Ch1/Ch2 Voltmeter Measurements; Dc Volts Accuracy; Dc Volts Normal Mode Rejection Ratio - Tektronix 2246 1Y Service Manual

CH1/CH2 VOLTMETER MEASUREMENTS

Equipment Required (See Table 4-1)
Calibration generator
Leveled sine-wave generator
Function generator

1. DC Volts Accuracy

a. Set:
READOUT (Intensity)
A INTEN
Vertical MODE
CH 1 VOLTS/DIV
CH 2 INVERT
SCOPE BW
CH 1 Input COUPLING
Horizontal MODE
A SEC/DIV
A/B SELECT
Trigger MODE
Trigger CPLG
Trigger SOURCE
Trigger SLOPE
Trigger HOLDOFF
CH1/CH2 VOLTMETER
FOCUS
Horizontal POSITION
b. CHECK—ground readout is 0.0 mV ±1.2 mV.
c. Set calibration generator
Square Wave/DC switch to DC.
NOTE
The PG 506 must be removed from the TM
power supply to make the change to dc output
from the generator. Turn the power off before
removing or inserting any plug-in from the TM
power supply
d. Connect the calibration generator Std Ampl out­
put to the CH 1 input via a 5 0 -0 precision BNC
coaxial cable.
REV OCT 1991
Performance Check Procedure—2246 1Y and 2246 Mod A Service
e.
f.
For a viewable
readout
For a viewable
trace
g-
CH 1
50 mV
h.
Off
Off
i.
GND
A
1 ms
j-
A Trigger
AUTO LEVEL
DC
k.
VERT
1 .
_r (positive)
Min
DC
m
For best
defined display
12 o 'clock
n.
2.
a.
(PG 506) internal
b.
c.
d.
e.
f.
50 O BNC coaxial cable
50 O BNC termination
Set calibration generator for Std Ampl output of
50 mV dc.
Set:
CH 1 VOLTS/DIV
CH 1 Input COUPLING
CHECK—the readout is between 49.0 mV and
51.0 mV.
Set CH 1 VOLTS/DIV to 0.1 V.
Set calibration generator for Std Ampl output
0.5 V.
CHECK—the readout is between 0.495 V and
0.505 V.
Set CH 1 VOLTS/DIV to 1 V.
Set calibration generator for Std Ampl output of 5
V.
CHECK—the readout is between 4.95 V and
5.05 V.
Disconnect Std Ampl signal from the CH 1 input.

DC Volts Normal Mode Rejection Ratio

Set SEC/DIV to 5 ms.
Connect function generator (FG 502) output to
the CH 1 input via a 5 0 -0 BNC coaxial cable and
BNC coupling capacitor.
Set function generator for a six-division sine-
wave display amplitude at 50 Hz (with CH 1
VOLTS/DIV at 1 V ).
Set CH 1 VOLTS/DIV to 0.2 V.
CHECK—that the readout is less than ±0.018 V.
Disconnect the function generator signal from the
2246 1Y or 2246 Mod A.
10 mV
DC
4-25