Heathkit IM 5225 Manual

Page 1

Heathkit® Manual

for the

FET MULTIMETER

Model lM-5225

595-1 934

52% m6 5M M07

WARNING: TO PREVENT FIRE on SHOCK

HAZARD. DO NOT EXPOSE THIS INSTRUMENT T0 RAIN
OR MOISTURE

HEATH COMPANY
BENTON HARBOR, MICHIGAN 49022

Copyright © 1971

Heath Company

All Rights Reserved

Primed In The United States of Ameflca

Page 2

Page 2

fiiflfifllixszyrrircxxw
TABLE OF CONTENTS
PARTS LIST .................................. 3 Preliminary Checks ....................... 61
Troubleshooting chart ...................... 62
ASSEMBLY NOTES ......................... 8 DC Voltmeter Circuit ........................ 70
AC Voltmeter Circuit ......................... 72
STEP-BY-STEP ASSEMBLY Ohmmeter Tests ............................. 73
Main Circuit Board ........................ 10 Voltage Tests ....................... . 73
Rotary Switch .......................... 19 Operational Troubleshooting ......... . . . . 77
Harness ................................ 23 DC and AC Milliammeter Circuit .............. 79
Assembly Check List . . .................. 30
FrontPanel ........... ... 31
Cabinet Bottom ............................ 36
Test Lead Assembly ........................ 42 SPECIFICATIONS ............................ 30
INITIAL TESTS .............................. 43 CIRCUIT DESCRIPTION ...................... 84
CALIBRATION .............................. 45 SEMICONDUCTOR IDENTIFICATION
CHART ..................................... 89
FINAL ASSEMBLY .......................... 51
SCHEMATIC ............................ Fold-in
OPERATION ................................ 52
CIRCUIT BOARD X-RAY
MAINTENANCE ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 53 VIEW ....................... Illustration Booklet
IN CASE OF DIFFICULTY Warranty ..................... Inside Front Cover
Troubleshooting Information ................ 59
Basic Meter Tests .......................... 61 Customer Service .............. Inside Rear Cover

Page 8

Page 8
-HEATHKIT9

ASSEMBLY NOTES

TOOLS

You will need these tools to assemble your kit.

PHILLIPS

. OTHER HELPFUL
l TOOLS {D

F'LIERS /

PUERS DIAGUNAL
cunns

STRIPPERS

DESOLDERING
BULB

SCREWDRIVER
II8"&1I4"-BLADE
SCREWDRIVERS

HEMHKIT
SOLDERING
IRON

' PENCIL
NU, SHIRT DESOLDERING
Mot SOLDERINGIRON
IIMAVWBIETSUKPlfiliIED DRIVERS I25 IORUWAUSI
I
I
l O REMOVE SOLDER FROM CIRCUIT CONNECIIONS, J
ASSEMBLY
1. Follow the instructions carefully and read the Most kits use a separate Illustration Booklet"
entire step before you perform the operation that contains illustrations (Pictorials, Details,
etc.) that are too large for the Assembly Manual.
2. The illustrations in the Manual are called Keep the Illustration Booklet with the As-

Pictorials and Details. Pictorials show the over-
all operation for a group of assembly steps;
Details generally illustrate a single step. When
you are directed to refer to a certain Pictorial
for the following steps," continue using that
Pictorial until you are referred to another Picto~
rial for another group of steps.

sembly Manual. The illustrations in it are ar-
ranged in Pictorial number sequence.

Position all parts as shown in the Pictorials.

Solder a part or a group of parts only when you
are instructed to do so.

Page 17

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_HEATHKITC"

m-

[ ] C105: 433 pF mica.

( ] C104: 20 pF mica.

[ ) C102: 36 pF mica.

( ) C106:4900 pF [.0049] mm.

NOTE: When you install ceramic
capacitors, remove any excess coat-
ing from the leads: Use long-nose
pliers to remove this coating.

REMOVE COATING
EVEN WITH /
BOTTOM OF

CAPACITOR BODY

l

C101: 5000 pF (.005) 1.4 kV
ceramic.

C111: .1 F Mylar.

[ ) C109: .44 F film.

( 1 C125. FB4, FBS: 470 pF ceramic
with a small ferrite head on each
lead.

SMALL ,:_:
FERRITE BEAD ll

Solder the leads to the foil and
cut off the excess lead lengths.

[ 1 C116: 1000 pF (.001) ceramic.

( ] C123: .1 11F ceramic.

( ) C117: .1 [JP Mylar.

