Time Interval and Frequency Counter

32 Programming Commandssynchronizing of the measurements with thereturned answers.DREL (?) jThe DREL command sets the display rel and isequivalent to the front panel "SET REL" button.The parameter j = 1 sets the REL, j = 0 clears theREL, and j = 2 clears the REL and the results ofthe last measurement, j =3 sets the REL to thecurrent cursor position.COMPThe COMP command changes the arming parityin ± time arming mode. This command is the sameas toggling the state of the front panel COMPLLED.GATE (?) xThe GATE command sets the width of thefrequency, period, or count gate to x. The gatewidth x may range from 1ms to 500s in a 1,2,5sequence. If the value x is negative the gate is setto an externally triggered gate of width x. If themeasurement mode or arming mode do notsupport gates an error occurs.JTTR (?) jThe JTTR command sets the type of jittercalculation. The parameter j = 0 sets standarddeviation calculation while j = 1 sets Allanvariance. It should be noted that the jitter type is aproperty of the present mode and that if the modeis changed the jitter type may also change.MODE (?) jThe MODE command sets the instrumentmeasurement mode according to the followingtable:jmode0 time1 width2 rise/fall time3 frequency4 period5 phase6 countNote: after setting the SR620's mode the othermeasurement parameters should be set to theirdesired values because changing modes maycause them to change.SIZE (?) xThe SIZE command sets the number of samplesin a measurement. The parameter x may bebetween 1 and 10^6 in a 1,2,5 sequence. TheSIZE? query returns a floating point number withone significant digit.SRCE (?) jThe SRCE command sets the source of themeasurement. The parameter j = 0 set the sourceto A, j = 1 sets the source to B, and j = 2 sets thesource to REF. Additionally, in frequency, period,and count modes j = 3 sets the source to ratio(A/B). In phase mode the source is fixed and maynot be set while in rise/fall time REF may not beselected as the source.STRTThe STRT command is equivalent to pushing thefront panel START button.STOPThe STOP command resets the presentmeasurement and is the same as pressing the"RESET" button on the front panel.Data Transmission CommandsMEAS? jThe MEAS? query starts a measurement andreturns the result when the measurement iscomplete. The parameter j selects which statisticis to be returned.jstatistic0 mean1 jitter2 max3 minThis command always returns the value of thenext complete measurement. Thus, if ameasurement is in progress the command willreturn the value of the present measurement whenit is done, not a new measurement. It isrecommended that automeasure be off whenusing this command to ensure that the resultSR620 Universal Time Interval Counter