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我厂采用计算机控制合成氨工段整个生产过程。此工段共有138个检测点,其中压力16个、差压(阻力)12个、流量18个、液面18个、温度78个、成分6个。通过不同的变送器,把信号转变为:直流毫安信号、直流毫伏信号、电阻信号等。计算机模拟量输入部分的模数转换装置是把0～100mV 转换成0～1000个二进制数码,所以检测点送来的输入讯号应统一为0～100mV 的直流电压信号。根据我厂的具体情况是采用以下方法统一的。一、毫安(mA)输入:对生产过程中重要参数(流量、压力、差压、温度等)是采用变送器转换成0～10mA 讯号。让0～10mA 电流在10Ω精密电阻(0.1%)上流过,则可产生0～100mV 信号,
I plant a computer-controlled ammonia section of the entire production process. This section has a total of 138 test points, of which 16 pressure, pressure (resistance) 12, 18 flow, liquid level 18, temperature 78, the composition of six. Through different transmitters, the signal into: DC mA signal, DC millivolt signal, resistance signal. Analog to digital conversion part of the analog input device is 0 ~ 100mV converted into 0 to 1000 binary digital, so the detection point input signal should be unified into 0 ~ 100mV DC voltage signal. According to my factory’s specific situation is the use of the following method of unity. First, the milliampere (mA) input: The production process of important parameters (flow, pressure, differential pressure, temperature, etc.) is the use of the transmitter converts 0 ~ 10mA signal. Let 0 ~ 10mA current flow in 10Ω precision resistor (0.1%), can produce 0 ~ 100mV signal,