Tektronix CFG253 Manual

CFG253 Performance Verification & Adjustment Procedures
Page 1of 19 Procedure #: CP1005 Revision: A
p Service Procedures
Product: CFG253 3 Mhz Function Generator
Title: Performance Verification & Adjustment
Procedure #: CP1005 Revision: A
Prepared By: Roy Lindley
Measurement Business Service Support
REVISION LEVEL SUMMARY:
Revision # Date Initiator Level Change
From: To:
Description
A5/16/97 Roy Lindley n/a Initial release

CFG253 Performance Verification & Adjustment Procedures
Page 2of 19 Procedure #: CP1005 Revision: A
CFG253 PERFORMANCE VERIFICATION PROCEDURE
CONTENTS:
Preparation 3
Check DC Offset 3
Check Main Output Amplitudes 4
Square Wave Overshoot, Rise/Fall Time 6
Check Square Wave Duty Cycle 7
Sync (TTL) Output 8
Sine Wave Distortion 9
Frequency Dial Accuracy 9
INTRODUCTION
To ensure instrument accuracy, check its performance after every 2000 hours of operation or
once each year if used infrequently.
The instrument case does not have to be removed for the Performance Check procedure. All
necessary controls and connectors are accessible from the outside.
Test Equipment: Requirement: Example:
Test Oscilloscope 5mV-5V/Div, 50nS/Div Tek TDS210
Frequency Counter > 3MHz, < 1 % Tek CMC251
Distortion Analyzer 100KHz AA501A
Coax Cable 50 ohm P/N 012-0057-01
50 Ohm Terminator P/N 011-0049-01

CFG253 Performance Verification & Adjustment Procedures
Page 3of 19 Procedure #: CP1005 Revision: A
PREPARATION
Connect the instrument and test equipment to an appropriate power source and allow 20
minutes for warm up and stabilization. Set the controls as listed below during warm up.
Initial CFG253 Set-Up:
AMPLITUDE Mid Range
DC OFFSET Pushed In
SYMMETRY Midrange Detent
RANGE 1K
FUNCTION All Buttons Out
VOLTS OUT Button Out
FREQ/10 Button Out
SWEEP Button Out
SWEEP RATE Midrange
SWEEP WIDTH Midrange
FREQ DIAL 0.3
1. CHECK DC Offset
a. Pull out the DC OFFSET knob.
b. Test Scope Set-Up:
Volts/Div 2V
Time/Div 0.2 mSec
c. Connect MAIN OUTPUT to test scope vertical input via coax cable and 50 ohm
terminator.
d. Set test scope Vert Coupling to GROUND, center the trace, then set Coupling
back to DC.
e. While turning the DC OFFSET knob from CCW to CW and back, check for for >
+5 V with DC OFFSET knob CW and > -5 V with the knob CCW (+/- 2.5 Div on
test scope).
f. Push the DC OFFSET knob in (off).

CFG253 Performance Verification & Adjustment Procedures
Page 4of 19 Procedure #: CP1005 Revision: A
2. CHECK MAIN OUTPUT AMPLITUDES
a. Set-Up:
AMPLITUDE CW
DC OFFSET Pushed In
RANGE 1K
FUNCTION Triangle
VOLTS OUT Button Out
FREQ/10 Button Out
FREQ DIAL 3.0
b. Test Scope Set-Up:
Volts/Div 2V
Time/Div 0.2 mSec
c. Connect MAIN OUTPUT to test scope vertical input via coax cable and 50 ohm
terminator.
d. Check the test scope display for > 5 divisions (10V).
e. Rotate the AMPLITUDE knob to nearly CCW.
f. Set test scope to 10 mV/Div. Check that the display reduces to less than 5
divisions (50mV) as the AMPLITUDE knob approaches the CCW stop.
g. Set the VOLTS OUT button in and change the test scope Volts/Div to 5mV.
h. Check for a display of < 1 division (5mV) as the knob approaches the CCW stop.
i. Set the test scope Volts/Div to 0.2 V. Rotate the AMPLITUDE knob fully CW.
j. Check the display for > 5 divisions (1V).
k. Return the VOLTS OUT button to the out position and ensure that the
AMPLITUDE is CW.

