Vertical Deflection; Variable Gain Control Range (Continuation Of 6.3.6) - Fluke Autoranging CombiScope PM3370B Service Manual

6 - 8
table II.
Input voltage
(pp)
0.6V
6V
- Press the ANALOG key ('DIGITAL MODE' is displayed briefly), and repeat the tests in this
chapter for the digital mode.
- Press the ANALOG key ('ANALOG MODE' is displayed briefly) to return to analog mode.
6.3.7

Vertical deflection; variable gain control range (continuation of 6.3.6)

This test checks the vertical VARiable gain control.
Settings/procedure:
1 - Apply a square-wave signal of 0.2V to input CH1 and press AUTOSET.
2 - Set CH1 to 50 mV/div and input coupling to DC. Using the CH1 POS control, center the
waveform in the screen.
3 - Select the VARiable mode by simultaneously pressing both AMPL keys. The readout changes
into 50.0 mV/div.
4 - Press the mV key to adjust an input sensitivity of 40.0 mV/div.
Requirements:
1 - Verify that the displayed amplitude is between 4.86 and 5.14 divisions (+/- 2.8%).
2 - Repeat the settings and procedure for CH2. For the PM3394B and PM3384B repeat the same
steps for CH3 and CH4.
6.3.8 Vertical deflection; input coupling (continuation of 6.3.7)
This test verifies the operation of the AC input coupling. Also, the operation of the ground (GND)
function is checked.
Settings/procedure:
1 - Switch the CH1 VARiable mode off by simultaneously pressing both AMPL/VAR keys. The
readout changes to 50 mV.
2 - CH1 sensitivity is 50 mV/div; the vertical deflection is now 4 divisions.
Requirements:
1 - Activate the CH1 GND function and verify that a horizontal line is displayed.
2 - Select the AC input coupling and verify that a 4 divisions square-wave signal is displayed.
Center this signal in the middle of the screen.
3 - Select the DC input coupling and verify that the 4 divisions square-wave signal moves up. This
shift is caused by the signal's positive dc component: this component is not blocked in DC
coupled mode.
Repeat the settings and procedure for CH2, CH3, and CH4. PM3370B/80B/90B: check CH2 and
TRIG VIEW via EXT TRIG input for AC and DC coupling.
Setting Requirements
analog mode
0.1V 5.82...6.18 div (±3%)
1V 5.82...6.18 div (±3%)
PERFORMANCE TEST
Requirements
digital mode
5.82...6.18 (±3%)
5.82...6.18 (±3%)