Tektronix DC 503A Technical Manual
TM 9-6625-474-14&P-3
TECHNICAL MANUAL
OPERATOR, ORGANIZATIONAL,
DIRECT SUPPORT, AND GENERAL SUPPORT
MAINTENANCE MANUAL
(INCLUDING REPAIR PARTS)
FOR
UNIVERSAL
TEKTRONIX,
COUNTER/TIMER,
MODEL DC 503A
(NSN 6625-01-114-4890)
DEPARTMENT OF THE ARMY
26 DECEMBER 1984
WARNING
DANGEROUS VOLTAGE
is used in the operation of this equipment
DEATH ON CONTACT
TM 9-6625-474-14&P-3
personnel fail to observe safety precautions
t if
. .
Never work
may resul
on
electronic equipment unless there is another person nearby who is familiar with the
operation and hazards of the equipment and who is competent in administering first aid. When the
technician is aided by operators, he must warn them about dangerous areas.
Whenever possible, the power supply to the equipment must be shut off before beginning work on the
equipment. Take particular care to ground every capacitor likely to hold a dangerous potential. When
working inside the equipment, after the power has been turned off, always ground every part before
touching it.
Be careful not to contact high-voltage connections when installing or operating this equipment.
Whenever the nature of the operation permits, keep one hand away from the equipment to reduce the
hazard of current flowing through vital organs of the body.
WARNING
Do not be misled by the term “low voltage.”
Potentials as low as 50 volts may cause death under adverse
conditions.
COMMON
any is present on each -
and probe ground straps are electrically connected. Herefore, an elevated reference applied to
as indicated by the yellow warning bands under the probe retractable hook tips.
For Artificial Respiration, refer to FM 21-11,
Power Source
This product is intended to operate in a power module connected to a power source that will not apply more
than 250 volts rms between the supply conductors or between either supply conductor and ground. A
protective ground connection by way of the grounding conductor in the power cord is essential for safe
operation.
a/(b blank)
Copyright 1980 Tektronix, Inc. All rights reserved.
Reproduced by permission of copyright owner.
TM 9-6625-474-14&P-3
TECHNICAL MANUAL
DEPARTMENT OF THE ARMY
No. 9-6625-474-14&P-3
Washington, D. C.,
OPERATOR, ORGANIZATIONAL, DIRECT SUPPORT,
AND GENERAL SUPPORT MAINTENANCE MANUAL
(INCLUDING REPAIR PARTS)
FOR
UNIVERSAL COUNTER/TIMER,
TEKTRONIX, MODEL DC 503A
(NSN 6625-01-114-4890)
REPORTING OF ERRORS
You can help improve this manual. If you find any mistakes or if you know of a way
to improve the procedures, please let us know. Mail your Ietter or DA Form 2028
(Recommended Changes to Publications and Blank Forms), direct to: Commander, US Army Missile Command, ATTN: DRSMI-SNPM, Redstone Arsenal, AL
35898-5238. A reply will be furnished to you.
TABLE OF CONTENTS
LIST OF ILLUSTRATIONS
LIST OF TABLES . . . . . . . . . . . . . . . . . . .
SECTION 0
SECTION 1.
SECTION 2.
SECTION 3.
SECTION 4.
SECTION 5.
GENERAL NFORMATION
Scope
indexes of Publications
Forms, Records, and Reports
Reporting Equipment Improvement Recommendations (EIRs)
Administrative Storage
Destruction of Army Electronics Materiel.
SPECIFICATION . . . . . . . . . . . . . . . . . . .
THEORY OF OPERATION.
MAINTENANCE
HEADQUARTERS
26 December 1984
Page
iii
IV
0-1
0-1
0-1
0-1
0-1
0-1
0-1
1-1
2-1
2-1
2-2
2-4
2-4
2-5
2-7
3-1
4-1
4-1
4-8
5-1
This manual is, in part, authenticated manufacturer’s commercial literature. Recommended Spare Parts List has been added to supplement the commercial
literature. The format of this manual has not been structured to consider levels of maintenance.
TM 9-6625-474-14&P-3
SECTION 6.
SECTION 7.
SECTION 8.
SECTION 9.
APPENDIX A.
APPENDIX B.
APPENDIX C.
APPENDIX D.
OPTIONS
REPLACEABLE ELECTRICAL PARTS
DIAGRAMS AND CIRCUIT BOARD ILLUSTRATIONS
REPLACEABLE MECHANICAL PARTS
REFERENCES
MAINTENANCE ALLOCATION CHART (MAC)
RECOMMENDED SPARE PARTS LIST
MANUAL CHANGE INFORMATION
TABLE OF CONTENTS (CONT)
Page
6-1
7-1
8-1
9-1
A-1
B-1
C-1
D-1
ii
LIST OF ILLUSTRATIONS
TM 9-6625-474-14&P-3
Fig. No.
0-1
2-1
2-2
2-3
2-4
2-5
2-6
3-1
4-1
4-2
4-3
4-4
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
Title
DC 503A Universal Counter/Timer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Plug-ln lnstallation/Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Controls and Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Triggering Circuit Response to Improper (A) and
Proper (B) Level Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Representation of lnterval Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical CHAand CH B Level out Voltage Settings for
Various Time interval Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Illustration ofCH A Events Counted from Portion of
CH A Signal Pulses during the Counter Gate Open
Time (Controlled by the CH B Signal) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical DC 503A Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Check Set-Up for the High Frequency Sensitivity
Using X1 and X5 Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Check Set-Up for Low Frequency ac and dc Sensitivity . . . . . . . . . . . . . . .
