Time Interval and Frequency Counter

6 Front Panel Operationresolution. The maximum period measurable inthis mode is 1 s.In both period and frequency modes the statisticaldata is displayed with the number of significantdigits allowed by the SR620's resolution. Usinglonger gate times increases the resolution.GRAPHICS OUTPUTSIn addition to the 16 digit LED display the SR620'sscope and chart outputs may be used to give theuser alternative methods of viewing the data.SCOPE OUTPUTSThe SR620 may be attached to an oscilloscopeoperating in x-y mode to provide a graphicalpresentation of the output data. The oscilloscopeshould be set in x-y mode with sensitivities set to1V/div and the SR620's x and y rear paneloutputs attached.GRAPH TYPESThe SR620 can then display either a histogram ofnumber of samples vs. measured parameter forthe samples within a measurement, a stripchart ofmean values for successive measurements, or astripchart of jitter values for successivemeasurements. In histogram mode a new graphwill be displayed after each measurement of Nsamples is complete, showing the distribution ofsamples in that measurement. In the stripchartmodes a new point will be added to the graph aftereach measurement indicating the mean and jittervalues for that measurement. The display desiredis chosen by pressing the select button below theindicator LEDs. The data for all three graphs aresaved so that all of the graphs may be viewed bycycling through the three choices. The data, thescale values, and the cursor position are alldisplayed on the scope screen. In the stripchartmodes up to 250 points will be displayed. Whenthe display fills up new data will start to overwritethe old starting from the left. The graph may becleared by pressing the CLR button below thePRINT button.SCALING GRAPHSIn histogram mode the vertical scale, horizontalscale, and number of bins may be adjusted. In thestripchart modes the vertical scales may beadjusted. The easiest way to scale the graphs isto press the "AUTO" button to autoscale the graph.Autoscale will automatically adjust the scales sothat the data fits on the screen. In histogrammode the actual scaling of the graph does notoccur until the next measurement is complete.The scale may also be adjusted manually.Pressing the up and down arrow keys with thenormal display on the 16 digit LEDs will adjust thevertical scale on the displayed graph. In thehistogram mode , incrementing the vertical scalepast the largest value (200,000 / div) will changethe vertical scale to a log scale. To view thescales on the LED display press the "DISP"button. First, the cursor position (discussedbelow) will be displayed. Pressing the buttonagain will display the vertical graph scales in theappropriate units. In the histogram mode pressingthe button again will display the horizontal scaleand then the number of bins. The scales may beadjusted using the up and down arrow keys.When the REL is set the graphs are centeredabout the REL and, thus, very fine detail may beobserved on a large number.GRAPHICS CURSORThe displayed graphs have a moveable cursor thatallows one to read the values of individual pointson the screen. The cursor is represented onscreen by a dotted line. The cursor is moved bypressing the "DISP" button to display the cursorposition and using the up and down arrow keys tomove it about. The cursor x position is displayedon the LED display ( in the correct units of s, Hz,etc.) for the histogram display and measurementnumber for the stripcharts. Both the x and ypositions are displayed on the scope screen.GRAPHICS ZOOMThe SR620 has a feature which allows one tozoom in on any feature in a displayed histogram,this feature also allows the REL to be set to anyvalue desired. First, press the DISP button todisplay the cursor position. Then, move the cursoruntil it is at the desired position ( or the cursorvalue is the desired REL value if setting the REL).Push the "SET" button. This will set the REL tothe cursor position. Now, adjust the graphhorizontal scale to get the magnification desired.If setting the REL value, note that the amount thatthe cursor value changes for each press of thearrow keys is determined by the horizontalhistogram scale and that the scale may have to beadjusted to get the REL value desired.SR620 Universal Time Interval Counter