安規考慮：保護設備及人身安全，隔開潛在的高壓危險；
提高通信的穩定性：消除地電勢差的影響；
提高器件的可靠性：消除地環路影響；
低耦合：提高系統間的兼容性；
隔離接地的原理
總線增加隔離固然可以保證總線穩定可靠地通信，但是帶隔離通信接口的設備，在復雜的環境或安裝狀態下，接口會表現出完全不同的ESD特性，了解ESD對接口的影響機理，才能有針對性地增加保護器件，提升隔離接口的ESD能力。下面以帶有隔離CAN或RS-485通信接口為例，對常見的設備狀態下，ESD的作用機理進行分析，并提出相應的改善措施。
1、總線側懸空此狀態下，設備控制側有接入保護地（PE），總線側參考地懸空，與PE無任何連接，如下圖。
接下來進行分析：
假設控制側均做了足夠的保護措施，當控制側接口受到靜電放電時，能量通過控制側保護器泄放至PE，對隔離通信接口基本無影響，如下面左圖；
當總線接口受到靜電放電時，由于總線側懸空，能量只能通過隔離柵的等效電容Ciso進行泄放，由于Ciso非常小，僅有幾皮法至十幾皮法，Ciso被迅速充電，兩端電壓Viso會非常高，幾乎等同于放電電壓，電壓全部施加在隔離接口模塊的隔離柵，若電壓超出了隔離柵的電壓承受范圍，則會導致內部隔離柵損壞，如下面右圖。
注意：對于一般的隔離接口模塊，隔離柵可承受的靜電放電電壓只有4kV，對于更高等級的6kV或8kV的靜電來說是非常脆弱的，極易出現損壞情況。
2、設備控制測懸空此狀態下，設備控制側有接入保護地（PE），總線側參考地懸空，與PE無任何連接。此狀態下，設備控制側參考地懸空，與PE無任何連接，總線側有接入保護地（PE），如下圖。
接下來進行分析：
當總線側接口受到靜電放電時，靜電能量通過隔離接口模塊內部總線側器件泄放至PE，但若ESD能量超出了接口模塊內部總線側器件的ESD抗擾能力，總線接口則可能損壞，如下面左圖；
當控制側接口受到靜電放電時，由于控制側懸空，能量只能通過隔離柵的等效電容Ciso進行泄放，由于Ciso非常小，兩端電壓Viso會非常高，電壓全部施加在隔離接口模塊的隔離柵，若電壓超出了隔離柵的電壓承受范圍，則會導致內部隔離柵損壞，如下面右圖。
Siemens E550MA-W893-V-B
MI-T-M GC-1502-0ME1 COLD WATER PRESSURE WASHER 2 HP
COPELAND CRT5-0450-TFD-970/RUUD 55-22319-28S COMPRESSOR
BLACK BOX ACU2222A KVM EXTENDER 162988
CARRIER 16JB660028 ELECTRONIC CONTROL KIT 152619
LYON GRAY STORAGE CABINET-5 SHELVES 93589
US ELECTRIC BU48A 1 HP MOTOR 230/460 VOLT 855 RPM 81666
ELKAY PSDKAD2517VRC CLASSROOM DRINKING FOUNTAIN SINK
ELKAY ER101Y REMOTE WATER CHILLER 160634
CARRIER 5T2BGY22 STATOR 200HP 208/230V 60HZ 150178
MTI WRO7236E WHIRLPOOL TUB WITH PUMP 162321
WEATHERKING 90RS10EGS01278 94,500 BTU 92% GAS FURNACE
WINSMITH 926MDSN30DLR90-B1425 METRIC SPEED REDUCER 30:1
MTI QWODI6042 WHIRLPOOL OVAL TUB W/PUMP WHITE 162326
MTI QWODI6042 WHIRLPOOL OVAL TUB W/PUMP WHITE 162326
BLACK BOX SW843A#R2 SCSI SWITCH/REPEATER 147187
MAAX/AKER 141055-R-000 CORNER SHOWER 156704
DAYTON 15 HP INVERTER DUTY MOTOR 3 PHASE 159906
SIGHT SWITCH 16-PORT LB2016A# 153275
SIGHT SWITCH 16-PORT LB2016A# 153275
DAYTON 1/4 HP 18"FAN CIRCULATOR 115/230V 1725:RPM 90818
COMDIAL DX-80 7201 KSU1 KEY SERVICE UNIT 155129
MDU9700 NETLINK MDSL MODEM CHASSI 149309
WINSMITH 930 30:1 METRIC SPEED REDUCER 58 RPM 65369
BLACK BOX 665X305 100V TELEPHONE LINE SIMULATOR 153041
CENTURION HBBD-F036SA 3 TON SPLIT SYSTEM AC UNIT R22
DAYTON 48 inch AGRICULTURAL EXHAUST FAN 158441
DAYTON 48 Inch AGRICULTURAL EXHAUST FAN 158441
DAYTON 48inch AGRICULTURAL EXHAUST FAN 158441