Check Set-Up for Minimum Pulse Width Signals . . . . . . . . . . . . . . . . . . . . .
Check Set-Up for Trigger Level Range (3.5V) and
Accuracy
(Y20mVf0.59’0
of Reading) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical Square Pin Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exploded View of Circuit Board Pin and Ferrule . . . . . . . . . . . . . . . . . . . . . .
Dual Entry Circuit Board Pin Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bottom Entry Circuit Board Pin Socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Orientation and Disassembly of Multipin Connectors . . . . . . . . . . . . . . . . .
Rear Frame Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Board Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pushbutton Switch Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear Interface Connector Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear Interface Timing for a Display of 1079.0674 . . . . . . . . . . . . . . . . . . .
Page
0-2
2-1
2-3
2-5
2-9
2-10
2-11
3-5
4-4
4-6
4-8
4-12
5-3
5-3
5-4
5-4
5-4
5-5
5-5
5-5
5-7
5-8
iii
TM 9-6625-474-14&P-3
LIST OF TABLES
Table No.
1-1
1-2
1-3
1-4
2-1
2-2
2-3
2-4
2-5
3-1
4-1
5-1
Title
Electrical Characteristics . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Environmental . . . ....... . . . . . . . . . . . . . . . . . . . . . . . . . . .
Physical Characteristics ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Frequency A Display Check. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Page
1-2
1-7
1-7
1-8
2-5
Period B, Time A-B, Width B (Timing Mode)
Display Check
2-6
Period B, Time A- B, Width B (Averaging Mode)
Display Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ratio A/B and Events A During B Display Check . . . . . . . . . . . . . . . . . . . . .
Gate Time vs Measurement Resolution . . . . . . . . . . . . . . . . . . . . . .
PROM Selection Code . . . . . . . . . . . . . . . . . . . . . . . . . . . .
List of Test Equipment Requirements . . . . . . . . . . . . . . . . . . . .
Relative Susceptibility to Static Discharge Damage
2-6
2-6
2-8
3-10
4-2
5-1
iv
SECTION 0
GENERAL INFORMATION
TM 9-6625-474-14&P-3
0-1. Scope. This manual contains instructions for
the operator, organizational, direct support, and general support maintenance of and calibration procedures for Tektronix Universal Counter/Timer, Model DC
503A. Throughout this manual, Tektronix Universal
Counter/Timer, Model DC 503A is referred to as the
DC 503A.
0-2. Indexes of publications. a. DA Pam 310-4.
Refer to the latest issue of DA Pam 310-4 to determine whether there are new editions, changes, or
additional publications pertaining to Tektronix Universal Counter/Timer, Model DC 503A.
b. DA Pam 310-7. Refer to the latest issue of DA
Pam 310-7 to determine whether there are modification work orders (MWO’S) pertaining to Tektronix
Universal Counter/Timer, Model DC 503A.
0-3. Forms, Records, and Reports. Department of
Army forms and procedures used for equipment maintenance and calibration are those prescribed by TM
38-750, The Army Maintenance Management System.
Accidents involving injury to personnel or damage to
materiel will be reported on DA Form 285, Accident
Report, in accordance with AR 385-40.
0-4. Reporting Equipment Improvement Recommendations (EIR). If your DC 503A needs im-
provement, let us know. Send us an EIR. You, the
user, are the only one who can tell us what you don’t
like about your equipment. Let us know why you don’t
like the design. Tell us why a procedure is hard to
perform. Put it on an SF 368 (Quality Deficiency
Report). Mail it to Commander, U.S. Army Missile
Command, ATTN: DRSMI-QMD, Redstone Arsenal,
AL 35898-5290. We’ll send you a reply.
0-5. Administrative Storage. To prepare the Tektronix Universal Counter/Timer, Model DC 503A for
placement into and removal from administrative storage, refer to Section 3, Chapter 4, AR 750-25-1,
Maintenance of Equipment and Supplies. Temporary
storage should be accomplished in accordance with
TB 750-25-1, Section 2, Maintenance of Supplies and
Equipment.
0-6. Destruction of Army Electronics
Materiel. Destruction of Tektronix Universal Counter/
Timer, Model DC 503A to prevent enemy use shall be
in accordance with TM 750-244-2.
0-1
TM 9-6625-474-14&P-3
0-2
Fig. 0-1. DC 503A Universal Counter/Timer
SECTION 1
SPECIFICATION
TM 9-6625-474-14&P-3
Instrument Description
The DC 503A Universal Counter/Timer is designed to
operate in a TM 500-series power module.
The instrument has two input channels, CH A and CH
B, each with 125 MHz capability. Each channel has
separate triggering level, triggering slope, attenuator, and
coupling mode controls.
The DC 503A has eight measurement functions: FREQUENCY A, PERIOD B, WIDTH B, TIME A - B,
RATlO A/B, EVENTS A DURING B, TOTALIZE A, and
TIME MANUAL. All of the modes except FREQUENCY A,
TOTALIZE A, and TIME MANUAL have the capability of
averaging the selected measurement over a range of 1 to
10*
times the input signal. The signals to be counted or
measured can be applied via front panel bnc connectors or
through the rear Interface.
The triggering level for each channel can be monitored
via the front panel or the rear i nterface connections. The
buffered voltage available at these connectors corresponds to the trigger levels set by the front panel
controls.
The output of the internal signal shaping circuits can
also be monitored via front panel connectors. These
shaped signal outputs are useful in setting the triggering
points on complex waveforms.
Instrument Options
Option 01 replaces
(clock) circuit with
temperature controlled oven oscillator for increased accuracy and stability.
