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TEKTRONIX
D IVI 502
DIGITAL
IVI U LT I IVI ET E R
INSTRUCTION MANUAL
Tektronix, Inc .
P.O . Box 500
Beaverton, Oregon 97005 Serial Number
First Printing Aug 1974
070-1726-00
WARRANTY
All TEKTRONIX instruments are warranted against
defective materials and workmanship for one year .
Any questions with respect to the warranty should
be taken up with your TEKTRONIX Field Engineer or
representative .
All requests for repairs and replacement parts
should be directed to the TEKTRONIX Field Office
or representative in your area . This will assure you
the fastest possible service . Please include the
instrument Type Number or Part Number and Serial
Number with all requests for parts or service .
Specifications and price change privileges reserved .
Copyright ' 1974 by Tektronix, Inc., Beaverton,
Oregon . Printed in the United States of America . All
rights reserved . Contents of this publication may not
be reproduced in any form without permission of
Tektronix, Inc .
U.S .A . and foreign TEKTRONIX products covered
by U.S. and foreign patents and/or patents pending .
TEKTRONIX is a registered trademark of Tektronix,
Inc .
DM 502
TABLE
OF CONTENTS
Page
SECTION 1 OPERATING INSTRUCTIONS
Introduction 1-1
Instrument Description 1-1
Installation and Removal 1-1
Operating Considerations 1-2
Input Connections 1-2
Function's Available at Rear Connector 1-2
Sine Wave Response 1-3
Temperature Measurements 1-3
Making Measurements 1-4
DC Voltage Measurements 1-4
DC Current Measurements 1-4
AC Voltage, Current and Resistance Measurements 1-5
Decibel Measurements 1-5
Temperature Measurements 1-5
Using a Transistor as a Temperature-Sensing Device 1-5
Accurate Current Source 1-6
Specifications 1-6
SECTION 2 THEORY OF OPERATION
Introduction 2-1
Attenuator and Input Switching 2-1
AC Converter 2-1
DB Converter 2-1
Ohms Converter 2-2
Temperature Measurement Circuitry 2-2
Clock 2-3
Analog-To-Digital Converter 2-3
Display 2-5
Power Supplies 2-5
SECTION 3 ELECTRICAL REPLACEABLE PARTS LIST
SECTION 4 SERVICE INFORMATION
Internal Adjustment Procedure
Rear Interface Connector Assignments
Rear Interface Connector Wire Locations
Front Panel Controls and Connectors
Block Diagram
Parts Location Grid
Attenuators and Conversion Circuits Schematic
Integrator, A/D Converter and Display Schematic
Power Supply and Switch Logic Schematic
SECTION 5 MECHANICAL REPLACEABLE PARTS LIST
Accessories
Repackaging
Exploded View
CHANGE INFORMATION
REV . A, OCT. 1974
RA 502 nalm mn'
Section 1-113M 502
OPERATING
INSTRUCTIONS
INTRODUCTION
Instrument Description Interlaced bcd output (1, 3, 2, 4) referenced to the low
The DM 502 Digital Multimeter measures do and ac input, is available at the rear interface connector if user
voltage and current, dBm, dBV, resistance and wired.
temperature. The ac functions are average responding
and rms calibrated for sine waves. A single front panel
control selects all ranges . A front-panel pushbutton
selects dB readout of ac functions in lieu of voltage or NOTE
current. Rear interface-connector input is also pushbut- The DM 502 is not directly compatible with the 153
ton selected from the front panel . Values of dB are Calculator Interface .
obtained by adding the selected dB range value to the
display reading. Readout in dBm or dBV is chosen by an
internal jumper . The unit is shipped with the jumper in the
dBm position .
The maximum input voltage is 1 kV, 350 V at the rear
connectors . The front-panel HI and LO connectors maybe
floated 1 kV maximum aboveground, the rear inputs 350V.
An internal jumper also permits selection of fet input (>
1000 Mil) or 10 Mil input impedance on the two lowest dc-
voltage ranges . The unit is shipped with the jumper in the Installation and Removal
10 Mil position . See Fig . 1-2 . The DM 502 is calibrated and ready for use when
received . It operates in any compartment of a TM 500
series power module . See the power module instruction
manual for line voltage requirements and power module
operation . Fig. 1-1 shows the DM 502 installation and
Temperature measurements are made using a removal procedure.
Tektronix P6430 probe (Tektronix Part Number 010-6430-
00) or other suitable sensing devices. Option 2 in-
struments delete the temperature measuring capability .
Turn the Power Module off before inserting the DM
502. Otherwise, arcing may occur at the rear inter-
face connectors, reducing their useful life and
damage may be done to the plug-in circuitry.
The readout is a 3-1/2 digit display using seven-
segment LED's. The decimal point is automatically Check that the DM 502 is fully inserted in the Power
positioned by the range-function switch . Polarity indica- Module . Pull the PWR switch on the Power Module . One or
tion is automatic. A usable 50% overrange exists in all more characters in the LED display should now be visible.
measurement modes except ac voltage and current, 1000
V dc, and the 2 A do current range. In overrange, the
display blinks and the most significant digit is suppressed .
Upon exceeding the available 50% overrange, a 1 appears The Controls, Connectors and Adjustments foldout
in the most significant digit position . Display readings are page in Section 3 gives a complete description of the front
invalid beyond this point. panel.
REV . A, OCT . 1974
Operating Instructions-DIM 502
Fig . 1-1 . DM 502 Installation and removal .
OPERATING
CONSIDERATIONS
Input Connections interface connector . The Rear Interface Connector
Assignments page in the Service Section at the rear of this
Three binding posts provide measurement connec-
manual gives data on the various connections . Only the
tions. The HI and LO posts are normally used for all
Temp Out, Temp Gnd and HI and LO inputs are factory-
measurements except temperature. Normal measurement
wired . Jumper holes are provided for making the desired
conditions will be with the LO terminal ungrounded . A
bcd output connections . See the wire locations illustration
connection between the LO and GND posts may be made
in the foldout pages for the correct circuit board locations.
to reference the input against DM 502 chassis ground . Use
Simply insert and solder an insulated wire strap in the
caution, as the LO terminal is then connected to earth
proper locations . Buffers are required before the data
ground through the three-wire powercord. False readings
outputs are used to drive external loads . See Fig . 1-3 for a
may be obtained due to ground loops.
typical buffer circuit .
If the INPUT button is pushed in, signal inputs are made
via the rear interface connector ; if the button is out, signal
inputs are made via the front panel.
The DM 502 has a slot between pins 17 and 18 . A barrier
in the corresponding position of the power module jack
allows only compatible plug-ins to be used in that
compartment . This protects the plug-in, should specializ-
Functions Available at Rear Connector ed connections be made to that compartment . Consult the
HI, LO, GROUND, temperature output at 10 mV per Building A System section of the power module manual
degree and bcd connections are available at the rear for further information .
Operating Instructions-DM 502
FET input
jumper position
Connect jumper on
reverse side of board
as shown to hard wire in