SR620
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Catalog excerpts

Frequency Counters SR620 — Universal time interval and frequency counter SR620 Time Interval & Frequency Counter · 25 ps single-shot time resolution · 1.3 GHz frequency range · 11-digit frequency resolution (1 s) · 0.001° phase resolution · Statistical analysis & Allan variance · Graphical output to X-Y scopes · Hardcopy to printers and plotters · GPIB and RS-232 interfaces · Optional ovenized timebase The SR620 Time Interval Counter performs virtually all of the time and frequency measurements required in a laboratory or ATE environment. The instrument’s single-shot timing resolution and low jitter make it the counter of choice for almost any application. SR620 Measurements The SR620 measures time interval, frequency, pulse-width, rise and fall time, period, phase and events. Time intervals are measured with 25 ps rms resolution, making the SR620 one of the highest resolution counters available. Frequency is measured from 0.001 Hz to 1.3 GHz, and a choice of gates ranging from 1 period to 500 seconds is provided. The SR620 delivers up to 11 digits of frequency resolution in one second, making it suitable for measurement applications ranging from short-term phase locked loop jitter, to the long-term drift of atomic clocks. All measurement modes are supported by a wide variety of flexible arming and triggering options. Histograms and Strip Charts Unlike conventional counters that only have numeric displays, the SR620 provides live, graphical displays of measurement results. Graphical data is available in three formats: a histogram showing the distribution of values within a set of measurements, a strip chart of mean values from successive measurements, or a strip chart of jitter (standard deviation or Allan variance) values from successive measurements. Up to 250 strip-chart points or histogram bins can be displayed. Stanford Research Systems

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SR620 Time Interval & Frequency Counter Two DAC outputs continuously provide voltages proportional to the mean and the jitter of the measurement sample. These 0 to 10 V outputs can drive strip-chart recorders, or they can be set to provide fixed or scanned output voltages. Built-In Auto-Calibration A sophisticated, built-in auto-calibration routine nulls insertion delays between start and stop channels, and compensates for the differential nonlinearites inherent in analog timemeasurement circuitry. The auto-calibration routine takes about two minutes to perform, and should be run every 1000...

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Timebase Standard Option 01 Frequency 10.000 MHz 10.000 MHz Type TCVCXO Ovenized VCXO Aging 1 × 10–6/yr. 5 × 10–10/day Allan variance (1 s) 3 × 10–10 (typ.) <5 × 10–12 Stability (0 to 50 °C) 1 ppm <2 × 10–9 Settability 0.01 ppm 0.001 ppm External timebase User may supply 5 MHz or 10 MHz timebase (1 V nominal) Time Interval, Width, Rise and Fall Times Range –1000 s to +1000 s in ±TIME mode –1 ns to +1000 s in all others modes Trigger rate 0 to 100 MHz Display LSD 4 ps single sample, 1 ps with avg. Resolution Standard timebase (((25 ps typ. [50 ps max.])2 + (0.2 ppb × Interval)2) / N)1/2 rms...

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Input noise 350 µVrms (typ.) Prescaler see graph Protection 100 V, 50 Ω terminator is released if input exceeds ±5 Vp REF Output Frequency 1.00 kHz (accuracy same as timebase) Rise/fall time 2 ns Amplitude TTL: 0 to 4 V (2 V into 50 Ω) ECL: –1.8 to –0.8 V into 50 Ω DVM Inputs Full scale ±1.999 VDC or ±19.99 VDC Type Sample & hold with successive approximation converter Impedance 1 MΩ Accuracy 0.3 % of full scale Speed Approximately 5 ms Input sensitivity D/A Outputs Full scale ±10.00 VDC Resolution 5 mV Impedance <1 Ω Default Voltage proportional to mean and deviation Accuracy 0.3 % of full...

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