信号源内阻限制：ON状态电压20V DC时，1kΩ(大值)；OFF状态电压60V dc时，100kΩ(小值)。 7.输出信号 8路通道，施加电压60V DC(大值)。负载电流：稳态时，每一通道2.25A DC(大值)，每个组件12A DC(大值)，浪涌时，每一通道10A DC(大值)，大持续时间20ms。负载短路持续时间不定(过载时额定切换开关1s内关闭)。电感性负载，在负载上需跨接保护二级管，二级管必须有耐大可能的负载电流的能力，并耐压大于1.3倍的供电电压。 8.电气特性 各类输入输出卡件的电气特性为每路通道独立电气隔离，对模拟量输入/输出信号采用变压器耦合与光电隔离，且每路A/D和D/A转换独立。 所有进出系统的输入输出信号能达到ANSI 37.90抗冲击测试的要求。 9.现场仪表的直流供电 系统可以对所有的现场变送器供电，电压在24~42V之间可调并稳压。因为是通过FBM的端子向现场变送器供电，所以不需要额外增加任何的电源。 FBM卡件的带负载能力特别强，通道的输入阻抗只有50Ω，在实际应用中，可以拖带超过1100Ω的负载。在扣除变送器负载和安全栅负载以及导线电阴后，还有很大富余，增强了信号抗干扰的能力。 三 锅炉DCS系统中使用的Foxboro I/A控制组态模块 Foxboro I/A系统控制软件是在控制处理机CP中进行组态和运行控制的，其中包括如下诸多模块。 (1)ACCUM积算模块：用于计算模拟型输入信号(流量或脉冲数)的累计值，可以串接起来使用。其中MTRFAC是输入信号要转换成输出累计值时所需乘上的一个“倍率因子”，使得输入信号的单位与输出的积算值单位匹配。参数PCNTOP被组态为1时，模块作为一个计数器，可积算输入脉冲信号的脉冲数。 (2)AIN模拟信号输入模块：用于处理FBM的输入信号，同时提供对输入信号修正、滤波，输出保持上次正常值，标度输出到所要求的工程单位，输入通道故障报警，超量程及高/低值报警等功能。 (3)AINR冗余的模拟信号输入模块：用于处理来自冗余的模拟量输入类型的现场总线I/O组件FBM的输入信号，其他功能与AIN模块相同。
Internal resistance limit of signal source: 1K Ω (maximum value) when the voltage in on state is 20V DC; 100k Ω (minimum value) when the off state voltage is 60V DC. 7. Output signal has 8 channels, and the applied voltage is 60V DC (maximum). Load current: 2.25A DC (maximum value) for each channel and 12a DC (maximum value) for each component in steady state; 10A DC (maximum value) for each channel in surge with maximum duration of 20ms. The duration of load short circuit is uncertain (the rated change-over switch is closed within 1s in case of overload). For inductive load, it is necessary to jumper the protective secondary tube on the load. The secondary tube must have the ability to withstand the maximum possible load current and withstand a voltage greater than 1.3 times the supply voltage. 8. Electrical characteristics the electrical characteristics of various input and output cards are independent electrical isolation for each channel, transformer coupling and photoelectric isolation for analog input / output signals, and independent A / D and D / a conversion for each channel. The input and output signals of all incoming and outgoing systems can meet the requirements of ANSI 37.90 impact test. 9. The DC power supply system of field instruments can supply power to all field transmitters, and the voltage can be adjusted and stabilized between 24 ~ 42V. Because the field transmitter is powered through the terminal of FBM, there is no need to add any additional power supply. FBM card has particularly strong load carrying capacity, and the input impedance of the channel is only 50 Ω. In practical application, it can carry more than 1100 Ω load. After deducting the transmitter load, safety barrier load and conductor cathode, there is still a lot of surplus, which enhances the anti-interference ability of the signal. Foxboro I / a control configuration module used in the third boiler DCS system Foxboro I / a system control software is configured and operated in the control processor CP, including the following modules. (1) Accum integration module: used to calculate the cumulative value of analog input signal (flow or pulse number), which can be connected in series. Mtrfac is a "magnification factor" to be multiplied when the input signal is to be converted into the output cumulative value, so that the unit of the input signal matches the unit of the output cumulative value. When the parameter pcntop is configured as 1, the module can be used as a counter to accumulate the number of pulses of the input pulse signal. (2) It is used to correct the input / output signal of FBM and the required input / output signal of the last engineering unit, and to correct the input / output signal of FBM. (3) Ainr redundant analog signal input module: it is used to process the input signal from the redundant analog input type fieldbus I / O component FBM. Other functions are the same as those of AIN module.
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