Check Saw Out Signal Amplitude

6. Check Saw Out Signal Amplitude

DISPERSION RANGE

kHz/DIV

DISPERSION

100 kHz/div

a. Requirement--SAW OUT signal amplitude is 70 to

RESOLUTION

100 kHz (fully cw)

90 mV.

IF ATTENUATOR

OFF

b. Connect the test oscilloscope probe to the SAW OUT

VERTICAL DISPLAY

LIN

connector on the rear panel of the Type 491. Adjust the

test oscilloscope triggering controls for a triggered sweep

Band Selector

ramp display.

TIME/DIV

1 ms

c. Measure the amplitude of the sawtooth waveform.

VARIABLE

CAL

Must measure between 70 and 90 mV.

SOURCE

LINE

d. Disconnect the test oscilloscope from the SAW OUT

LEVEL

Triggered

sweep

connector.

c. Adjust the GAIN control far a signal amplitude of

approximately 6 divisions.

7. Check External Triggering

d. Decrease the DISPERSION to 0, keeping the signal

centered on screen with the IF CENTER FREQ controls.

a. Requirement--Sweep circuit must trigger on an exter-

nally applied signal of 0.2 V within the frequency range of

e. Switch the SOURCE switch to INT position and adjust

20 Hz to 100 kHz.

the LEVEL control for a triggered display.

b. Apply the output of the Audio Signal Generator

f. Adjust the position control to position the 1st marker to

through a coaxial cable and T connector to the rear panel

the 1st graticule line (see Fig. 5-1), then check the sweep

TRIG IN connector. Monitor the applied signal with the test

timing for each position of the TIME/DIV selector. Marker

oscilloscope by connecting a coaxial cable between the T

input, TIME/DIV selector and type of display is listed in Table

connector and the oscilloscope vertical Input connector.

5-1.

c. Set the Signal Generator frequency to 20 Hz and adjust

the output control for a signal amplitude of 0.2 V peak to

peak.

d. Change the Type 491 SOURCE switch to EXT position.

Adjust the LEVEL control and check for a triggered sweep

with the SLOPE switch in either the + or - positions. Must

trigger with a 20 Hz, 0.2 V externally applied signal.

e. Change the Signal Generator frequency to 100 kHz

and adjust the output control for a 0.2 volt peak to peak

signal.

f. Adjust the LEVEL control and check for a triggered

sweep with the SLOPE switch in either the + or - posi-

tions. Must trigger with a 100 kHz, 0.2 volt signal.

g. Remove the externally applied signal and T connector

from the Type 491 TRIG IN connector.

8. Check Line Triggering

a. Requirement-Sweep will trigger on LINE with the

LEVEL control centered and the SLOPE switch in either posi-

tion.

b. Set the SOURCE switch to LINE position.

c. Check for a triggered sweep with the LEVEL control

Fig. 5-1. Time markers aligned to check sweep timing.

centered and the SLOPE switch in either the + or - posi-

tions.

g. Return the TIME/DIV selector to 1 ms position, then

apply 10 ns and 5 ms markers to the Type 491.

9. Check Sweep Timing

h. Turn the VARIABLE control fully counterclockwise.

a. Requirement-Sweep timing accuracy must be within

±3% of indicated TIME/DIV selector Position.

i. Check-A minimum of five (5 ms) markers should be

displayed within the 10 division graticule width. Variable

b. Apply 10 ns and 1 ms time markers from the Time-Mark

control range 2.5:1.

Generator through 40 dB attenuator to band A, RF INPUT

j. Return the VARIABLE control to the CAL position.

connector. Set the front panel controls as follows:

5-3