Standard Accessories
1 Instruction Manual
1 Cable assembly, bnc-to-tip jack.
Refer to the tabbed Accessories page at the rear of
this manual for more information.
Performance Conditions
The limits stated in the Performance Requirements
columns of the following tables are valid only if the
DC 503A has been calibrated at an ambient temperature
between +20°C and +30°C and is operating at an ambient
temperature between
stated.
the internal 10 MHz time base
a self-contained proportional
NOTE
O“C
and
+50”C,
unless otherwise
Measurement results are displayed in an eight digit
LED readout. The decimal point is automatically positioned and leading zeros are blanked. Single annunciators
(LEDs) are used to indicate register overflow, active gating
interval, and the frequency or time units associated with
the measurement being made.
The DC 503A can be equipped with an optional, oven
controlled, 10 MHz crystal oscillator to obtain a highly
stable and precise internal time base. Both the optional
oscillator and the standard 10 MHz time bases provide
100 ns single shot resolution.
Information given in the Supplemental Information and
Description columns of the following tables is provided for
user information only and should not be interperted as
Performance Check requirements.
The DC 503A must be operated or stored in an
environment whose limits are described under Environmental Characteristics.
Allow at least 20 minutes warm-up time for operation to
specified accuracy, 60 minutes after storage in a high
humidity environment.
1-1
TM 9-6625-474-14&P-3
Table 1-1
1-2
Table 1-1
TM 9-6625-474-14&P-3
1-3
TM 9-6625-474-14&P-3
Table 1-1
1-4
Table 1-1
TM 9-6625-474-14&P-3
1-5
TM 9-6625-474-14&P-3
Table 1-1
1-6
Table 1-1
Table 1-2
TM 9-6625-474-14&P-3
Table 1-3
1-7
TM 9-6625-474-14&P-3
Table 1-3
Table 1-4
1-8
TM 9-6625-474-14&P-3
SECTION 2
OPERATING INSTRUCTIONS
INTRODUCTION
This section of the manual provides installation and
removal instructions and the operating information re-
quired to obtain the most effective performance from the
instrument. Also included is the function of all front panel
controls and a general description of the operating modes,
which also describes procedures for making basic
measurements.
INSTALLATION AND REMOVAL
The DC 503A is calibrated and ready to use when
received. It operates in one compartment of a TM 500-
Series power module. Refer to the power module instruc-
tion manual for line voltage requirements and power
module operation.
To prevent damage to the DC 503A, turn the power
module off before installation or removal of the
instrument from the mainframe. Do not use excessive force to install or remove.
press firmly to seat the circuit board edge connector in the
power module interconnecting jack. Apply power to the
DC 503A by operating the power switch on the power
module.
To remove the DC 503A from the power module, pull
the release latch (located in the lower left corner) until the
interconnecting jack disengages. The DC 503A will now
slide straight out.
Check to see that the plastic barriers on the inter-
connecting jack of the selected power module compart-
ment match the cutouts in the DC 503A circuit board edge
connector. If they do not match, do not insert the
instrument until the reason is investigated. When the units
are properly matched, align the DC 503A chassis with the
upper and lower guides of the selected compartment (see
Fig. 2-1). Insert the DC 503A into the compartment and
Fig. 2-1. Plug-in installation/removal.
2-1
TM 9-6625-474-14&P-3
CONTROLS AND CONNECTORS
Even though the DC 503A is fully calibrated and ready
to use, the functions and actions of the controls and
connectors should be reviewed before attempting to use
it.
With the exception of the TOTALIZEA/TIME MANUAL
jumper, which is described in the maintenance section, all
controls for operation of the DC 503A are located on the
front panel. A brief functional description of these controls
follows (refer to Fig. 2-2).
NOTE
Because the Channel A and Channel B controls are
identical, only Channel A will be described.
DISPLAY AND UNIT INDICATORS
DISPLAY READOUT: eight-digit, seven segment
LED readout with automatically positioned decimal
point.
OVERFLOW: when illuminated indicates register
overflow.
MODE SELECTION AND
CONTROL FUNCTIONS
FUNCTION: selects the measurement, events, or
time counting modes for the counter.
NOTE
The TOTALIZE A/TIME MANUAL position is an
"either/or"
MANUAL is selected and set by positioning an
Internal jumper. Placement of this jumper is discussed in the maintenance section.
Unless you are qualified to do so, refer positioning of
this jumper to qualified personnel.
AVGS/TIMING: depending on the position of the
FUNCTION switch, this switch selects the clock rate
which will be counted or the number of
measurements to be averaged.
function.
TOTALIZE A or TIME
GATE: indicates the state of the main gate. When lit,
the main gate is open (the DC 503A is in the process
of making a measurement). When the light is off, the
gate is closed.
GHz/nSEC: when illuminated, indicates the displayed number is gigahertz (GHz) in FREQ A mode
or nanoseconds (nSEC) in a time mode.
MHz/uSEC:
played number is Megahertz (MHz) in FREQ A mode
or microseconds
kHz/mSEC: when illuminated, indicates the displayed number is kilohertz (kHz) in FREQ A mode or
milliseconds (m SEC) in a time mode.
Hz/SEC: when illuminated, indicates the displayed
number is Hertz (Hz) in FREQ A mode or seconds
(SEC) in a time mode.
when illuminated, indicates the dis-
(HSEC)
in a time mode.