[ ] C118: .1 11F Mylar.

( ) C119: .1 14F Mylar.

( ) C121: 10 pF ceramic.

( ] C122: .1 p.17 ceramic.

C124: .1 MP ceramic.

c115: 1000 pF (.001) ceramic. PICTORIAL 1-7

Solder the leads to the foil and
cut off the excess lead lengths.

Page 32

Page 32

6-32 PUSH-ON ( ]
K NUT

FOAM METER
TAPE BRACKET
( ]
Ilka? ( l
l":\FLAT
V SIDE
Detail4-1C ( l

[ ) Refer to Detail 4-1C and install 6-32 push-on
nuts at the indicated holes in ameter bracket. Be
sure the flat side of each nut is positioned as
shown.

-HEATHKIT

Cut four 3/4 long pieces from the length of
foam tape.

Refer to Detail 4-1C and remove the protective
backing from two pieces of the foam tape. Then
press them onto the meter bracket at the indi-
cated locations.

In the same manner, prepare the other meter
bracket.

M1: Refer to Detail 4-1D and fit the meter into its
hole in the front panel. Push the meter as far as
possible in the direction of the large arrow.

Refer to Detail 4-1D and secure the meter in the
front panel with the two meter brackets. Use
two 6-32 X 5/ 16" flat-head screws in each meter
bracket. Press the brackets against the meter to
hold the meterfirmly in place in the front panel
before you tighten the screws.

6-32x5/16
FLAT-HEAD
SCREW 1
W_\ ll
METER 8>
Ml -
METER
BRACKET
METER PANEL \/
BRACKET
Detail 4-1D
0 % 1/2 3/. 1 (INCHES) 2 3 4 5 6 7
l"I3|5"I7iBl I ill i.J | 1 l Ihl I l l_.I l I I AL I l | l
Iv'uvuvI I I'I I Iml W'III I I'T I I'
D 5 I (CM: 2 3 4 s 5 7 e 9 yo I» 2 V1! 14 15 6 11

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Page 52

OPERATION

Refer to Pictorial 11-1 [Illustration Booklet, Page 6) for
a description of the control and input functions.

DUTY CYCLE

Since the power consumption of the Multimeter is
very low, you may wish to leave the instrument on
continuously during the daily work period. Always
allow a 30 minute warm-up period from a cold start to
insure best accuracy. However, the Multimeter will
provide serviceable accuracy at turn-on.

SAFETY PRECAUTIONS

You may often use your Multimeter to check, main-
tain, and repair electronic equipment which contains
DANGEROUSLY HIGH VOLTACES. Because of this
danger, you should always observe the safety proce-
dures listed below.

1. Always handle the test probe by the insulated
housing only. Be careful not to touch the ex-
posed tip.

2. When you measure high voltages, turn off the
power to the equipment to be tested before you
connect the test leads. If this is not possible. be
very careful to avoid accidental contact with any
object that could provide a ground return [cir-
cuit completion] path.

3. If it is at all possible, use only one hand when
you test energized equipment. Keep one hand in
your pocket or behind yourback to minimize the
possibility of accidental shock.

4. If possible, insulate yourself from ground while
making measurements. Stand on a properly in-
sulated floor or floor covering.

5. Before you connect the test leads for a resistance
measurement, turn off the power to the equip-
ment to be tested, and discharge any capacitors
which may have stored a charge.

_HEATHKIT~>

EXTERNAL INTERFERENCE

Stray AC and RF (radio frequency] fields that affect
measurements, can usually be reduced or eliminated
by one of the following:

A. Usetwisted and as short as possible input leads.

B. Use inner»wire shielded cable for input leads.
Connect the shield to the rear panel [earth]
ground screw.

C. For voltage measurements, a 10 k!) to 1 M0
resistor can be connected across the input ter»
minals. However. this may tend to load high
impedance circuits.

READING THE METER

This section of the Manual will familiarize you with
the meter scales. Instructions are given for reading
each scale.

AC or DC Voltage Readings

NOTE: The numbers in the Volts" bracket on the
Range switch refer to the full-scale voltages of the
Multimeter.

.1 VOLT RANGE - Read the O-to-l scale and move
the decimal point one place to the left. For example, a
reading of .7 on this range would indicate a measure-
ment of .07 volts, as shown in Pictorial 11-2.

0M5 7 345°\ 5") l5?
.

o '1 3 L1 is
\ \
o y/A?
\/ \
o ATTYTT
O (333040-6744 0
DC -

0.1 VOLT RANGE INDtCATING 0.07v
PICTORIAL 11-2

.3 VOLTAGE RANGE - Read the 0»to»3 scale and
move the decimal point one place to the left. For
example, a reading of 2 would indicate a measure.
ment of .2 volts.

Page 56

Page 56

AC VOLTAGE INTERPRETATION

Your Meter can measure almost any type of AC vol-
tage. Filament voltage, power line voltage, noise vol-
tage, or even output or gain measurements can be
made quickly and accurately. It is important, hOW<
ever, to understand how the various types of input
waveforms affect the readings and how to interpret
these readings for greatest accuracy. For this reason,
the following information is presented.

When a DC voltage is applied to a resistor, it produces
a measurable temperature increase. If an AC voltage is
applied to the same resistor and produces the same
temperature increase, then the AC voltage must be
producing the same amount of power. Since this
power produced by the AC voltage is averaged over a
period oftime, it is called mean (or average) power.
The AC voltage that produces this power is propor-
tional to the square root of the mean power, and is
called the rms [root-mean-square) voltage. AC meters
are usually calibrated in ms voltage. For a sine wave
[see Pictorial 11-5A], the most common AC voltage
waveform. the rms value of each half cycle is .707
times the peak of the waveform.

PEAK

c
o OMELiX. lvl_V_E___. PEAK

OSQUARE WAVE
___________ PEAK AND RMS
:TW

PICTORIAL 1 1-5

The following relationships exist for sine wave AC
voltages:

rms voltage = peak Voltage x 0.707

Peak voltage = rms X 1,414

Peak-to-Peak voltage = rms X 2.828

rms voltage = peak-to-peak voltage x 0.3535

If the input voltage to your Multimeter is an AC sine
wave, both the positive and negative portions of the
signal will deflect the meter needle upscale.* Since
the meter movement has mechanical inertia, it aver-
ages the current pulses and causes the meter needle
to indicate this average value. Therefore, the scales
are designed to indicate the rms value of a sine wave
while the meter itself is actually responding to the
average value of each portion of the waveform.

Ifa nonsinusoidal (not a sine wave] waveform such as
a square wave, sawtooth wave, or pulse is being mea-
sured, the indicated reading on the scale must be
given some special interpretation. For example, the
complex waveform shown in Pictorial 1 1-5B contains
a spike [peak] that may be several times as large as
the average value of the waveform. Since the spike is
of such short duration, the average value of the overall
waveform is barely affected. On the other hand, the
symmetrical square wave (a square wave having posi-
tive and negative portions of equal amplitude and
time duration] shown in Pictorial 11-5C would indi-
cate an rms value higher than its peak value, On your
Multimeter, a symmetrical square wave having a
1.0-volt peak would indicate 1.10 volts.

Remember: Examine any nonsinusoidal waveform,
with an oscilloscope or a true rms meter if you want a
highly accurate measurement.

See the Basic Meter Circuit portion of the Circuit
Description.

Page 83

-HEATHKIT -

GENERAL

Meter ......................................

Input Overload Protection ....................

Front Panel Controls .........................

Meter Temperature Coefficient ................

Operating Temperature ......................
Storage Temperature .........................

Dimensions (Overall) ........................

Weight .....................................

Page 83

4-1/2, 200 A loo-degree movement.

Will sustain 700 VAC (1000 VPK) or
1000 VDC on 1-volt to 1000-volt ranges.
Will sustain 220 VAC or 300 VDC on any
other range.

2-ampere. quick-blow input fuse caused
to open with overload on 0. X 1 range,
to Q X 1k range, and 0.01 to 1000 m
ranges by input clamping diodes.
Measurement circuitry on 0.1 volt and
0.3 volt ranges protected by

clamping transistors.

24~position, continuous-rotation
Range switch with concentric ohmmeter
full-scale adjustment control.

4-position pushbutton switch: AC.
DC/Q, QLV. Power (On/Off).

Maximum of 10.1% or 10.1 degrees of
arc [whichever applies) per degree

C over a range of 10 to 40 degrees

c (50° to 104°F).

0 to 50 degrees C [32° to 122°F].

-40 to +70 degrees C (-40° to +158°F].

5-3/4 wide X 6-7/8 high X 11-1/4" deep
[14.61 X 17.46 X 28.56 cm).

5-3/4 pounds [2.61 kg).

The Heath Company reserves the right to discontinue
products and to change specifications at any time
without incurring any obligation to incorporate new
features in products previously sold.