Product Overview

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 Hardcopy to printers and plotters GPIB and RS-232 interfaces Optional ovenized timebase Features and Specifications: 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. 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 are provided. The SR620 delivers up to 11 digits of frequency resolution in a 1 second measurement. It's suitable for measurement applications ranging from short-term phase locked loop jitter, to long-term drift of atomic clocks. All measurement modes are supported by a wide variety of flexible arming and triggering options. Histograms & Strip Charts: Unlike conventional counters that only have numeric displays, the SR620 Frequency Counter 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. Both histograms and strip charts can be displayed on any oscilloscope with an X-axis input (see the pictures above), or can be plotted on an HP-GL compatible plotter or dot-matrix printer. Convenient cursors allow you to read the value of any data point in the histogram or strip chart. Autoscale and zoom features make it simple to display all, or any portion, of the graphs. Specifications 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 or 10 MHz timebase. 1 volt nominal. Time Interval, Width, Rise and Fall Times Range -1000 to +1000 s in +/-TIME mode; -1 ns to +1000 s in all other modes Trigger rate 0 to 100 MHz Display LSD 4 ps single sample, 1 ps with averaging Resolution        Standard timebase (((25 ps typ. [50 ps max.])2 + (0.2 ppb × Interval)2) / N)1/2 rms      Option 01 (((25 ps typ. [50 ps max.])2 + (0.05 ppb × Interval)2) / N)1/2 rms, (N = sample size) Error <±(500 ps typ. [1 ns max.] + Timebase Error ×Interval + Trigger Error) Relative error <±(50 ps typ. [100 ps max.] + Timebase Error x Interval) Arming modes +TIME (Stop is armed by Start) +TIME EXT (Ext arms Start) +TIME EXT HOFF (Leading EXT edge arms Start, trailing EXT edge arms Stop) ±TIME (Armed by Start/Stop pair) ±TIME CMPL (Armed by Stop/Start pair) ±TIME EXT (Armed by EXT input edge) EXT arming may be internally delayed or scanned with respect to the EXT input in variable steps. The step size may be set in a 1-2-5 sequence from 1 µs to 10 ms. The maximum delay is 50,000 steps. Display 16-digit fixed point with 1 ps LSD Sample rate N ×(800 µs + measured time interval) + calculation time (N=sample size) The calculation time occurs only after N measurements are completed and varies from zero (N=1, no graphics, binary) to 5 ms (N=1, no graphics) to 10 ms (display mean or standard deviation) to 60 ms (histogram). Frequency Range 0.001 Hz to 300 MHz via comparator inputs. 40 MHz to 1.3 GHz via internal UHF prescalers. RATIO A/B range: 10-9 to 103 Error <±((100 ps typ. [350 ps max.])/Gate + Timebase Error ) × Frequency Gates External, 1 period, 1 µs to 500 s in 1-2-5 sequence. Gates may be externally triggered with no delay. Gates may be delayed relative to an EXT trigger. The delay from trigger is set from 1 to 50,000 gate widths. Display 16-digit fixed point with LSD = Freq × 4 ps/Gate. 1 µHz maximum resolution (1 nHz with ×1000 for frequencies <1 MHz) Period Range 0 to 1000 s RATIO A/B range: 10-9 to 103 Error <±((100 ps typ [350 ps max])/Gate + Timebase Error) × Period Gates Same as frequency Display 16-digit fixed point with LSD = 1 ps (1 fs with ×1000 for periods <1 s) Phase Definition Phase = 360 × (Tb - Ta) / Period A Range -180 to +180 degrees, 0 to 100 MHz Resolution (25 ps × Freq. × 360 + 0.001)° Gate 0.01 seconds (1 period min.) for period measurement and 1 sample for time interval measurement. Period may also be measured using externally triggered internal gates as in frequency mode. Error <±(1 ns × Freq. × 360 + 0.001)° Counts Range 1012, RATIO A/B range: 10-9 to 103 Count Rate 0 to 300 MHz Gates Same as frequency Display 12 digits Inputs Bandwidth 300 MHz, 1.2 ns rise time Threshold -5.00 to +5.00 VDC (10 mV resolution) Accuracy 15 mV + 0.5 % of setting Sensitivity See graph      Auto level Threshold set between peak input excursions. (f >10 Hz, duty cycle >10-6) Slope Rising or falling edge Impedance (1 MΩ + 30 pf) or 50 Ω 50 Ω termination has SWR < 2.5:1 from 0 to 1.3 GHz Coupling AC or DC (Ext is always DC coupled) 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 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 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 scale Graphics Scope Two rear-panel outputs to drive x-y analog oscilloscope Displays Histograms and strip charts of mean and jitter X-axis -5 V to +5 V for 10 division deflection Y-axis -4 V to +4 V for 8 division deflection Resolution 250 (H) × 200 (V) pixels Hardcopy Centronics port for dot matrix printers. RS-232, IEEE-488.2 for HP-GL compatible plotters. Interfaces RS-232C 300 baud to 19.2 kbaud. All instrument functions may be controlled. GPIB IEEE-488.2 interface. All instrument functions may be controlled. Speed Approximately 150 ASCII formatted responses per second. 1400 binary responses per second. General Operating 0 °C to 50 °C Power 70 W, 100/120/220/240 VAC (+5 %, -10 %), 50/60 Hz Dimensions 14" × 3.5" × 14" (WHL)