CFG253 Performance Verification & Adjustment Procedures
Page 5of 19 Procedure #: CP1005 Revision: A
l. Set the FUNCTION to Square Wave. Use the CFG253 and test scope settings in
Table 1 to check the MAIN OUTPUT AMPLITUDE for the indicated settings :
TABLE 1
Function Range Volts Out
button
Freq.
Dial
Test Scope
Volts/Div
Test Scope
Display
Square Wave 1K Out 3.0 2V/Div > 5 Div
Sine Wave 1K Out 3.0 2V/Div > 5 Div
Sine Wave 1K Out 0.3 2V/Div > 5 Div
Square Wave 1K Out 0.3 2V/Div > 5 Div
Triangle 1K Out 0.3 2V/Div > 5 Div
m. Remove the 50 ohm terminator and connect the coax cable directly to the test
scope input.
n. Set the test scope Time/Div to 1uSec.
o. Check the test scope display for each setting in Table 2:
TABLE 2
Function Range Volts
Out
Freq.
Dial
Volts/D
iv
Display
Triangle 1M Out 3.0 5V/Div > 4 Div
SquareWave 1M Out 3.0 5V/Div > 4 Div
Sine Wave 1M Out 3.0 5V/Div > 4 Div
p. Press the VOLTS OUT button in. Check the test scope display for the settings in
Table 3:
TABLE 3
Function Range Volts
Out
Freq.
Dial
Volts/Div Display
Sine Wave 1M In 3.0 0.5V/Div > 4 Div
Square Wave 1M In 3.0 0.5V/Div > 4 Div
Triangle 1M In 3.0 0.5V/Div > 4 Div

CFG253 Performance Verification & Adjustment Procedures
Page 6of 19 Procedure #: CP1005 Revision: A
q. Rotate the AMPLITUDE knob nearly CCW.
r. Set the test scope Volts/Div to 5mV.
s. Check the display for < 2 divisions (10mV) as the knob nears the CCW stop.
3. Square Wave Rise Time and Fall Time
a. Test Scope Set-Up:
Volts/Div 5V
Time/Div 0.5 uSec
Trig Slope +
b. Set-Up:
AMPLITUDE CW
DC OFFSET Pushed In
RANGE 100K
FUNCTION Square Wave
VOLTS OUT Button Out
FREQ/10 Button Out
FREQ DIAL 3.0
c. Connect MAIN OUTPUT to test scope vertical input via coax cable WITHOUT
the 50 ohm terminator.
d. Adjust AMPLITUDE knob for a 4 division display on the test scope.
e. Set Time/Div to 50 nSec/Div. Adjust Trig Level control as necessary to display
the rising edge of the Square Wave.
f. Check risetime between the 10% and 90% points for < 100 nSec (2 Div).
g. Set test scope Trig Slope to - (negative). Adjust Trig Level to view the Falling
edge of Square Wave.
h. Check the Fall Time between the 10% and 90% points for < 100 nSec (2 Div).

CFG253 Performance Verification & Adjustment Procedures
Page 7of 19 Procedure #: CP1005 Revision: A
4. Check Square Wave Duty Cycles
a. Set-Up:
AMPLITUDE Midrange
RANGE 1K
FUNCTION Square Wave
FREQ/10 Button In
FREQ DIAL 3.0
b. Test Scope Set-Up:
Volts/Div 1V
AC/GND/DC DC
Time/Div 0.2 mSec
Trig Slope +
c. Connect MAIN OUTPUT to test scope vertical input via coax cable and 50 ohm
terminator. Adjust Trig Level as necessary for a stable display.
d. Use test scope variable Time/Div control to set the display for 1 complete cycle
over 10 divisions.
e. Check for nearly equal positive and negative half cycles (50 % duty cycle).
Readjust the variable Time/Div as necessary to maintain 1 complete cycle over
10 divisions.
f. Set FREQ/10 button out.
g. Check that the frequency increases by a factor of 10 as shown by a display of
approximately 1 cycle per division on the test scope.
h. Set the FREQ/10 button in. Rotate the SYMMETRY knob CCW and use the
Time/Div variable to set the first half cycle to 1 division. Rotate the SYMMETRY
knob CW and check for the same half cycle to increase to 5 divisions or greater (a
duty cycle change of 5:1).
i. Return the SYMMETRY knob to the center detent position and the test scope
Time/Div variable to the detent position.