HAIER HGV054N3H 54,000 90% UPFOW GAS FURNACE 46477
DANFOSS HCM094T4LC6 8 TON AC/HP SCROLL COMPRESSOR
SQUARE D SNC800LX CIRCUIT BREAKER ENCLOSURE 160917
VAPAC V8L3 SELF GENERATIVE STEAM HUMIDIFIER 165250
LEICA MICROSYSTEMS 14041260215 DISPLAY BLADE HOLDER
BLACK BOX TS624AE0305902 SCAN-LAN 80 CABLE SCANNER
VAPAC V4L2 SELF GENERATIVE STEAM HUMIDIFIER 165246
BERK-TEK ICP004CB3510/15-6090 PLENUM 6090' CABLE 143738
BLACK BOX EB-LH1110A S/A 1000 SX/MM-SC TO 155140
COPELAND ZPS51K4E-PFV-830/RUUD 55-23156-11S COMPRESSOR
CORNERING CABLE SYSTEMS EFN012A-0500 12 FIBER CABLE
RUBBERMAID 9T12 STANDARD PLATFORM TRUCK 146543
DELHI 218INS INLINE DUCT BLOWER WITHOUT MOTOR 35942
BLACK BOX EXP15006A-1000 FIBER OPTIC CABLE 1000' 156312
3M W344 AIRHAT POWER VENTILATED HELMET 159611
3M W344 AIRHAT POWER VENTILATED HELMET 159611
FRIEDRICH PDH15K5SD PTHP ELECTRIC 5 KW 159986
DAYTON 48" GRAVITY VENTLIATOR 32003
DAYTON 2N985G 7.5 HP ELECTRIC MOTOR 1770 RPM 95141
AL FLEX CHROME PROXIMITY ACCESS LOCK 153074
AL FLEX CHROME PROXIMITY ACCESS LOCK 153074
TRANE 4TEP3F63B1000AA 5T UP/HORIZONTAL FAN COIL 68354
DAYTON SLANTWALL 36" EXHAUST FAN 115/230 VOLT 152428
DAYTON 36" HEAVY DUTY EXHAUST FAN 46738
WINSMITH 935MWN15100-B METRIC SPEED REDUCER 15:1 67760
WINSMITH 935MWN30LR100-B5 SPEED REDUCER 30:1 89791
DAYTON 18 1/2" EXHAUST VENTILATOR 1/4-2 HP 158202
EMERSON CA35 10HP ELECTRIC MOTOR 230/460V 3 PHASE 80059
LG ELECTRONICS LSN092HE 9,800 BTU MINI-SPLIT HP FANCOIL
LG ELECTRONICS LSN092HE 9,800 BTU MINI-SPLIT HP FANCOIL
ADP FCMCC3260B202 5 TON UPFLOW FAN COIL WITH 20 KW HEAT
ALLIANCE SPR054A7RPZ 4.5T SCROLL AC/HP COMPRESSOR R-22
LUMAPRO MOBILE WORK LIGHT 120 VOLT 700 WATT 164981
DAYTON 20" NON-OSCILLATING AIR CIRCULATOR 159094
DAYTON 18" FAN CIRCULATOR 1/4 HP 3 PHASE 1750RPM 7982
KOHLER K-1193-LA-0 60"x42" WHITE FIBERGLASS BATH 160571
KOHLER K-1193-LA-0 60"x42" WHITE FIBERGLASS BATH 160571
DAYTON 3/4HP EXHAUST VENTILATOR 16-1/2" WHEEL DIA 13441
CLARKE W4260SKL-01CMH OCEANIA WHIRLPOOL SKIRTED TUB
CLARKE W4260SKR-01CMH OCEANIA WHIRLPOOL SKIRTED TUB
HALLOWELL URB3258-2ASB-PT ASSEMBLED LOCKER 159647
YORK K2EU060A06A 5 TON FAN COIL UNIT AC ONLY R22 140009
BLACK BOX ME0008A-MCAMP QUIKCONNECT MDSL LINE DRIVER
METRO 1848FS ADJUSTABLE SOLID SHELVING 48Wx18D 81477
FRIGIDAIRE FAM18ET2A WINDOW AIR CONDITIONER W/HEAT
DAYTON 30"VENTURI EXHAUST FAN/WALL MOUNTED 3/4HP 158216
