this one has option 1 the ultra stable accurate timebase which is a must if youre not going to use an external reference. the stock ones are not very stable I also have one without the opt 1 for 300$ less if you already have an external rubidium source. This unit is fully calibrated and comes with a calibration certificate and sticker . calibrated by the internal cal and the timebase 10 mhz accuracy manual adjustment . guaranteed to perform well within specs or your money back! this is a great unit. I used it to calibrate some generators. I get them in all the time so no need to keep this one. Tested perfect. I ran the self cal after 30 minutes and it passes perfectly. it passes startup tests every time too out of 10 startups. all knobs and inputs/outputs/leds work like new. guaranteed to work perfect within 7 days or your money back no problem. . you dont need to send these for cal ever because of the internal cal. its just a few buttons and then its as good as new again! this is a late model 2147 serial 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 SR620 Front Panel SR620 Rear Panel 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 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. Allan Variance Plot Histogram Display Histograms and 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. Complete Statistical Calculations The SR620 Time Interval / Frequency Counter can make measurements on a single-shot basis, or calculate the statistics of a set of measurements. Sample sizes from one to one million can be selected. The SR620 will automatically calculate the mean, standard deviation or Allan variance, minimum and maximum for each set of measurements. Reference Output A precision 50 % duty cycle square wave (1 kHz) is available at the front-panel REF output. The REF output can be used as a source of start or stop pulses for any of the SR620's measurement modes. For instance, the length of a cable connected between REF and the B input can be precisely determined by measuring the time delay between REF and B. Built-In DVMs and Analog Outputs Two rear-panel DVM inputs 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 front panel. Two rear-panel 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 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 time-measurement circuitry. The auto-calibration routine takes about two minutes to perform, and should be run every 1000 hours of operation. 10 MHz Reference The choice of timebase affects 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 x 10-6/year, or an optional ovenized-oscillator timebase with only 5 x 10-10/day aging, and about an order of magnitude better short-term stability than the standard timebase. A rear-panel input lets you 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 Frequency Counter. All instrument functions and configuration menu settings are accessible via the interfaces. A fast binary dump mode outputs up to 1400 measurements per second to a computer. A parallel printer port allows direct printing from the instrument. Standard IEEE-488.2 communications are supported, and plotter outputs are provided in HP-GL format. For convenient debugging, the last 256 characters transmitted over the interfaces can be viewed on the front panel. *Related Products* CG635 Synthesized Clock Generator FS725 Benchtop Rubidium Frequency Standard SIM940 Rubidium Frequency Standard SR625 Frequency Counter with Rb Timebase Specifications Timebase Standard Option 01 Frequency 10.000 MHz 10.000 MHz Type TCVCXO Ovenized VCXO Aging 1 x 10-6/yr 5 x 10-10/day Allan variance (1 s) 3 x 10-10 (typ.) <5 x 10-12 Stability 0 to 50 °C 1 ppm <2 x 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 x Interval)2) / N)1/2 rms Option 01 (((25 ps typ. [50 ps max.])2 + (0.05 ppb x Interval)2) / N)1/2 rms, (N = sample size) Error <±(500 ps typ. [1 ns max.] + Timebase Error xInterval + 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 x(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 ) x 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 x 4 ps/Gate. 1 µHz maximum resolution (1 nHz with x1000 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) x Period Gates Same as frequency Display 16-digit fixed point with LSD = 1 ps (1 fs with x1000 for periods <1 s) Phase Definition Phase = 360 x (Tb - Ta) / Period A Range -180 to +180 degrees, 0 to 100 MHz Resolution (25 ps x Freq. x 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 x Freq. x 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 M? + 30 pf) or 50 ? 50 ? 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 ? 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 ?) ECL: -1.8 to -0.8 V into 50 ? DVM Inputs Full scale ±1.999 VDC or ±19.99 VDC Type Sample & hold with successive approximation converter Impedance 1 M? Accuracy 0.3 % of full scale Speed Approximately 5 ms D/A Outputs Full scale ±10.00 VDC Resolution 5 mV Impedance <1 ? 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) x 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" x 3.5" x 14" (WHL) Weight 11 lbs. I accept Paypal ( I prefer E-check funding if possible, Contact me for information on e-check funding thru paypal) IF YOU HAVE ANY QUESTIONS AT ALL FEEL FREE TO CONTACT ME (I AM VERY FLEXIBLE AND EASY TO WORK WITH : INCLUDING SHIP-TO ADDRESSES , BUY IT NOW PRICES ,FREE EXTRA ITEMS INCLUDED ,etc...) Read my 100 Percent Positive FEEDBACK! My feedback says it all! I may be willing to reduce the buy it now price if you are a serious buyer. Just message me. For information on how you are protected as a buyer for my auctions go to this site: http://pages.ebay.com/help/buy/protection-programs.html For test equipment I am the largest used Stanford Research Systems dealer in the world. I am also known for my HP / Agilent spectrum analyzer and function generator sales as well. For test equipment I am very knowledgeable with SRS and HP agilent equipment : pricing , testing,reconditioning, and fixing basic issues. Every price that is listed is a price that the same unit sold for before at least a few times. I am not like the other dealers who list for rediculous prices that no one has ever bought it for in hopes they can make themselves rich. All my prices for musical instruments and scientific electronic test instruments are fair going rate prices. Please be aware that it takes quite a bit of time and effort to get a shipping quote so please be considerate of the seller if you are not ready to buy. Generally worldwide shipping is really cheap compared to other sellers because I have a 50% discount with fedex priority express thru my friend, I ship anywhere in the world !!!! Please email me your address for shipping quote if outside the USA .I fully insure all Items and pack everything extremely well! Also If you buy the item> please send your address in this format: Name: Street address: City: State/Province: Area code/zip Code: Country: Phone Number : Make sure you send your phone number! it is required for national and international shipping! : Pickup is completely fine as well> I am located 50 minutes from Los Angeles CA
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