Model 7002Switch System Instruction Manual - Advanced Test ...

Front Panel Operation4.17.2 Semi-synchronous operationIn the semi-synchronous Trigger Link mode all triggering(input and output) in the test system is controlled by a singleline. When the normally high (+5V) trigger line is pulled low(0V), a trigger occurs on the negative-going edge. When thetrigger line is released, a trigger occurs on the positive-goingedge (see Figure 4-29). The advantage of this single line triggeris that as long as one of the instruments in the systemholds the line low, the trigger is suppressed. In other words,the trigger will not occur until all instruments in the systemare ready.≈ +5V0VPulled Low byfirst InstrumentTrigger onNegative-goingEdgeTrigger onPositive-goingEdgeReleased bysecond InstrumentFigure 4-29Semi-synchronous trigger link pulse specificationsFor example, assume that a Model 2001 Multimeter is connectedto two Model 7002s for semi-synchronous operationas shown in Figure 4-30. All three instruments are programmedto use trigger line #1. The two Model 7002s haverelay settling times of 10msec and 50msec respectively.Assume that the 2001 initially performs a measurement. Afterthe reading is done, the meter will drive the trigger linelow. The negative-going edge will trigger both Model 7002sto close a channel. While the Model 7002s are in the processof closing a channel, they will hold the trigger line low. Tenmilliseconds after switch closure, the first Model 7002 willrelease the trigger line. However, the second Model 7002will continue to hold the line low since it is not finished. Fiftymilliseconds after switch closure, the second Model 7002will release the trigger line. The positive-going edge willtrigger the meter to perform a measurement and subsequentlypull the trigger line back down to close the next channels.This process continues until all channels are scanned andmeasured.Semi-synchronous trigger link exampleThis example uses the same test system (Figure 4-22) thatwas used for the asynchronous Trigger Link example #1.However, triggering will be done using the semi-synchronousmode. Trigger Link connections are shown in Figure4-31.Trigger LinkCables (2)(8501)INININOUTTriggerLink2001 MultimeterLine #17002 Switch SystemOUTTriggerLinkLine #17002 Switch SystemOUTTriggerLinkFigure 4-30Typical semi-synchronous mode connections4-68