2-2
DISPLAY TIME: sets the length of time the reading
will be displayed after the count is made and before
the next measurement is taken, Display time can be
varied from about 0.1 second, fully counterclockwise (ccw), to about 10 seconds fully clockwise
(cw). The HOLD position provides continuous display until reset by pushing the RESET button,
RESET: momentary switch resets the count to zero
when operating in the TOTALIZE A mode. Also acts
as a master reset, ensuring that the readout has been
cleared before the next measurement. Provides a
check of all display LED’s; when pressed, a row of 8’s
will be displayed in the readout window.
START/STOP: push-push switch acts as a manual
gate when the FUNCTION switch is in the
TOTALIZE A/TIME MANUAL position. Button in
Starts the measurement interval gate; button out
terminates the gate.
TM 9-6625-474-14&P-3
Fig. 2-2. Controls and connectors.
2-3
TM 9-6625-474-14&P-3
CHANNEL A INPUT AND LEVEL
FUNCTIONS
CH A INPUT: bnc connector for Channel A signal
input. Input impedance is 1 shunted by approximately 20 pF.
LEVEL: selects the amplitude point on the positive or
negative slope of the input signal at which the
triggering window is placed.
SLOPE: push-push switch selects the slope of the
input signal on which triggering will occur, Button
out selects plus (+) slope; button in minus (–) slope.
ATTEN: push-push switch selects X1 (button out) or
X5 (button in) attenuation of the input signal.
COUPL: push-push switch selects DC (button out)
or AC (button in) coupling of the input signal to the
attenuator circuit.
SOURCE: push-push switch selects the source of
the input signal. Button out, EXT, selects the front
panel connector as a signal source. Button in, INT,
routes the input signal to the counter via the rear
interface connections.
SHAPED OUT A: provides a shaped output signal
derived from the output of the Channel A signal
shaper circuitry.
SHAPED OUT GND: common connector for
Channel A shaped output signals.
TRIG LEVEL A: pin jack permits monitoring of the
Channel A triggering voltage level.
RELEASE LATCH: pull to disengage and remove
DC 503A from the power module.
INPUT CONSIDERATIONS
Input Sources
NOTE
Maximum input voltage limited to 200 V peak.
The SOURCE switch for each channel selects either the
front panel bnc connector (external), or the rear interface
connector (internal) pins. The external inputs present
impedances of approximately 1 paralleled by about 27
pF. The internal input circuits present nominal 50
impedances to match typical coaxial cable signal connections.
Input Coupling
Front panel pushbuttons select ac (capacitive) or dc
(direct) coupling for the input signal of each channel. This
coupling takes place before the signals are passed into the
attenuator circuits.
Attenuators and Maximum Input Volts
For either attenuation factor, X1 or X5, the maximum
safe input voltatage that can be applied to the front panel
bnc connectors is 200 V (peak) from dc to 50 kHz. At
frequencies above 50 kHz, the maximum safe peak-to-
peak input voltage tothe front panel bnc connectors must
be calculated (see Specification section). The maximum
safe input voltage to the rear interface input connectors is
equal to or less than 4 V (dc plus peak ac) from dc to
50 MHz.
Sensitivity and Frequency Range
CH A and CH B will respond to a signal amplitude of
20 mV rms sinewave, times attenuation, to lOO MHzandto
a sinewave of 35 mV rms, times attenuation, to 125 MHz.
[)
Depending on the coupling mode selected, the low
frequency limit for each channel is either zero (dc
coupled) or 10 Hz (ac coupled).
Slope and Level
The SLOPE pushbuttons for each channel determine
whether the trigger circuits will respond to the negative or
positive transition of the input signal.
Refer to Fig. 2-3. The LEVEL control for each channel
allows the operator to move the hysteresis window of the
trigger circuit to an optimum level on the input signal to
ensure stable triggering The LEVEL control adjusts over
+3.5 V, times attenuation, of the input signal. This level
can bemoniiored atthefront panel TRIG LEVEL pin jacks.
2-4
TM 9-6625-474-14&P-3
Fig. 2-3. Triggering circuit response to improper (A) and proper (B) level settings.
OPERATORS FAMILIARIZATION
PREPARATION
Turn on the power module to apply power to the
DC 503A. One or more characters in the display should be
visible. Allow twenty minutes warm-up time for operation
to specified accuracy.
DISPLAY TESTS
With no signal applied, test the DC 503A readout
displays and switching logic. The following checks will
test most of the major circuits of the counter and ensure its
readiness to make measurements. If any malfunctions are
encountered, refer
personnel.
Readout Segment
Press the RESET
segments of each digit. A row of 8's should be displayed.
This check of the display devices can be done at anytime.
the condition to qualified service
Test
button to check the seven character
Table 2-1
FREQUENCY A DISPLAY CHECK
With the DISPLAY TIME control in the fully
counterclockwise position, observe that the GATE indicator flashes rapidly for short gate times and more
slowly for longer gate times. Using a short gate time
(100 ms), rotate the DISPLAY TIME control slowly
clockwise. Observe that the GATE indicator stays off for a
longer and longer time, until the control clicks into the
HOLD (detent) position, holding off the gate indefinitely.
Return
counterclockwise position.
the DISPLAY TIME control to the
Frequency A Displays
Set the FUNCTION switch to FREQUENCY A. With the
AVGS/TIMING switch, select a gate time of 100 ns. Check
the decimal point location, leading zero suppression, and
units indicators according to Table 2-1.
Period B, Width B, and Time A - B Displays
Timing Mode. Set the FUNCTION switch to PERIOD B
in the blue area of the front panel and the AVG/TIMING
switch to 100 ns. Observe the correct readout displays as
shown in Table 2-2.
