HONEYWELL 51204126-915在網(wǎng)絡(luò)層生成并發(fā)送主時(shí)鐘對(duì)時(shí)報(bào)文,每隔10s向電廠總線發(fā)送一次。RTT發(fā)送時(shí)間報(bào)文zui多等待1ms。如在1ms之內(nèi)無法將報(bào)文發(fā)到總線上,則取消本次時(shí)間報(bào)文的發(fā)送:如報(bào)文發(fā)送過程被中斷,則立即生成一個(gè)當(dāng)前時(shí)間的報(bào)文。時(shí)鐘報(bào)文具有一個(gè)多播地址和特殊幀頭,日期為從1984.01.01至當(dāng)天的天數(shù),時(shí)間為從當(dāng)天00:00:00,000h至當(dāng)前的ms值,分辨率為10ms。
HONEYWELL 51204126-915從電廠總線上獲取時(shí)間報(bào)文。在OM650內(nèi),使用Unix功能將時(shí)間傳送給終端總線上的SU、OT等。通常由一個(gè)PU作為時(shí)間服務(wù)器,其他OM650設(shè)備登錄為是境客戶。
HONEYWELL 51204126-915的AP在啟動(dòng)后,通過調(diào)用“同步”功能塊,自動(dòng)與CP1430實(shí)現(xiàn)時(shí)鐘同步。然后CP1430每隔6s與AP對(duì)時(shí)。
TXP時(shí)鐘的精度如下:
從上述TXP時(shí)鐘同步方式及時(shí)鐘精度可以看出,TXP系統(tǒng)內(nèi)各進(jìn)鐘采用的是主從分級(jí)同步方式,即下級(jí)時(shí)鐘與上級(jí)時(shí)鐘同步,越是上一級(jí)的時(shí)鐘其精度越高。
三、GPS同步時(shí)鐘系統(tǒng)及時(shí)鐘同步誤差
3.1 HONEYWELL 51204126-915時(shí)鐘誤差
*,計(jì)算機(jī)的時(shí)鐘一般都采用石英晶體振蕩器。晶振體連續(xù)產(chǎn)生一定頻率的時(shí)鐘脈沖,計(jì)數(shù)器則對(duì)這些脈沖進(jìn)行累計(jì)得到時(shí)間值。由于時(shí)鐘振蕩器的脈沖受環(huán)境溫度、勻載電容、激勵(lì)電平以及晶體老化等多種不穩(wěn)定性因素的影響,故時(shí)鐘本身不可避免地存在著誤差。
例如,某精度為±20ppm的時(shí)鐘,其每小時(shí)的誤差為:(1×60×60×1000ms)×(20/10.6)=72ms,一天的累計(jì)誤差可達(dá)1.73s;若其工作的環(huán)境溫度從額定25℃變?yōu)?5℃,則還會(huì)增加±25ppm的額外誤差。可見,DCS中的時(shí)鐘若不經(jīng)定期同步校準(zhǔn),其自由運(yùn)行一段時(shí)間后的誤差可達(dá)到系統(tǒng)應(yīng)用所無法忍受的程度。
隨著晶振制造技術(shù)的發(fā)展,目前在要求高精度時(shí)鐘的應(yīng)用中,已有各種高穩(wěn)定性晶振體可供選用,如TCXO(溫度補(bǔ)償晶振)、VCXO(壓控晶振)、OCXO(恒溫晶振)等。
3.2 GPS同步時(shí)鐘系統(tǒng)同步誤差
如果對(duì)類似于TXP的時(shí)鐘同步方式進(jìn)行分析,不難發(fā)現(xiàn)時(shí)鐘在自上而下的同步過程中產(chǎn)生的DCS的對(duì)時(shí)誤差可由以下三部分組成:
3.2.1 GPS同步時(shí)鐘與衛(wèi)星發(fā)射的UTC(世界協(xié)調(diào)時(shí))的誤差
HONEYWELL 51204126-915這部分的誤差由GPS同步時(shí)鐘的精度所決定。對(duì)1PPS輸出,以脈沖前沿為準(zhǔn)時(shí)沿,精度一般在幾十ns至1μs之間;對(duì)IRIG-B碼和RS-232串行輸出,如以中科院國(guó)家授時(shí)中心的地鐘產(chǎn)品為例,其同步精度以參考碼元前沿或起始相對(duì)于1PPS前沿的偏差計(jì),分別達(dá)0.3μs和0.2ms。
Brook Crompton Betts AE180M3 EW579057 3 phase flame proof motor 18.8kW 33A 415V
ValuScan 6500Series 600mm LIGHT CURTAIN PAIR Machine Guarding
Nadex Phase 5 SCR spot weld welding controller contactor PH5 nadesco
100 Tonne Hydraulic Jack Lifting Ram Steeger Engineeering HCS 100T 50 SAL 427
Rosemount Alphaline Pressure transmitt 1151DP4S22B2M1I?7
APC D2A43016 channel D to A converter 0-20ma outputs
Elliott Steam Turbine Thrust Bearing P1562G711
Temporary 3 Phase Power distribution board 9 x GPO External Switch
SMC Seon-Il 5" 5inch bolted bonnet globe valve Class 300P flanged WCB / CR13
Pope 13KW 2 pole 2920RPM 3 phase induction motor
EastWest Engineering crane lift GB-CM2 Gas Cylinder Bottle Storage Cage stillage
PLC vacuum transfer system in cabinet 600 x 600 x 200
Harris 4 way oxy acetylene gas 8 x Regulator portable manifold cut weld heat
Rosemount 8800 W010SA1N1D117M1 Vortex Flowmeter Flow Meter Tube 1" inch
CEM Vibratory Bowl Feeder & Associated Equipment Type C-50
Cooling Tower Chemical Fluid Systems CTC-2 dosing system & 3 peristaltic pump
East West Engineering NWB-T1 fork lift bin tipping attachment
12 Way Pneumatic Manifold suit process valve control
SEW Movitrac LT P MCLTPA00755A340?0 7,5 KW 10hp soft starter
Knight Air Balancer KBC200-110 90kg @ 100 PSI capacity air balancer
Motor Start & Control Meter Panel Autotransformer Resistance ex TAFE Training
Speakman Emergency industrial safety shower eye wash water filter housing
Speakman Emergency industrial safety shower eye wash decontamination station
ABB Bailey & Fischer Signal Converter MAG-XM Model 50XM2000 Mag flow meter