HP Car 3490A manual V e, T a Vc-vs, T s, 100, 179Using.theAcquire/HoldMode

SectionIII

v s - v e

Slope AB = -

T s - T a

Vc-vs

Slope BC = -

T c - T s

SlopeBC- SlopeAB

% Non-Linearity =	x 100
	SlopeAB

,"1

A ",1 DELAYEDSWEEP GATE OUTPUT

A

Figure3-13. UsingDelayed-SweepOscilloscopeinRamPLinearitYMeasurements.

&178. Filter ResponseMeasurementAided by an Oscil- loscope. Measurementof filter responsemay be accom- plished by the use of Sample/Hold, a delayed-sweep oscilloscope,a squarewavegenerator,and a time interv-al counter. The following proceduretests the responsetiniö ofa filter.

a.Choosean oscilloscopewith delayedsweep,such as the -hp-Model l80C with the 1821A Time Base/ Delay Generator plug-in unit. The vertical plug-in may be either single- or dual-channel. However, the dual- channel feature permits display of both the filter input and output at the sametime. Be sure the DelayedGate output from the oscilloscopemeets the Sample/Hold Trigger input signal requirements given in Paragraph 3-160.

5 o 6 m H5e6 mH

Model3490A

b. Connect the Delayed Gate output from the oscilloscopeto the S/H AC Trigger input. If the 3490A has Option 020 installed, connect the S/H Stretched Pulse Output to the Extemal Encode input (see Para- graph3-170).

c.Connect both the Main Gate and Delayed Gate

outputs from the oscilloscopeto an interval timer, such as the -hp-Model 5300A15302ACounter,to determine the time delay accurately.

d.Connect a squarewave generator,such asthe -hp-Model 33llA Function Generator, to both the filter input and the oscilloscopeinput. Set the square wave output to l0 V at a frequency such that the duration of one half of the squarewave is greaterthan the expected responsetime of the filter. For example,a frequencyof 300 Hz is satisfactory for the filter shown in Figure 3 - 14 .

e.Setthe 3490A to the l0 V range,DC function and Track/Hold operation. Connectthe output of the filter to the 3490A input terminals. If a dual-channeloscillo- scopeis used,also connectthe hlter output to the other oscilloscopeinput.

f.Position the delayed sweep intensified trace to- ward the right side of one half of the squarewave and determinethe final value of the filter output.

g.Shift the intensified trace toward the left until the 3490A readingis reducedto within XVo or X mV of the final value noted in step f. The time interval counter displays the time required to settle to this value. The intensified trace may be positionedat the other points to observeany overshootor ringingin the filter oütput.

3-179Using.theAcquire/HoldMode.

3-180. Measuringa Step Input Voltage. The Acquire/ Hold mode of operation is useful for measuringa step input voltage becausethe Sample/Hold Trigger com- mand may be applied simultaneouslywith the input voltage step. The aperture time, which is the delay between receipt of a Sample/Hold Trigger and the beginning of a Hold mode, is of sufficient length to include the acquisitiontime, as shown in Figure 3-l 5.

3490A WTH

SAMPLE/HOLD

Figure3-14. FilterOutput Measurement.

_1-10