CFG253 Performance Verification & Adjustment Procedures
Page 8of 19 Procedure #: CP1005 Revision: A
j. Repeat steps d and e to verify the 50 % duty cycles for the settings in Table 4.
Table 4
RANGE FREQ. DIAL FREQ/10 TIME/DIV RESULT
1K 3.0 OUT 20uSec 50 % Duty Cycle
1K 0.3 OUT 0.2mSec 50 % Duty Cycle
1K 0.3 IN 2 MSec 50 % Duty Cycle
100K 0.3 OUT 2 uSec 50 % Duty Cycle
1M 0.3 IN 2 uSec 50 % Duty Cycle
5. SYNC (TTL) OUTPUT
a. Set-Up:
AMPLITUDE CW
RANGE 1K
FUNCTION Triangle
VOLTS OUT Button Out
FREQ/10 Button Out
FREQ DIAL 3.0
b. Test Scope Set-Up:
Volts/Div 1 V
Time/Div 0.2 mSec
c. Connect SYNC/TTL OUTPUT directly to the test scope vertical input via a coax
cable (without the 50 ohm terminator).
d. Check the test scope for a display of approximately 4 volts (4 divisions).
e. Repeat step d with the FUNCTION set to Square Wave and Sine Wave.

CFG253 Performance Verification & Adjustment Procedures
Page 9of 19 Procedure #: CP1005 Revision: A
6. SINE WAVE DISTORTION
a. Set-Up:
RANGE 100K
FUNCTION Sine Wave
VOLTS OUT Button Out
FREQ/10 Button Out
FREQ DIAL 1.0
b. Connect MAIN OUTPUT to Distortion Analyzer via coax cable and 50 ohm
terminator.
c. Set the Distortion Analyzer INPUT RANGE to Auto Range, and the FUNCTION
settings to Volts, Auto Range and THD+N.
d. CHECK- For less than 1% distortion for the frequencies listed in Table 5:
Table 5
RANGE FREQ DIAL PER CENT
DISTORTION
100K 1.0 < 1 %
10K 1.8 < 1 %
1K 1.8 < 1 %
100 1.8 < 1 %
10 1.0 < 1 %
7. FREQUENCY DIAL ACCURACY
a. Set-Up:
AMPLITUDE CW
RANGE 1K
FUNCTION Triangle
VOLTS OUT Button In
FREQ/10 Button Out
FREQ DIAL 3.0

CFG253 Performance Verification & Adjustment Procedures
Page 10 of 19 Procedure #: CP1005 Revision: A
b. Connect the CFG253 MAIN OUTPUT to the input of a Frequency Counter.
Check the frequency reading for each set-up listed in Table 6:
Table 6
RANGE FREQ DIAL COUNTER READING
1 M 3.0 2.85 MHz - 3.15 MHz
1 M 0.3 150 KHz - 450 KHz *
100 K 3.0 285 KHz - 315 KHz
10 K 3.0 28.5KHz - 31.5KHz
1 K 3.0 2.85KHz - 3.15KHz
100 3.0 285 Hz - 315 Hz
10 3.0 28.5 Hz - 31.5 Hz
13.0 2.85 Hz - 3.15 Hz
*The Frequency reading accuracy is 5% of full scale. 5% of 3 MHz is 150
KHz
c. Disconnect cable from the Counter and CFG253.