2-5
TM 9-6625-474-14&P-3
Table 2-2
PERIOD B, TIME A - B, WIDTH B
(TIMING MODE) DISPLAY CHECK
Set the FUNCTION switch to WIDTH B in the blue area
of the front panel while retaining the setting of the
AVG/TIMING switch; observe the correct readout display.
Set the FUNCTION switch to TIME A - B in the blue
area of the front panel while retaining the setting of the
AVG/TIMING switch; observe the correct readout display.
Table 2-4
RATIO A/B AND EVENTS A
DURING B DISPLAY CHECK
Time Manual Displays
Verify that the jumper located on the Auxiliary Circuit
Board is in the TIME MANUAL position. Set the FUNCTION switch to the TIME MANUAL Position and the
AVGS/TIMING switch to 1 sec.
Averaging Mode. Repeat the preceding checks for
these functions in the dark grey area of the front panel.
Observe the correct readout display for each switch
setting as shown in Table 2-3.
Table 2-3
PERIOD B, TIME A - B, WIDTH B
(AVERAGING MODE) DISPLAY CHECK
Events A During B and Ratio A/B Displays
Set the FUNCTION switch to EVENTS A DURING B
and the AVGS/TIMING switch to 1. Check the readout
displays according to Table 2-4.
Set the FUNCTION switch to RATlO A/B and the
AVGS/TIMING switch to 1. Again check the readout
displays using Table 2-4.
The GATE indicator should light and an advancing
count should be displayed when the START/STOP button
is pushed in. The GATE indicator should go out when the
count is stopped by releasing the START/STOP button.
Check the overflow display by setting the AVGS/TIMING
switch to 100 ns pressing the START/STOP button in, and
letting the count advance, When the last decade (eighth
digit) goes from nine to zero the OVERFLOW indicator will
light. Release the START/STOP button and observe that
the OVERFLOW indicator remains on, but the count does
not change. Pressing the RESET button clears the
overflow condition, sets the count to zero, and extinguishes the OVERFLOW indicator.
Totalize A Display
For this check, the jumper located on the Auxiliary
Circuit Board must be in the Totalize position.
Unless you are qualified to do so, refer placement of
this jumper to qualified personnel.
Set the FUNCTION switch to the TOTALIZE A/TIME
MANUAL position. Observe a zero at the right of the
readout display. The GATE indicator should light when
the START/STOP button is pushed in, and go out when
the button is released. The units indicators and decimal
points should remain off.
2-6
TM 9-6625-474-14&P-3
Channel A Slope
Verify that the TOTALIZE/TIME MANUAL jumper is in
the TOTALIZE position. With the FUNCTION switch set to
TOTALIZE A/TIME MANUAL and CH A to + SLOPE
(button out), press the START/STOP button. Turn the CH
A LEVEL control fully clockwise. The readout display
should increase one count each time the control is rotated
from clockwise to counterclockwise (past center position). Verify that the count does not increase when the
control is turned from counterclockwise to clockwise.
Change to - SLOPE (button in) and push the RESET
button to clear the display. The readout should now
increase one count each time the CH A LEVEL control is
rotated from counterclockwise to clockwise (past center).
Turning the control from clockwise to counterclockwise
should not increment the display.
OPERATING MODES
GENERAL
The following discussion provides general information
about each mode of operation and instructions on making
measurements for FREQUENCY A, RATIO A/B, TIME
INTERVAL (WIDTH B and TIME A - B), EVENTS A
DURING B, and TOTALIZE.
FREQUENCY A MODE
In this mode the input signal isconnectedto CH A Input
only, either through the rear interface or the front paneI
connector. Use ac coupling for most frequency
measurements to avoid readjusting the LEVEL control
because of changing dc levels. The repetitive nature of the
signals makes slope selection unnecessary for frequency
measurements. Signals less than 3 volts peak-to-peak
need not be attenuated; larger signals should be
attenuated to within the range of 60 mV to 3 V peak-topeak.
Channel B Slope
Set the FUNCTION switch to PERIOD B, CH B to +
SLOPE (button out), and the AVGS/TIMING switch to 1.
Push the RESET button. Check that the GATE indicator
turns on when the CH B LEVEL control is rotated from
clockwise to the counterclockwise position. Turning the
control back to clockwise should have no effect on the
GATE indicator. Another turn from clockwise to
counterclockwise turns the GATE indicator off.
Change to - SLOPE (button in) and press the RESET
button. Observe that rotating the CH B LEVEL control
from counterclockwise to clockwise and back produces
an action that is just opposite that described in the
preceding paragraph.
changes unreasonably, the DC 503A is not being
triggered properly, either because the controls are not
correctly set or the signal is beyond the capabilities of the
counter.
Measurement Intervals. To adjust the trigger controls,
choose a short gate time such as .1 second or .01 seconds.
This gives rapid feedback via the display whether or not
the counter is being triggered. Final selection of gate time
depends upon the frequency being measured, desired
resolution, and willingness of the operator to wait for a
measurement.
Resolution. A 10 second gate time means the operator
must wait 10 seconds for a measurement to be made and
displayed. This will give 0.1 Hz resolution. A 10 second
count will display fewer than the available eight digits for
any signal below 10 MHz.
Set the FUNCTION switch to FREQUENCY A and, with
the AVGS/TIMING switch, select one of the shorter gate
times. Set the DISPLAY TIME control fully counterclockwise. Connect the signal to be measured to the
input and adjust the LEVEL control for a stable display.
The LEVEL control setting should not be critical unless the
signal amplitude and frequency are close to the specified
limits.
