PDF《压力变送器常见问题分析》

BEIJING BRIGHTY INSTRUMENT CO.

,LTD. 压力变送器常见问题分析 Frequently Seen Problems &

Analysis of Pressure Transmitter 1. 加压变送器输出不变化,再加压变送器输出突然变化,泄压后变送器零位回不去. 产生此现象的原因有可能是压力传感器安装接口与使用设备螺纹连接的密封圈引起的, 一般是因为密封圈 规格的原因(太软或太厚) ,传感器拧紧时,密封圈被压缩到传感器引压口里面堵塞测压口,加压时压力介质 无法正常通过,当压力很大时突然冲开密封圈,压力传感器受到压力而变化,而压力再次降低时,密封圈又 回位堵住引压口,残存的压力释放不出,因此传感器零位又下不来.排除此原因的方法是将传感器正常卸下, 直接察看零位是否正常,如果正常请更换符合标准的密封圈再试. 压力变送器 常见问题分析 S・00 -2 3. 变送器通电无输出 可能的原因: A. 接错线错误或接线不牢固(包括地 线) (仪表和传感器都要检查) B. 导线本身断路或短路 C. 电源无输出或电源不匹配 D. 仪表损坏或仪表不匹配 E. 传感器损坏 1. Transmitter output doesn t change with a pressure applied, and then suddenly changes with more pressure applied, after relief of pressure, it doesn t return to zero. Possibly the problem arises from the transmitter s mounting connection and the utility equipment s threaded connection sealing ring, normally because of the specification of the sealing ring (too soft or too thick). When the transmitter is screwed in, the sealing ring is squeezed into the pressure guide hole and blocks it. When applying pressure, it can'

t enter in, when applying more pressure, the sealing ring is broken, the transmitter responds to the pressure variation, when the pressure goes down, the sealing ring block the pressure guide hole again, remaining pressure is trapped, so the it doesn t return to zero. The solution is to remove the transmitter by normal means to observe if zero is in proper condition, if so please replace with a sealing ring conforming to standard and try again. 2. 变送器输出信号不稳 可能的原因 A. 压力源本身是一个不稳定的压力 B. 仪表或压力传感器受到外界较强的干扰 C. 传感器接线不牢固 D. 传感器本身振动剧烈 E. 传感器的供电电压(24V.DC)不稳定 F. 传感器故障 G. 其他原因 2. Transmitter output is not stable Possibilities: A. Pressure source is not stable B. Gauge or transmitter is subject to high external interference C. Transmitter is not firmly wired D. Transmitter vibrates E. Power supply (24V.DC) is not stable F. Transmitter is faulty G. Others 3. No output while electrified Possibilities: A. Wrong wiring or unstable wiring (including earthing) (both gauge and transmitter should be checked.) B. Lead wire is open or short circuit C. No power output or power doesn t match D. Faulty gauge or gauge doesn t match E. Faulty transmitter 1-8 2007.9.10, 10:34 PM

2 S 北京布莱迪仪器仪表有限公司压力变送器 常见问题分析 S・00 -3 5. 压力上去,变送器输出上不去 1. 检查压力接口是否漏气或被堵;

2. 检查接线是否正确且接线可靠;

3. 检查供电电源是否可靠有效;

4. 检测变送器的零点是否有信号正常输 出,且加压时变送器的输出是否有同 比的变化;

5. 检查系统的连接后其他设备是否有问题 和损坏;

4. 变送器与指针式压力表对照偏差大 首先,出现偏差是正常的现象 其次,确认正常的偏差范围 确认正常误差范围的方法: 计算出压力表的误差值 例如:压力表量程为 30bar ,精度 1.5% ,最小刻度为 0.2bar 正常的误差为: 30bar*1.5%+ 0.2*0.5(视觉误差)=0. 55bar 压力变送器的误差值. 例如:压力传感器量程为 20bar ,精度 0.5% ,仪表精度为 0.2% , 正常的误差为:20bar*0.5%+20bar*0.2%=0.18bar 整体对照时出现的可能性误差范围应以大误差值的设备的误差范围为准,以上例来说,传感器与变送 器偏差值在 0.55bar 内可视为正常. 如果偏差非常大,应使用高精度仪表(至少此仪表精度应高于压力表和传感器精度)进行参照. 4. Big difference between transmitter and pointer type pressure gauge Firstly, it is normal to have difference Secondly, determine normal difference range Method to determine normal difference range Figure our error of pressure gauge For instance: range of pressure gauge is 30bar, accuracy 1.5%, minimum scale 0.2bar Normal error is: 30bar*1.5%+ 0.2*0.5 (parallex) =0. 55bar Error of Pressure Transmitter For instance: range of pressure sensor is 20bar, accuracy 0.5%, gauge accuracy is 0.2%, Normal error is: 20bar*0.5%+20bar*0.2%=0.18bar Possible error range coming from complete comparison should be the error of the equipment that produces bigger error, applying to above instance, the error of sensor and transmitter within 0.55bar should be regarded as normal. If difference is big, high accuracy gauge should be used (as least better accuracy than pressure gauge and sensor) for reference. 5. Pressure goes up, transmitter s output doesn t go up 1. check if pressure connection is leaking or blocked;

2. check if wiring is correct and well grounded;

3. check if power supply is reliable and effective;

4. check if transmitter outputs a signal at zero, and if output changes when pressurize;

5. check if other equipment after the system s connection are faulty;

1-8 2007.9.10, 10:34 PM

3 BEIJING BRIGHTY INSTRUMENT CO.,LTD. 压力变送器 常见问题分析 S・00 -2 6. 测量介质对于压力传感器的重要性 选择一个合适的压力传感器,了解介质的特点尤为重要. 1. 介质的腐蚀性如何,导电性如何.根据介质的这些属性选用相应类型的传感器. 2. 介质温度范围如何: 一是介质的经常性的温度范围为多少,根据此信息........