信號源內(nèi)阻限制：ON狀態(tài)電壓20V DC時，1kΩ(大值)；OFF狀態(tài)電壓60V dc時，100kΩ(小值)。 7.輸出信號 8路通道，施加電壓60V DC(大值)。負(fù)載電流：穩(wěn)態(tài)時，每一通道2.25A DC(大值)，每個組件12A DC(大值)，浪涌時，每一通道10A DC(大值)，大持續(xù)時間20ms。負(fù)載短路持續(xù)時間不定(過載時額定切換開關(guān)1s內(nèi)關(guān)閉)。電感性負(fù)載，在負(fù)載上需跨接保護(hù)二級管，二級管必須有耐大可能的負(fù)載電流的能力，并耐壓大于1.3倍的供電電壓。 8.電氣特性 各類輸入輸出卡件的電氣特性為每路通道獨立電氣隔離，對模擬量輸入/輸出信號采用變壓器耦合與光電隔離，且每路A/D和D/A轉(zhuǎn)換獨立。 所有進(jìn)出系統(tǒng)的輸入輸出信號能達(dá)到ANSI 37.90抗沖擊測試的要求。 9.現(xiàn)場儀表的直流供電 系統(tǒng)可以對所有的現(xiàn)場變送器供電，電壓在24~42V之間可調(diào)并穩(wěn)壓。因為是通過FBM的端子向現(xiàn)場變送器供電，所以不需要額外增加任何的電源。 FBM卡件的帶負(fù)載能力特別強(qiáng)，通道的輸入阻抗只有50Ω，在實際應(yīng)用中，可以拖帶超過1100Ω的負(fù)載。在扣除變送器負(fù)載和安全柵負(fù)載以及導(dǎo)線電陰后，還有很大富余，增強(qiáng)了信號抗干擾的能力。 三 鍋爐DCS系統(tǒng)中使用的Foxboro I/A控制組態(tài)模塊 Foxboro I/A系統(tǒng)控制軟件是在控制處理機(jī)CP中進(jìn)行組態(tài)和運行控制的，其中包括如下諸多模塊。 (1)ACCUM積算模塊：用于計算模擬型輸入信號(流量或脈沖數(shù))的累計值，可以串接起來使用。其中MTRFAC是輸入信號要轉(zhuǎn)換成輸出累計值時所需乘上的一個“倍率因子”，使得輸入信號的單位與輸出的積算值單位匹配。參數(shù)PCNTOP被組態(tài)為1時，模塊作為一個計數(shù)器，可積算輸入脈沖信號的脈沖數(shù)。 (2)AIN模擬信號輸入模塊：用于處理FBM的輸入信號，同時提供對輸入信號修正、濾波，輸出保持上次正常值，標(biāo)度輸出到所要求的工程單位，輸入通道故障報警，超量程及高/低值報警等功能。 (3)AINR冗余的模擬信號輸入模塊：用于處理來自冗余的模擬量輸入類型的現(xiàn)場總線I/O組件FBM的輸入信號，其他功能與AIN模塊相同。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.