If the count varies from reading to reading, it is
probably caused by jitter in the signal source. If the count
Overflow. Through intentional use of “overflow” dis-
plays, it is possible to improve the resolution of the
counter. Select a gate time that displays the most significant digit as far to the left as possible. Note the numbers
displayed to the right of the decimal. Move the decimal to
the left, by selecting longer gate times, until the desired
resolution is achieved. The OVERFLOW indicator will light
when the most significant number overflows the last
storage register. The relationship between gate time,
measured frequency, displayed digits, and overflow is
shown in Table 2-5.
2-7
TM 9-6625-474-14&P-3
GATE TIME
Table 2-5
VS MEASUREMENT RESOLUTION
Measurement Rate. Once a stable measurement is
obtained, the rate at which measurements are made can
be controlled by the DISPLAY TIME control. Turning the
control clockwise holds off the gate and stores the display
for a longer time before a new measurement is made and
displayed. Display time and gate time together complete a
measurement-display cycle.
The DISPLAY TIME control is uncalibrated and
variable from about 0.1 second (in the MIN position) to
about 5 seconds. At the extreme clockwise end of the
control is a detent position called HOLD. In HOLD, the last
count taken will be stored and displayed for an indefinite
period. A new count and display can be initiated by
pressing the RESET button, moving the DISPLAY TIME
control out of the detent, or changing the gate time.
PERIOD MODES
The period and period average modes allow single
period measurements or multiple period averages to be
made with input frequencies into CH B. These modes are
useful for making low frequency measurements where
maximum resolution is desired without waiting for long
measurement time. Simply stated, the PERIOD B mode
reverses the functions of signal and clock as compared to
FREQUENCY A mode. Refer to Fig. 2-4A.
Averaging. Resolution and accuracy is improved by
averaging the signal value over a large number of signal
events. This increases the total time to take a measurement, i.e., similar to selecting a longer gate time in
FREQUENCY A mode. Refer to Fig. 2-4B.
preferred. Other wave shapes can be accurately measured
if the amplitude is kept high.
TIME INTERVAL MODES
Two modes of time interval measurement can be
selected: WIDTH B, and TIME A - B. The WIDTH B mode
measures the time between two points on a waveform,
These two points are selected by the CH B triggering
controls such that the counter main gate turns on at the
point selected by the CH B SLOPE and LEVEL controls,
and turns off at the same level but the opposite slope,
Refer to Fig. 2-4C.
The TIME A - B mode measures the time between two
points on two waveforms. These two points are controlled
such that the CH A triggering controls select the point at
which the main gate turns on, andthe CH B controls select
the point at which the main gate turns off. Refer to Fig. 2-
4D.
Triggering. The voltage levels necessary to establish
the triggering points on any selected slope are monitored
and set with digital voltmeter readings at the CH A/CH B
TRIG LEVEL pin jacks on the front panel or rear interface
connections. Fig. 2-5 illustrates typical TRIG LEVEL
voltage settings for various time interval measurements.
When making these measurements, each channel must be
dc coupled and coaxial cables must be properly terminated in order to maintain signal fidelity.
Low Frequencies. Period Measurements of signals
below 10 Hz, and particularly in the lowest decade from
0.1 Hz to 1.0 Hz, become rather sensitive to wave shape
and amplitude. Since it is desirable for the signals to pass
through the trigger hysteresis abruptly, square waves are
2-8
WIDTH B Mode. In order to measure pulse duration
(Fig. 2-5, waveform 3), the 50% level must be determined.
Set the FUNCTION switch to WIDTH B and the CH B
LEVEL control fully counterclockwise. Apply the input
signal to the CH B input connector. The GATE indicator
must be off.
TM 9-6625-474-14&P-3
Fig. 2-4. Representation of Interval measurements.
Rotate the LEVEL control until the GATE indicator just
come on and record the digital voltmeter reading.
Continue rotating the LEVEL control until the GATE
indicator just goes off and record the digital voltmeter
reading. Subtract the first digital voltmeter reading from
the second and divide by 2; this is the 50% level.
Reset the CH B LEVEL control so that the digital
voltmeter indicates the 50% level. Read the pulse duration
from the DC 503A display.
Time A -
B Mode. This measurement requires input
signals to both CH A and CH B, but the peak-to-peak
signal amplitude should first be determined using the
WIDTH B mode instructions. For TIME A - B
measurements, follow these steps:
1.
Set the FUNCTION switch to WIDTH B.
Referring to WIDTH B mode instructions, determine
2.
the peak-to-peak amplitude and desired triggering
level of the signal to be applied to the Channel B
input.
If the signal to be applied to Channel A input is
3.
different than that being applied to Channel B,
repeat Step 2 for this signal.
4.
Set the Channel B LEVEL control to the desired
triggering level as calculated in Step 2.
5.
Set the FUNCTION switch to TIME A - B.
Set the Channel A LEVEL control to the desired
6.
triggering level as calculated in Step 3.
7.
With signals connected to the proper channels, read
the elapsed time interval between the triggering
level of Channel A and the subsequent triggering
level of Channel B from the DC 503A display.
Time Interval Averaging. Averaging can be used to
increase the accuracy and resolution of repetitive signal
measurements. The basic reason for averaging is the
error is truly random, then as more intervals are averaged,
the measurement will tend to approach the true value of
the time interval. For time interval averaging to work, the
time interval being measured must be repetitive and have a
repetition frequency that is nonsynchronous to the
counter clock rate. The DC 503A will measure up to 10”
averages in both Width B averaging and TIME A - B
averaging.
