the square root of the current in mA directly.
This is not a complete gas or steam mass-流量 calculation. Changing density, discharge coefficient and other process effects need the actual validated model. Offset ranges, reverse 流量 and device-specific transfer functions require separate treatment.
Build an intermediate-point test sheet
The following values are calculated examples, not WESIVO performance data. Each line states 流量 fraction, required DP fraction, current linear to DP and current proportional to 流量.
- 30% 流量: 9% DP; I_DP = 5.44 mA; I_Q = 8.80 mA.
- 60% 流量: 36% DP; I_DP = 9.76 mA; I_Q = 13.60 mA.
- 80% 流量: 64% DP; I_DP = 14.24 mA; I_Q = 16.80 mA.
- 100% 流量: 100% DP; both currents are 20.00 mA.
For a separate check at 16% DP, the ideal 流量 is 40%. A linear-DP current is 6.56 mA; a 流量-proportional current is 10.40 mA. If downstream logic treats the linear-DP input as 流量 without extraction, it indicates 16%. If it extracts a root from the already 流量-proportional input, it indicates about 63.25%. Both errors disappear at the ideal endpoints, so endpoint-only checks can miss them.
Record the check's coverage
An injected current checks the receiving I/O and downstream calculation. Applied DP checks an additional part of the transmitter chain. Neither alone verifies the primary element or proves actual steam 流量 accuracy. Record the applied quantity, observed current, 数字式 variable, displayed 流量, configuration revision and calculation owner.
Near zero, square-root conversion magnifies small DP changes. The cited low-流量 note discusses device-specific transition and cutoff behaviour. Record the actual threshold, basis and mode; do not apply a universal cutoff or silently turn negative/fault input into valid zero 流量.
For a WESIVO 730E or 780C enquiry, attach the required signal schedule and request confirmation of the ordered output characteristic. The current catalogue is the product reference; this general calculation does not establish built-in square root, compensation or a validated 流量 system for either model.
先确认电流究竟代表什么
差压流量回路可以传输线性差压电流，由下游计算流量；也可以传输已经对应计算流量的电流。应记录配置变量和计算位置。显示值、HART 变量与模拟输出应分别核对，不能仅凭屏幕标签推断它们的映射关系。
Yokogawa FieldGuide 介绍了在变送器或控制器中进行开方、对同一个差压来源的量只开方一次的原则。这里进行的是信号链核对，并非推荐未经确认的产品功能。
给计算模型写清边界
本教学算例假设差压和流量量程均从零开始、流向为正、密度和有效流量系数不变，并处于一次元件适用的工况范围内。理想计算暂不包含小流量过渡和切除特性。
令 x = DP / DP_max，y = Q / Q_max；二者均为无量纲小数，则 y = sqrt(x)，反算为 x = y²。
- 线性差压电流：I_DP = 4 + 16 × x，单位 mA。
- 线性流量电流：I_Q = 4 + 16 × y，单位 mA。
- 输入为线性差压电流时，先算 x = (I - 4) / 16，再求 y；不能直接对以 mA 表示的电流值开方。
这不是完整的气体或蒸汽质量流量计算。密度、流出系数和其他工况影响需使用实际验证的模型。非零起点、反向流和设备专用传递函数应另行处理。
制作中间点测试表
以下均为计算示例，不是 WESIVO 性能数据。每行依次为流量比例、所需差压比例、线性差压电流和线性流量电流。
- 30% 流量：9% 差压；I_DP = 5.44 mA；I_Q = 8.80 mA。
- 60% 流量：36% 差压；I_DP = 9.76 mA；I_Q = 13.60 mA。
- 80% 流量：64% 差压；I_DP = 14.24 mA；I_Q = 16.80 mA。
- 100% 流量：100% 差压；两种电流均为 20.00 mA。
另取 16% 差压作核对，理想流量为 40%。线性差压电流为 6.56 mA，线性流量电流为 10.40 mA。若下游漏掉开方、直接把线性差压输入当流量，会显示 16%；若对已经线性对应流量的输入再次开方，会显示约 63.25%。两类错误在理想端点处消失，只检查端点可能漏检。
说明核对覆盖的范围
注入电流可检查接收 I/O 与下游计算；施加差压会额外覆盖变送器链路的一部分。二者单独均不能验证一次元件，也不能证明实际蒸汽流量精度。应记录施加量、实测电流、数字变量、流量显示、配置版本和计算责任位置。
零点附近，开方会放大较小的差压变化。引用的小流量说明讨论了具体设备的过渡与切除特性。应记录实际阈值、阈值基准和模式，不使用通用切除值，也不应将负输入或故障输入悄悄变成有效零流量。
咨询 WESIVO 730E 或 780C 时，请附所需信号表，要求确认订购配置的输出特性。当前样册是产品依据；这里的通用计算不证明任一型号内置开方、补偿或已组成验证合格的流量系统。
沟通您的应用需求
请提供介质、工况、连接、输出、数量及收货地区，WESIVO 将在报价前核对配置。