Tektronix TDS 420A, Service Manual, Page: 90 / 288

Performance Tests
4- 22
TDS 420A, TDS 430A & TDS 460A Service Manual
Table 4- 2: DC Offset Accuracy
Vertical
Scale Setting Vertical
Position
Offset Setting
Generator
Setting Offset
Accuracy Limits
1 mV 0 +1 V +1 V
±
5 mV
100 mV 0 +10 V +10 V
±
65 mV
1 V 0 +99.9 V +99.9 V
±
649.5 mV
b. Set the vertical scale: Set the vertical SCALE to one of the settings
listed in Table 4--2 that is not yet checked. (Start with the first
setting listed.)
c.
Set the offset:
Press the VERTICAL MENU button and then the Offset
main-menu button. Using the General Purpose knob, set the offset as
dictated by Table 4--2. (Start with the first setting listed.)
d. Set the generator: Set the DC calibration generator to match the vertical
scale as dictated by Table 4--2. (Start with the first setting listed.)
e.
Check against limits: Do the following subparts in the order listed.
H
Subtract the measured mean from the generator setting. The result is
the offset accuracy
H
CHECK that the offset accuracy is within the limits listed for the
current vertical scale setting.
H
Repeat substeps b through e until all vertical scale settings listed in
Table 4--2 are checked for the channel under test.
f.
Test all channels: Repeat substeps a through e for all input channels.
3. Disconnect the hookup:
a. Set the generator output to 0 V .
b. Then disconnect the cable from the generator output at the input
connector of the channel last tested.
Equipment
Required Two dual-banana connectors (Item 7)
One BNC T connector (Item 8)
One DC calibration generator (Item 10)
Two precision coaxial cables (Item 5)
Prerequisites See page 4--15.
Check DC Voltage
Measurement Accuracy
(Averaged)