2-9
TM 9-6625-474-14&P-3
Fig. 2-5. Typical CH A and CH B Level Out voltage settings for various time interval measurements.
EVENTS A DURING B MODE
In the EVENTS A DURING B mode, the events applied
to Channel A are counted. The count is gated by the signal
applied to Channel B input. The accumulated total of
events A that arrived during the time signal B was
triggered is displayed in the readout. Refer to Fig. 2-6.
The following procedure can be used to make a
measurement like that shown in Fig. 2-6.
1. Apply the signal to be counted to Channel A. With
the FUNCTION switch at FREQUENCY A, set
Channel A SLOPE switch to + SLOPE. Adjust the
LEVEL control for a stable display.
2. Apply the control signal to Channel B. With the
FUNCTION switch at PERIOD B, set Channel B
SLOPE switch to + SLOPE, Adjust the LEVEL
control for a stable display.
3. Set the FUNCTION switch to EVENTS A DURING B.
When the Channel B signal excursion occurs, Channel
B is triggered andthe gate opens, allowing the Channel A
pulses to be counted.
Averaging. Averaging can be used to Increase the
accuracy and resolution of repetitive event per interval
measurements. As more events are averaged, the
measurement tends to approach the true value of the
number of events per interval.
RATlO MODE
The DC 503A may be used to measure the ratio of two
signals, where one signal is applied to Channel A input
and the other signal is applied to Channel B input.
2-10
TM 9-6625-474-14&P-3
Fig. 2-6. Illustration of CH A events counted from portion of CH A signal pulses during the counter gate open time (controlled by
CH B signal).
In the Ratio A/B mode, the frequency of the signal
applied to Channel A is divided by the frequency of the
signal applied to Channel B, and the resultant ratio is
displayed.
measurements, the smallest number of averages that
produces a useful number of digits should be considered.
TIME MANUAL MODE
This mode is a manual analog of the TIME A - B mode.
Triggering. The operation of Channel A and Channel B
trigger controls is the same as for frequency and period
measurements. Set the trigger controls as follows:
1.
Go to the FREQUENCY A mode and adjust the
Channel A trigger controls for a normal frequency
measurement.
Go to the PERIOD B mode and adjust the Channel B
2.
trigger controls for a normal period measurement.
Leaving the Channel A and Channel B trigger
3.
controls as they are, gotothe RATIO A/B mode. The
correct ratio should be displayed.
Resolution. The AVGS/TIMING switch, which controls
the number of averages of the Channel B signal, may now
be set to display maximum resolution. For most
In this mode, only the AVGS/TIMING switch and
START/STOP switch affect the display.
Starting and Stopping. The TIME MANUAL mode may
bethought of as a “stop-watch” type of operation. With the
FUNCTION switch inthe TIME MANUALposition (and the
internal jumper properly positioned), the display starts
counting time-base pulses when the START/STOP switch
is depressed. It will continue to count and display the
accumulated total until the START/STOP switch is released. The last count will then be held in the display until
another START command is given (in which case the
count will again advance), or other controls are actuated.
Pressing the RESET button will return the display to zero.
Changing the setting of the AVGS/TIMING switch will
change the frequency of the time-base pulses being
counted and reset the display to zero. The start/stop
function can also be performed remotely via the rear
interface connections.
2-11
TM 9-6625-474-14&P-3
Clocking Rate. When the AVGS/TIMING switch is in
the 1 s position, one-second pulses are being counted and
the display accumulation advances one count per second,
and so on.
Whenever the accumulated count is above 99,999,999,
the OVERFLOW indicator will light to indicate register
overflow; however, the accumulation continues at the
not displayed.
TOTALIZE A MODE
This mode is a manual analog of the FREQUENCY A
mode. lnthismode, signal event sapplied tothe Channel A
input are counted and the accumulated total displayed
during the time the START/STOP button is depressed to
the START position. The main application of this mode is
to accumulate the count of relatively infrequent and
irregular events.
Operation. Apply the signal to Channel A input and set
the trigger controls the same as for a frequency measurement. Only the Channel A trigger controls, the RESET
button, and the START/STOP button affect the display in
this mode.
Starting the Count. Press the START/STOP button and
adjust the Channel A LEVEL control until a count begins to
advance. The accumulated count is displayed in whole
numbers.
will continue to be displayed. No more incoming events
will be added to the total.
Restarting and Resetting. When the START/STOP
button is again depressed, incoming events will advance
the displayed total. Resetting the count to zero can be
done at any time by pressing the RESET button.
Remote start/stop. Starting and stopping the count can
be accomplished remotely via connections to the rear
interface.
REPACKAGING FOR SHIPMENT
If the Tektronix instrument is to be shipped to a
Tektronix Service Center for service or repair, attach a tag
showing: owner (with address) and the name of an
individual at your firm that can be contacted. Include
complete instrument serial number and a description of
the service required.
If the original package is not fit for use or not available,
repackage the instrument as follows:
Surround the instrument with polyethylene sheeting, or
other suitable material, to protect the exterior finish.
Obtain a carton of corrugated cardboard of adequate
strength and having inside dimensions no Iess than six
inches more than the instrument dimensions. Cushion
the instrument by tightly packing dunnageor urethane
foam between the carton and the instrument,
sides, Seal the carton with shipping tape or
dustrial stapler.
on all
an in-
Stopping the Count. If the START/STOP button is
released and no other controls are actuated, the last total
2-12
The carton test strength for your instrument
pounds.
is 200
SECTION 3
TM 9-6625-474-14&P-3
THEORY
OF OPERATION
BLOCK DIAGRAM DESCRIPTION
Introduction
For the following block diagram description refer to the
Block Diagram foldout page at the rear of this manual.
