Start with the configured transfer function
This guide applies when the selected output is configured as a linear mapping from 4 mA at the lower range value to 20 mA at the upper range value. Fluke's loop-device testing guidance describes these endpoint checks. Confirm the actual transfer function before using the formula; a different configured mapping needs its own calculation. The lower range value need not be zero.
Keep the 4 mA offset and the 16 mA span
Let I be the measured current in mA, LRV the engineering value at 4 mA, and URV the engineering value at 20 mA. For the stated linear mapping:
Engineering value = LRV + ((I − 4) / 16) × (URV − LRV).
The denominator is 20 − 4 = 16 mA. Dividing the current directly by 20 mA drops the lower-end offset. Save the formula and both endpoints with the channel record, including the unit and 压力 reference where relevant.
A labelled calculation example
Assume a hypothetical channel configured for 0–10 bar(g). This example is arithmetic, not a WESIVO product range, test result or recommended operating 压力.
- 4 mA corresponds to 0 bar(g).
- 8 mA corresponds to 2.5 bar(g).
- 12 mA corresponds to 5 bar(g).
- 16 mA corresponds to 7.5 bar(g).
- 20 mA corresponds to 10 bar(g).
At 12 mA, the fraction is (12 − 4) / 16 = 0.5. A receiver using different endpoints will display a different engineering value even when it reads the same current correctly.
Check scaling at one deliberate location
Write down whether the input card, 控制器 program or display performs the conversion. Avoid applying the same engineering conversion twice. If the receiver uses raw 数字式 counts, obtain its documented count-to-current relationship first; raw counts are not mA. Keep the original input value and the converted value available for the channel check, with the actual configuration version.
Preserve signal status separately
WIKA's signal-clamping explanation shows that output behaviour outside the nominal measuring range depends on the device and its signal limits. Use the selected 仪表 and receiver documentation to define the status rules. Do not interpret every out-of-span current as an ordinary process value, or silently turn it into a plausible endpoint reading. This guide does not assign universal alarm-current thresholds or add a signal-clamping feature to a WESIVO model.
A receiver test and a 传感器 test answer different questions
Test the receiver against the expected values under the site's approved procedure and retain the result. Verify the transmitter's response to the measured physical variable as a separate activity, using an agreed method and reference. Passing a current-input check does not establish the 压力 or 温度 accuracy of the complete installed channel. After a range change, review the transmitter configuration and receiver mapping together.
Apply only to confirmed WESIVO configurations
Published TT248H information confirms 4–20 mA with HART for a 温度-transmitter 模块. The 700 压力-传感器 family has published catalogue and user-guide entries; confirm the ordered version's output and endpoints before applying this guide. A family name or 压力 range is not enough to identify a current interface. Send the complete configuration, connection drawing, range, unit and receiver type with an inquiry.
先确认所配置的传递关系
本文适用于所选输出已配置为线性对应：4 mA 表示量程下限，20 mA 表示量程上限。Fluke 回路设备测试说明介绍了这两项端点核查。使用公式前应确认实际传递关系，其他配置需要采用相应计算方法；量程下限不一定为零。
保留 4 mA 偏置与 16 mA 跨度
设 I 为以 mA 表示的实测电流，LRV 为 4 mA 对应的工程量，URV 为 20 mA 对应的工程量。对于上述线性关系：
工程量 = LRV + ((I − 4) / 16) × (URV − LRV)。
分母为 20 − 4 = 16 mA，直接将电流除以 20 mA 会遗漏下限偏置。应把公式和两个端点与通道记录一起保存，同时记录单位；涉及压力时还应记录压力基准。
明确标注的计算示例
假设某个通道配置为 0–10 bar(g)。以下仅为数学算例，不代表 WESIVO 产品量程、测试结果或建议工作压力。
- 4 mA 对应 0 bar(g)。
- 8 mA 对应 2.5 bar(g)。
- 12 mA 对应 5 bar(g)。
- 16 mA 对应 7.5 bar(g)。
- 20 mA 对应 10 bar(g)。
12 mA 时比例为 (12 − 4) / 16 = 0.5。即使正确读取同一电流，采用不同端点的接收端仍会显示不同工程量。
明确在哪一处完成缩放
写清转换由输入卡、控制器程序还是显示器完成，避免重复进行同一次工程量换算。若接收端使用原始数字计数，应先获取其文件规定的计数与电流关系，不能把原始计数当作 mA。通道核查时应能查看原始输入与转换结果，并保留实际配置版本。
单独保留信号状态
WIKA 的信号限幅说明指出，超出标称测量范围后的输出行为，与设备及其信号限值有关。应依据所选仪表和接收端文件定义状态规则，不能把所有界外电流当作普通工艺值，也不能默默替换为貌似正常的端点读数。本文不规定通用报警电流阈值，也不为 WESIVO 型号增加未经确认的限幅功能。
接收端核查与传感器核查回答不同问题
按现场批准的流程核对接收端预期显示并保存结果；变送器对实际物理量的响应则采用约定方法和参考，单独验证。电流输入核查通过，不能证明整套已安装通道的压力或温度准确度。改变量程后应一起检查变送器配置和接收端映射。
仅应用于已确认的 WESIVO 配置
已发布 TT248H 资料确认该温度变送器模块具有 4–20 mA 配 HART。700 压力传感器系列有已发布样册和用户指南入口，使用本指南前应确认具体订购版本的输出与端点。仅凭系列名称或压力范围不能识别电流接口；询价时请提供完整配置、接线图、量程、单位和接收端类型。
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。