A032-ET - International Laser Ranging Service

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Event Timer A032-ET2. Main features of the Event Timer2.1. ArchitectureLike most of the virtual instruments, the A032-ET performs its measurement functions partly byhardware means and partly by software means. The measurement software provides interfacingwith a user program via TCP/IP network on the basis of well-known “Client/Server” scheme(Fig.1). The user program can control the A032-ET via this interface and receive measurementdata from for further specific-application processing. This is not quite the usual way ascompared to another ways of connecting devices to user’s PC (such as parallel ports, serialports and USB). However the network connection offers capacities that are inaccessible for themost of conventional connections, especially in the case of designing distributed timingsystems. At the same time the network interface based on TCP/IP standards is quite get-at-ablefor users as almost all Software Development Kits contain the library with the required TCPfunctions.In terms of the Client/Server architecture theA032-ET can be considered as combination ofa specialised timing device (subsequentlyreferred to as ET-device), and a specialisedServer (subsequently referred to as ET-server)dedicated both to managing the ET-device andprocessing the timing data obtained from it(Fig.1). In this case the ET-client is a PC onwhich user runs his application, using thespecific ET-server resources via network. Notethat in many cases a single PC under MS-Windows can serve as both the ET-server andthe ET-client although use of a separate PC forthe ET-server is preferable to achieve thehighest operating speed.ET-deviceMeasurementsoftwareNetwork connectionFig.1. Network architecture of the Event TimerThe ET-device is compatible with different options of the ET-server software, providing differentmodes of the timer operation. Currently two kinds of ET-server software are available,specifying the option (either A032.1 or A032.2) of the Event Timer A032-ET as a whole. Any ofthese options can be used alternatively depending on the current user task.Event Timer A032-ETET-serverInputsTCP/IPPCInteraction via EPPTCP/IPPCUser programET-client2.2. Principles of operationThe A032-ET performs the measurement of input events in two stages. At first, the ET-devicetransforms every input event into single 80-bit timing data block (subsequently referred to asTD-block) and sequentially accumulates such TD-blocks in a buffer FIFO memory. Each TDblockcontains the rough data (39 bits) and interpolating data (40 bits) about the time of eventincoming, as well as one-bit mark specifying the input (either A or B) providing the measuredevent. Note that the interpolating data are presented initially in an intermediate redundant formand needs further an additional processing by the ET-server.The used unconventional method of time interpolation supports both high precision and highspeed. Specifically, using 100 MHz internal clocks it provides each single measurement with
Event Timer A032-ETAt the next stage the ET-server takes out TD-blocks from the FIFO memory and processesthem to obtain the corresponding time-tags in a unified form. Further these time-tags are sent tothe ET-client via network. To achieve the best precision, processing of TD-block takes intoaccount the actual physical characteristics of time interpolation under actual operatingconditions of the ET-device; these characteristics are defined through so called scaling(calibration) procedure before the measurement.The ET-device is flexibly controllable and, in particular, allows writing TD-blocks in the FIFOmemory and reading of them by the ET-server in different modes depending on the event timeroption:The A032.1 option provides continuous (gapless) event measurement during practicallyunlimited time. To do that, the ET-device continuously accumulates TD-blocks in FIFOmemory in order of measured event incoming. Concurrently with this process, the ETservercontinuously monitors the current state of the FIFO memory with some userdefinedperiod T M to detect the state when the amount M of TD-blocks exceeds the userselectablevalue (204, 102, 50, or 25 TD-blocks). The rest of the FIFO memory capacity isused to damp possible bursts of input event intensity.When the specified FIFO state is detected, the ET-server takes out M TD-blocks from theET-device, processes them and sends the corresponding time-tags to the ET-client(Fig.2). Such procedure is being cyclically repeated. In this way continuous eventregistration goes together with cyclical timing data processing and sending the time-tagsto the ET-client via TCP interface.TD-blocksMFIFO fillingFIFOmonitoringDatareadingT MDataprocessingand sendingTo TCPTo TCPTo TCPTo TCPTo TCPFig.2. Schematic time diagram, illustrating process of data reading from the ET-deviceThe maximum available mean rate of such continuous measurement is limited mainly bythe available reading and processing speed of the TD-block by PC of the ET-server.Typically (although it may depend on the actual performance of the PC) the total time ofreading and processing of the single TD-block is about 0.1 ms, resulting in maximummean measurement rate about 10 KHz.In any specific application the monitoring period T M and the amount M of TD-blocks canbe adapted to the expected mean rate R of event measurement to avoid FIFO memoryoverflow. Generally the period T M has to be defined so that it is a little less than the meantime M/R of accumulating M TD-blocks in the FIFO memory in view of the rate R. Forexample, if R=10 KHz and M=204, the period T M should be less than the timeM/R=20.4 ms. The minimum allowable value of T M is 10 ms.Note that the values M=204 and T M =15-20 ms are applicable for any rate R
Page 1 and 2: Event Timer A032-ETManualInstitute
Page 3 and 4: Event Timer A032-ETCONTENTSNotices
Page 5: Event Timer A032-ETSummary of speci
Page 9 and 10: Event Timer A032-ETGenerally the A0
Page 11 and 12: Event Timer A032-ET- Time synchroni
Page 13 and 14: Event Timer A032-ET“Measurement
Page 15 and 16: Event Timer A032-ETThe ET-device do
Page 17 and 18: Event Timer A032-ETInteraction proc
Page 19 and 20: Event Timer A032-ET* Normally delay
Page 21 and 22: Event Timer A032-ET2.6. Measurement
Page 23 and 24: Event Timer A032-ETpar5 - waiting p
Page 25 and 26: Event Timer A032-ETDEMO subsystem A
Page 27 and 28: Event Timer A032-ET3.1. Accessory p
Page 29 and 30: Event Timer A032-ETZoomOut - click
Page 31 and 32: Event Timer A032-ETDEMO subsystem A
Page 33 and 34: Event Timer A032-ET3.1. Accessory p
Page 35 and 36: Event Timer A032-ET“Graph” - ri
Page 37: Event Timer A032-ET4.2. Measurement

A032-ET - International Laser Ranging Service

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