A032-ET - International Laser Ranging Service

Event Timer A032-ET4.2. Measurement under variable gatingThis example demonstrates the speed abilities of online re-programming the gate delay. Ascompared to the previous example, in this case the output TEST OUT of the ET-deviceindicating the gate delay is connected via 3-m coaxial cable to the INPUT B (as Stop pulses) tomeasure and display the values of this delay under different measurement conditions.Setting the parameters for controlling the gate delay is shown inFig. C-8. This setting means that the control data will define thegate delay that first should rise from 200 to 500,00 ns with 10 nsincrement in each cycle and next fall down with the same speed.In fact we shall measure only initial (rising) part of these delays.The A032.2-C2 always restarts the measurement in response tothe every batch of data received from ET-server, and throughFig.C-8this action attempts to define a new gate delay value for eachnext measurement cycle. However the TCP/IP network mayproduce some unexpected delays for real-time data exchanging, resulting in troubles for suchinteractive operation at high rate of measurement cycle repetition. Specifically, in this case thecontrol data can be delivered later than the ET-server starts the corresponding cycle. What ismore, these data may consist of a few separate data blocks addressed to both the past cyclesand the current cycle. When the A032.2-C2 restarts the measurement, it takes into account onlythe latest data concerning the gate delay, omitting out-dated ones. In these cases some gaps inthe delay gate control appear.Fig. C-9 illustrates this effect forthe case of measurement at500 Hz cycle repetition rate. Ascan be seen, there are manyrepeated gaps in gate delaycontrol. Thus, the measurementunder variable gating athigh cycle repetition rate ispossible but with certainlimitations concerning the rateof gate delay modifying.When cycle repetition rate isnot so high, gapless onlinecontrol for gate delay is quitepossible. Fig. C-10 illustratessuch ability for 40 Hz cyclerepetition rate. In this casethere are no any gaps in delaycontrol.However in each specific case thehighest available rate of gaplesscontrol may depend on the variousthings, e.g., the actual performanceand charge of PC. It isrecommended to reproduce similarmeasure-ment under specificuser’s conditions with the aim toevaluate the actually availablemaximum rate of gapless gatedelay control.Fig.C-9Fig.C-1037