Stanford Research Systems, Inc. (SRS) Time Interval / Frequency Counter

The SR620 Time Interval Counter performs virtually all ofthe time and frequency measurements required in a laboratory or ATEenvironment. The instrument's single-shot timing resolution and low jitter makeit the counter of choice for almost any application. · 25 ps single-shot time resolution · 1.3 GHz frequency range · 11-digit frequency resolution (1 s) · Statistical analysis & Allan variance · Graphical output to XY scopes · GPIB and RS-232 interfaces ·  Ovenized timebase(opt.) SR620 Measurements The SR620 measures timeinterval, frequency, pulse-width, rise and fall time, period, phase and events.Time intervals are measured with 25 ps rms resolution, making the SR620 one ofthe highest resolution counters available. Frequency is measured from 0.001 Hzto 1.3 GHz, and a choice of gates ranging from 1 period to 500 seconds isprovided. The SR620 delivers up to 11 digits of frequency resolution in onesecond, making it suitable for measurement applications ranging from short-termphase locked loop jitter, to the long-term drift of atomic clocks. Allmeasurement modes are supported by a wide variety of flexible arming andtriggering options. Histograms and StripCharts Unlike conventionalcounters that only have numeric displays, the SR620 provides live, graphicaldisplays of measurement results. Graphical data is available in three formats:a histogram showing the distribution of values within a set of measurements, astrip chart of mean values from successive measurements, or a strip-chart ofjitter (standard deviation or Allan variance) values from successivemeasuremen ts. Up to 250 strip-chart points, or histogram bins, can bedisplayed. Both histograms andstrip charts can be displayed on any oscilloscope with an X-axis input (seepictures), or can be plotted on an HP-GL compatible plotter or dot-matrixprinter. Convenient cursors allow you to read the value of any data point inthe histogram or strip chart. Autoscale and zoom features make it simple todisplay all, or any portion, of the graphs. Complete StatisticalCalculati ons The SR620 can makemeasurements on a single-shot basis, or calculate the statistics of a set ofmeasurements. Sample sizes from one to one million can be selected. The SR620will automatically calculate the mean, standard deviation or Allan variance,minimum and maximum for each set of measurements. Reference Output A precision 50 % dutycycle square wave (1 kHz) is available at the front-panel REF output. The REFoutput can be used as a source of start or stop pulses for any of the SR620'smeasurement modes. For instance, the length of a cable connected between REF andthe B input can be precisely determined by measuring the time delay between REFand B. Built-In DVMs andAnalog Outputs Two rear-panel DVMinputs make measurements of DC voltages with 0.3 % accuracy (±20 VDC range).These values may be read via the interfaces or displayed directly on the frontpanel. Two DAC outputscontinuously provide voltages proportional to the mean and the jitter of themeasurement sample. These 0 to 10 V outputs can drive strip chart recorders, orthey can be set to provide fixed or scanned output voltages. Built-InAuto-Calibra tion A sophisticated,built- in auto-calibration routine nulls insertion delays between start and stopchannels, and compensates for the differential nonlinearites inherent in analogtime-measureme nt circuitry. The auto-calibration routine takes about twominutes to perform, and should be run every 1000 hours of operation. 10 MHz Reference The choice of timebaseaffects both the resolution and accuracy of measurements made with the SR620.SRS offers a choice of a standard timebase with an aging coefficient of 1 × 10-6/year, or an optional ovenized-oscillator timebase with only 5 ×10-10/day aging, and about an order of magnitudebetter short-term stability than the standard timebase. A rear-panel input letsyou connect any external 5 MHz or 10 MHz source as a timebase. Computer Interfaces Standard GPIB(IEEE-488.2) and RS-232 interfaces allow remote control of the SR620. Allinstrument functions and configuration menu settings are accessible via theinterfaces. A fast binary dump mode outputs up to 1400 measurements per secondto a computer. A parallel printer port allows direct printing from theinstrument. Standard IEEE-488.2 communications are supported, and plotteroutputs are provided in HP-GL format. For convenient debugging, the last 256characters transmitted over the interfaces can be viewed on the front panel.