影响PLC控制系统的干扰源与一般影响工业控制设备的干扰源一样,大都产生在电流或电压剧烈变化的部位,这些电荷剧烈移动的部位就是噪声源,即干扰源。
干扰类型通常按干扰产生的原因、噪声干扰模式和噪声的波形性质的不同划分。其中:按噪声产生的原因不同,分为放电噪声、浪涌噪声、高频振荡噪声等;按噪声的波形、性质不同,分为持续噪声、偶发噪声等;按噪声干扰模式不同,分为共模干扰和差模干扰。共模干扰和差模干扰是一种比较常用的分类方法。共模干扰是信号对地的电位差,主要由电网串入、地电位差及空间电磁辐射在信号线上感应的共态(同方向)电压迭加所形成。共模电压有时较大,特别是采用隔离性能差的配电器供电室,变送器输出信号的共模电压普遍较高,有的可高达130V以上。共模电压通过不对称电路可转换成差模电压,直接影响测控信号,造成元器件损坏(这就是一些系统I/O模件损坏率较高的主要原因),这种共模干扰可为直流、亦可为交流。差模干扰是指作用于信号两极间的干扰电压,主要由空间电磁场在信号间耦合感应及由不平衡电路转换共模干扰所形成的电压,这种让直接叠加在信号上,直接影响测量与控制精度。
ASHCROFT 63-1008-A-02L-X?LJ-200#-BCF 0-200PSI PRESSURE GAUGE D553128
SI SPAN 23-0150-E1 0-100PSI PRESSURE GAUGE D578690
ASHCROFT PRESSURE GAUGE 0-60PSI 1/4 IN NPT D580305
ASHCROFT 50-300F THERMOMETER 1/2IN NPT D582823
ASHCROFT 100B-1 TEMPERATURE GAUGE 30-130F 1/2 IN NPT D580352
ASHCROFT 20W1005H02B 0-60PSI 2 IN 1/4 IN NPT PRESSURE GAUGE D564345
ASHCROFT 20W1005 H 02B VAC 0-30IN-HG 2 IN 1/4 IN NPT PRESSURE GAUGE D564347
ASHCROFT 20W1005 H 02B AGL 0-400KPA 0-60PSI PRESSURE GAUGE D564348
ASHCROFT PRESSURE GAUGE 0-160PSI 3-1/2IN 1/4IN NPT D583471
ASHCROFT PRESSURE GAUGE 30-0IN-HG 0-60PSI 1/4IN NPT D583473
AMETEK USG SOLFRUNT SILICONE FILLED PRESSURE GAUGE 0-400PSI 1/2 IN NPT D539735
AMETEK USG 0-30PSI 1/4 IN NPT PRESSURE GAUGE D539581
FOXBORO 0-450 3-15PSI 3-1/2 IN 1/4 IN NPT PRESSURE GAUGE D539681
NOSHOK 20-110-60 1/4IN NPT 0-60PSI PRESSURE GAUGE D587057
NOSHOK 20-110-60 1/8IN NPT 0-60PSI PRESSURE GAUGE D587059
WIKA PRESSURE GAUGE 0-2000PSI 1/4IN NPT D591072
ASHCROFT 20W1005 H 02B 0-15PSI 2 IN 1/4 IN NPT PRESSURE GAUGE D564788
WIKA 8945217 432.12.100 SEALGAUGE 0-250PSI 3/4 IN NPT PRESSURE GAUGE D564663
ASHCROFT 25W1005 H 02L 30#&VAC -30-0IN-HG 0-30PSI PRESSURE GAUGE D571399
AMETEK P781642 PRESSURE GAUGE 0-160PSI 2IN 1/4IN NPT D587280
ASHCROFT 63-1008-S-02B-3?0IMV&30#-XLJLL 30-0IN-HG 0-30PSI GAUGE D553883
3D INSTRUMENTS 2047-0185-22-M PRESSURE GAUGE 0-60PSI 4-1/2IN 1/4IN NPT D583366
WIKA 0-60PSI 2IN 1/4IN NPT PRESSURE GAUGE D572026
WIKA 111.10 0-100PSI 2 IN 1/4 IN NPT PRESSURE GAUGE D572050
WIKA B5 0-300PSI 1-3/4 IN 3/8 IN NPT PRESSURE GAUGE D572031
ASHCROFT 30-EI-60-R-060 BI-metaL THERMOMETER 0-250F 3IN 1/2IN NPT D583602
TRERICE B83106X08PI BI-metaL THERMOMETER 50-500F 10-260C 1/2IN NPT D583736
PTC 0.72 9 IN STEM THERMOMETER 50-500F D531557
MARSHALL TOWN 175-09-020 FIG 103 9 IN STEM THERMOMETER 40-140F D531569
MARSHALL TOWN 175-09-035 FIG 103 9 IN STEM THERMOMETER 50-500F D531549
ASHCROFT 20EI40R090 9 IN STEM BImetaL THERMOMETER 50-400F 2 IN D531561
USG 0-100PSI 1/4 IN NPT PRESSURE GAUGE D576547
MARSHALL TOWN 175-09-040 FIG 103 9 IN STEM THERMOMETER 60-220F D531556
USG 0-60PSI 4-1/2 IN 1/4 IN NPT PRESSURE GAUGE D576462
ASHCROFT 35-1009-SW-02L DURALIFE 0-400PSI 1/4IN NPT PRESSURE GAUGE D567913
FLAIR 1200053 STAINLESS 0-200PSI 1/4 IN NPT PRESSURE GAUGE D558255
VWR 89095-754 DIAL THERMOMETER 200MM PROBE 25-125F D551407
ASHCROFT 35-1009-AW-02L-?300 DURALIFE 0-300PSI 1/4IN NPT GAUGE D558277
TEMA 0-4BAR 1/2 IN NPT PRESSURE GAUGE D535858
WEISS 2 SUBD 0-250F 5 IN TEMPERATURE GAUGE D561793
WINTERS PRESSURE GAUGE 0-15PSI 2-1/2 IN 1/4 IN NPT D572499
MCDANIEL ConTROLS J60-0 PRESSURE GAUGE -60-0IN-WC 1/4 IN NPT D572457
REOTEMP MODEL A BImetaL THERMOMETER 4IN STEM 0-200F 3IN 1/2IN NPT D594921
H-B INSTRUMENT 9475 HOT WATER LINE THERMOMETER 40-260F 1/2 IN NPT D539817
AMETEK P500 U.S. GAUGE 0-100PSI 1/8 IN NPT PRESSURE GAUGE D562051
WIKA 111.10 4252978 0-300PSI 2 IN 1/4 IN NPT PRESSURE GAUGE D572180
WIKA 111.10 4252951 0-160PSI 2 IN 1/4 IN NPT PRESSURE GAUGE D572179
WIKA 212.53 4311957 0-200PSI 2 IN 1/4 IN NPT PRESSURE GAUGE D572177
ASHCROFT TRI-CLOVER 316 STAINLESS 0-100PSI PRESSURE GAUGE D572482
ASHCROFT DURALIFE PLUS 0-100PSI 3-1/2IN 1/4IN NPT PRESSURE GAUGE D586744
ASHCROFT DURALIFE 0-60PSI 1/4 IN NPT PRESSURE GAUGE D550185
WEKSLER EA14 0-300PSI 1/4IN NPT PRESSURE GAUGE D550210