Channel A and Channel B Amplifiers
There are two inputs, CH A and CH B. Signals to be
counted or timed are applied to either or both channels via
front panel bnc connectors or via the rear interface. The
front panel inputs for both channels are terminated with an
paralleled with approximately 27 pF. The rear interface
inputs to both channels are terminated with a resistance of
Signal Flouting circuits.
Each channel contains an ac/dc coupling switch, a X1
or X5 attenuation network, a buffer amplifier circuit acting
as a comparator that compares the incoming signal level
against the triggering level as a reference, and
amplifier/Schmitt circuits driving the signal slope selec-
tion functions in the Signal Routing circuits. Each channel
also contains an operational amplifier serving as a X1
buffer circuit, supplying a buffered version of the trigger
level at the front panel tip jacks or rear interface connec-
tions.
NOTE
panel with the proper decimal point location and correct
annunciator illuminated.
The Measurement Cycle Timing circuit determines the
Display Time, clears the Gate Generator circuits, loads
(latches) the decade counters, and resets the counters for
the next measurement cycle in all modes of operation.
PERIOD B (Variable Clock)
In this TIMING mode, the CH B signal is passed
through the Signal Routing circuits to the Gate Generator
Input of the Decade Accumulators and the Measurement
Gate is generated by a single period of the signal from
Channel B. As before, the accumulated count for this
mode and all subsequent modes is latched, decoded from
BCD data to 7-segment information, and displayed on the
front panel with the correct annunciator illuminated and
the proper decimal point location.
PERIOD B (Averageable—100 ns Clock)
For this AVGS mode, the Time Base signal
(10 MHz = 100 ns) is not divided; it is applied through the
Signal Routing circuits directly to the Count Input of the
Decade Accumulators. The CH B signal is routed to the
The remainder of this block diagram description
discusses the signal paths through the remaining
circuit blocks and the typical events related to each
mode of operation (FUNCTION) listed on the front
panel.
FREQUENCY A (Variable Gate)
For this mode of operation the CH A signal passes
directly through the Signal Routing circuits to the Decade
Accumulators. The signal is counted by the 1st DCU, then
the 2nd DCU, and then by the 6-Decade Counter (a total of
eight decades). In the FREQUENCY A mode the Time
generate a Measurement Gate (via the Gate Generator) for
the desired measurement time. At the end of the Measure-
ment Gate interval, the accumulated count is latched in
the 8-Decade Latch/Multiplexer circuits, converted from
BCD to 7-segment information and displayed on the front
of the CH B signal. The Time Base is counted for 10”
periods before the accumulated count is latched for
display.
WIDTH B (Variable Clock)
In this TIMING mode, the 10 MHz Time Base is routed
routed directly to the Count Input of the Decade Accumulators. The CH B signal is used to generate the
Measurement Gate (via the Gate Generator). A single
pulse width at the output of the Channel B amplifier
generates the gate.
WIDTH B (Averageable—lOO ns Clock)
In WIDTH B, AVGS mode, the Time Base signal is not
divided by N; it is routei directly to the Count Input of the
3-1
TM 9-6625-474-14&P-3
Counts are accumulated in the decade counters during
either the positive portions of the pulse widths or the
negative portions, dependent on the SLOPE polarity
selection for the Channel B signal.
signals and the Channel A signals are counted during that
time.
TOTALIZE A
In the TOTALIZE A mode the Measurement Gate is
generated by the START/STOP switch on the front panel
or via the Remote Start/Stop line at the rear interface. The
Circuit, and Gate Generator circuits are not used for this
mode. Instead of accumulating clock signals from the
signals are accumulated during the START/STOP interval.
TIME MANUAL (Variable Clock)
For this mode there are no inputs to Channel A or
Circuit whose output is routed directly to the Count Input
of the Decade Accumulators. The Measurement Gate
interval is generated either by using the START/STOP
switch on the front panel or by changing the voltage level
on the Remote Start/Stop input at the rear interface.
EVENTS A DURING B (Averageable)
This mode is exactly like the WIDTH B (Averageable)
mode, except that the output of the Time Base is disabled
and the output of Channel A is applied directly to the
Count Input of the Decade Accumulators. For this mode,
the pulse width at the output of Channel B is routed to the
produce the Measurement Gate Interval. The Channel A
events are averaged for 10” pulse widths from Channel B.
RATIO A/B (Averageable)
Decade Accumulators, 6-Decade Counter/8Decade Latch
The 1st DCU consists of ECL flip-flops, requiring
ECL/TTL conversion to drive the first decade latch The
2nd DCU operates at TTL levels and drives the second
decade latch directly. From that point, there are six more
internal counters and six more decades of latch, all
contained in one integrated circuit. This arrangement
provides a total of eight decades of count and eight
decades of latch.
The 6-Decade Counter/8-Decade Latch circuit has its
own internal oscillator to generate the Time Slot information. It also generates the Scan Clock, Overflow, and BCD
output data. Between the time slots and BCD data there is
enough information to drive the Display. The zero blanking function is also provided internally.
Measurement Cycle Timing
The display timing, reset, clear, and load (latch)
functions for the decade counters are provided by the
Measurement Cycle Timing circuit.
Decimal Point and Annunciator Encoder
The Time Base output is disabled and not used for this
mode; Channel A signals are routed directly to the Count
3-2
The decimal point location is determined by encoding
circuits using the time slot information and information
Loading...