GREENLEE RATCHETING REEL STAND/STEEL 159910
BLACK BOX IC508A FIBER OPTIC EXTENDER 162963
DAYTON C-FACE RIGHT ANGLE SPEED REDUCER 35329
THERMO SCIENTIFIC VACUUM CONTROLLER 0.01-20 TORR/110V
BLACK BOX TL572A 4 PORT BUFFER AMPERAGE: 16 162924
BLACK BOX ME552A-X21 CAMPUS FIBER DRIVER 147171
DAYTON 18" ROOF-TOP EXHAUST VENTILATOR 165115
EDSAL VC1505G SECURITY CABINET LOCKABLE HANDLE 145248
EAGLE ELECTRIC T3060SEB WORKTABLE 60Wx30Dx1 1/2H 147168
BLACK BOX EB-LRA1200A-1PS SINGLE AC-DC POWER CONVERTER
CARRIER 19DK111714 PURGE ASSEMBLY CHILLER/19DK-SERIES
COZY CF653C 65,000 DOWNFLOW GAS WALL FURNACE 16534
BRISTOL H26D44QBBCK 3 1/2TON TANDEM HERMETIC COMPRESSOR
OHAUS CH150R11-2E1 BENCH COUNTING SCALE 30614
DAYTON EXHAUST VENT 14 3/4" CENTRIFUGAL UPLAST 39474
SAINT GOBAIN PERFORMANCE PLASTICS AAA00078 CLEAR TUBING
DAYTON EXHAUST VENT 14 3/4 inch CENTRIFUGAL UPLAST
HALLOWELL USVP178816APT SAFETY VIEW LOCKER 161709
CD TOWERS FOR CD-ROM DISCS CDT300A-2-R7 153128
CD TOWERS FOR CD-ROM DISCS CDT300A-2-R7 153128
RHEEM ELD-30 30 GALLON ELECTRIC WATER HEATER 159022
MITSUBISHI PL18AK INDOOR AC FAN COIL UNIT 115V 47386
BLACK BOX LH8124A 24 PORT STACKABLE 10/100 144525
BLACK BOX CD227A-R4 OMNI TOWER W/ CD-ROM DRIVES 144940
CENTURY 6-349148-01 50 HP ELECTRIC MOTOR 4230
FUJI VFD41 2.2 HP REGENERATIVE BLOWER 230/460V 165185
EDSAL CSC6850 BLUE COMPUTER CABINET, LOCKABLE 145247
BLACK BOX IC946A# V.35 TO HSSI INTERFACE CONVERTER
METTLER TOLEDO MI-129 PORTABLE METER/ISFET PH 145850
COLD-WAVE MDR610A#33 153239
COLD-WAVE MDR610A#33 153239
ALLTECH AGILENT 122-1364 GAS CHROMATOGRAPHY COLUMN
FRIGIDAIRE FAS256N2A2 25,000 BTU WINDOW AIR CONDITIONER
FRIGIDAIRE FAS256N2A2 25,000 BTU WINDOW AIR CONDITIONER
TRANE GP34D-FG3-GA 3 TON AC/HP HERMETIC COMPRESSOR R22
SCOTT HEALTH & SAFETY 30 MIN LIGHTWEIGHT CYLINDER
6 ZONE 369 INDOOR TEMPERATURE CONTROL 148379
YORK P4DND20N10401 130,000 BTU 80% AFUE GAS FURNACE
YORK P3DND20N10401 130,000 BTU 80% AFUE GAS FURNACE
DAYTON TUBEAXIAL FAN 24"/6 BLADES 157681
YORK P4DND20N10401 130,000 btu 80% AFUE GAS FURNACE
DAYTON 24" EXHAUST FAN 1/2-1 HP 159197
INGERSOLL-RAND SB20C-ACS-A 2" SHOCK BLOCKER 146554
DAYTON 1/2 HP EXHAUST FAN CAPACITOR START 152075
SLOAN EAF150-ISM SENSOR ACTIVATED HAND WASHING FAUCET
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