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在化工生产中,一般都采用差压变送器来测量气体压力与液体液位的变化量。但对微弱的气压差信号,就不能简单用微差压变送器来直接测量。尤其对几毫米至十几毫米水柱脉动信号的测量,引起的误差很大甚至会出现负值。下面举例说明。图1为10mm H_2O微差压变送器测量风管两端压降的示意图。实际风压降为0～5 mm H_2O。从图中可知P_1>P_2风管两端压降ΔP_(12)>0,变送器的输出信号也为正值。但是在风机开动时,差压变送器输出突然变负,过几十秒钟后才指示正常;停车时输出最大。其原因如下:
In chemical production, differential pressure transmitters are generally used to measure changes in gas pressure and liquid level. But for the weak pressure difference signal, you can not simply use the differential pressure transmitter to measure directly. Especially for a few millimeters to ten millimeters of water column pulse measurement, the error caused by a large or even negative. Here’s an example. Figure 1 is a schematic diagram of the pressure drop across the duct of a 10 mm H_2O differential pressure transducer. The actual pressure drop is 0 ~ 5 mm H_2O. It can be seen from the figure P_1> P_2 duct pressure drop across the duct ΔP_ (12)> 0, the transmitter output signal is also positive. However, when the fan starts, the differential pressure transmitter output suddenly becomes negative, after a few seconds to indicate normal; maximum output when parking. The reason is as follows: