Hameg HM 203-7 User manual

Instruments
MANUAL
Oscilloscope
HM 203-7

Table of contents
Oscilloscope datasheet
with technical details . P 1
Accessories .Z 1
Operating Instructions
General Information .Ml
Use of tilt handle. Ml
Safety.Ml
Operating conditions.M2
Guarantee .M2
Maintenance.M2
Switching over the mains/line voltage.M2
Type of the signal voltage .M3
Amplitude Measurement.M3
Time Measurements.M 4
Connection of Test Signal .M 6
First Time Operation.M 7
Trace Rotation. M 7
Probe compensation and use. M 7
1 kHz compensation.M 8
1 MHz compensation.M 8
Operating modes of the vertical amplifiers .... M 8
X-Y Operation. M 9
Phase difference measurement in DUAL mode . M 9
Measurement of an amplitude modulation .... M10
Triggering and time base.M10
Automatic Triggering.M10
Normal Triggering, Slope.Mil
Trigger coupling. Mil
Alternate Triggering.Ml 2
Line Triggering.Ml 2
Triggering of video signals.Ml 2
External triggering, Trigger indicator.Ml3
Holdoff-time adjustment.Ml 3
Component Tester.Ml 3
Test patterns.Ml 6
Short instruction K 1
Front panel elements
Folder with front view .K 2
Test Instructions
General.T 1
Cathode-Ray Tube; Brightness and Focus,
Linearity, Raster Distortions.T 1
Astigmatism Check.T 1
Symmetry and Drift of the Vertical Amplifier . . . . T 1
Calibration of the Vertical Amplifier.T 1
Transmission Performance (Vertical Amplifier) . . . T 2
Operating Modes: CH I/ll, DUAL, ADD, CHOP.,
INVERT and X-Y Operation.T 2
Triggering Checks .T 3
Timebase.T 3
Holdofftime .T 4
Component Tester.T 4
Trace Alignment.T 4
Mains/Line Voltage Checks.T 4
Oscilloscope
HM 203-7
Service Instructions
General.SI
Instrument Case Removal.SI
Operating Voltages.SI
Maximum and Minimum Brightness.SI
Astigmatism control.S 2
Trigger Threshold.S 2
Trouble-Shooting the Instrument.S 2
Replacement of Components and Parts.S3
Replacementof the Power Transformer.S3
Adjustments.S3
Circuit Diagrams
Wiring Diagram.D 1
Identification of electrical components.D 2
Y-Inputs, Attenuators,
Preamplifier Channel I and Channel II.D 3
Y Intermediate Amplifier Channel I and Channel II
Channel Selection, Component Tester.D 4
Trigger Circuit, TV Sync Separator, Calibrator. . . .D 5
X and Y Final Amplifier.D6
Timebase Circuit, Trigger Control.D 7
CRT Circuit, Unblanking .D 8
Power Supply.D 9
Component Locations EY Board.DIO
Component Locations CO (IF) Board.DIO
Component LocationsXY Board.Dll
Component Locations TB Board.D12
Subject to change without notice
5.91 • 203-7

OSCILLOSCOPE HM 203-7
Specification ( 21 ° C; ismin.)
Vertical Deflection
Operating modes; Channel I orCh. II separate,
Channel I and II: alternate or chopped;
(Chopper frequency approx. 0.4 MHz).
Sum or difference of Ch. I and Ch. II.
(channel II invertible).
X-Y Mode: via Channel I and Channel II.
Frequency range: 2x DC to 20MH2 (-3dB).
Risetime: approx. 17.5ns. Overshoot: ^1 %.
Deflection coefficients: 10 calibrated steps
from 5mV/div. to 5V/div in 1-2-5 sequence.
Accuracy in calibrated position: ±3%.
Variable 2.5:1 to max, 12.5V/div.
Y-magnification x5 (calibrated) to 1 mV/div. ±5%
(frequency range DC to 3.5MHz, —3dB)
Input impedance: 1 MQ II 25pF.
Input coupling: DC-AC-GD (Ground)
Input voltage: max. 400V (DC + peak AC).
Y-output from Ch. I or Ch. II (optional)
Trigger System
With automatic; 10Hz-40MHz. >0.5div.
normal with level control from DC-40MHz.
Slope: positive or negative.
ALT. triggering ; LED indication for trigger action.
Sources: Ch. I, Ch. II, line, external.
Coupling: AC (S10Hz -10 MHz), DC (0 -10 MHz),
LF (0 - <50kHz), HF (>1,5kHz • 40MHz).
Threshold external >0.3V.
Active TV-Sync-Separator for line and frame.
Horizontal Deflection
Time coefficients: 18 calibrated steps
from 0.2|is/div. to 0.1 s/div. in 1-2-5 sequence,
accuracy in calibrated position: ±3%.
variable 2.5:1 to max. 0.25s/div.,
with X-Magnifier x10 (± 5%) to == 20ns/div..
Hold-Off time: variable to approx. 10:1.
Bandwidth X-Amplifier: DC-3 MHz (-3dB).
Input X-Amplifier via Channel II,
sensitivity see Ch. II specification.
X-Y phase shift: <3° below 220kHz.
Z input (optional)
Component Tester
Test voltage: approx. 8.5Vm,5 (open circuit).
Test current: approx. 8mA,(shorted).
Test frequency: ^ line frequency.
Test connection: 2 banana jacks 4mm 0.
One test lead is grounded (Safety Earth).
General Information
Cathode-ray tube: D14-364 P43/123, or ER151 -GH/-,
rectangular screen, intern, graticule. 8x10cm
Acceleration voltage: 2000V,
Trace rotation: adjustable on front panel.
Calibrator: square-wave generator == 1 kHz for
probe compensation. Output: 0.2Vand2V +1 %.
Line voltage: 110, 125, 220, 240 V~ ±10%.
Line frequency: 50Hz to 400Hz.
Power consumption : = 37 Watt (at 50 Hz).
Max. ambient temperature: -(-10°C...-T40°C.
Protective system: Safety Class I (lEC 348).
Weight: approx. 7.5kg. Colour: techno-brown.
Cabinet: W 285, H 145, D 380mm.
Lockable tilt handle.
20 MHz Standard Oscilloscope
2 Channels, max. 1 mV/div. sensitivity; Component Tester
Timebase: 0,1s/div. to 20ns/div.; Variable Holdoff; Alternate Triggering;
Triggering: DC-40MHz; TV Sync Separator; Trigger LED
The HM 203-7 is Western Europe's best selling oscilloscope because it
responds thoroughly to customer demands for reliability, superior perfor¬
mance, and ease of operation.
The outstanding transient response of the HM 203-7, particularly when
displaying square wave signals, is one of the pre-eminent features of this quality
instrument, the integrity of the signals reproduced by this oscilloscope reflect a
dedication to engineering excellence normally only found in expensive labora¬
tory instruments. As an aid to ensure the correct polarities when displaying the
sum, difference, or video signals, an "invert" control is provided on channel II.
Technically advanced triggering circuits enable the user to attain clear, stable
displays from DC to over 40 MHz, with input levels as low as 0.5 divisions. The
Holdoff control enables even complex asynchronous waveforms to be solidly
displayed. Trigger action is indicated by an LED, which illuminates whenever the
trigger threshold point is crossed. And for the display of video signals, the
HM 203-7 has a low distortion active TV sync separator, which allows for auto¬
matic synchronizing with line and frame frequencies. "Alternate triggering"
mode enables the display of two asynchronous signals simulteneously.
The CRT's 8x10 cm internal graticule enhances parallax-free viewing over a
wide field. In addition, the CRT is fully shielded with mumetal to prevent display
distortion in the presence of magnetic fields.
As a practical, built-in feature, the component tester enables the operator
to quickly identify faulty semiconductors and a large variety of individual compo¬
nents, both in circuit and out.
The HM203-7 was specifically designed for use in production lines, general
service applications, and for technical training facilities. The multiplicity of display
modes, the easy-to-understand front panel, and the operational simplicity of the
HM203-7 make it also an ideal training scope for educational purposes.
Accessories supplied
Two 10:1 probes. Line cord. Operators Manual.
Subject to change without notice.

OSCILLOSCOPE ACCESSORIES
Test Cable Banana-BNC HZ32
Coaxial test cable; length 1.15m, characteristic impedance 50fl.
Cable capacitance 120pF. Input voltage max. 500Vp.
Test Cable BNC - BNC HZ34
Coaxial test cable; length 1 m, characteristic impedance 50J1.
Cable capacitance 126pF. Input voltage max. 500Vp.
Adapter Banana-BNC HZ20
Two 4mm binding posts (19mm between centers) to standard BNC
male plug. Input voltage max. 500Vp.
son Through-Termination HZ22
For terminating systems with 50 Q characteristic impedance.
Modular Probes Maximum load 2W. Max. voltage lOVp^s-
The clear advantage over ordinary probes are field replaceable
parts and the HF-compensation feature on the 10:1 attenuator pro¬
bes. For the first time, probes in this price range allow adjustments
of their FIF-characteristics to match individually the input imped¬
ance of each scope. This is particularly important for scopes with
higher bandwidths (>50MFIz), as otherwise strong overshoot or
rounding may occur, when measuring fast-rising square waves.
An exact FIF-compensation, however, is only possible with square-
wave generators having a risetime <5ns. Most FIAMEG scopes
already feature such a calibration generator. For other oscillo¬
scopes, it is available as accessory item FIZ60-2. At present the
following Modular Probes are available (FIZ36 without HF-com-
pensation);
Type HZ36
selectable
Attenuation Ratio 1:1/10:1
Bandwidth min. (MFIz) 10/100
Risetime (ns) 35/3.5
Inp, Capacitance (pF) 47/18
Inp. Resistance (Mil) 1/10
Inp. Voltage max. (Vp) 600
Cable Length (m) 1.5
Spare Cable for HZ36
Spare Cable for HZ51. HZ54
Sparepart Kit (2 sprung hooks. 2
HZ51 HZ52 HZ53 HZ54
selectable
10:1 10:1 (HF) 100:1 1:1/10:1
150 250 150 10/150
<2
<1.4
<2 35/<2
16 16 6,5 40/18
10
10 100 1/10
600 600 1200 600
1.2 1.5 1,5 1.2
HZ 39
HZ57
tips, 1 ground cable) HZ40
Demodulator Probe HZ55
Special probe for AM-demodulation and wobbulator measure¬
ments. HF-Bandwidth lOOkFIz - 500MFIz (±1dB). AC Input Volt¬
age 250mV - 50Vrms- DC Isolation Voltage 200V DC including
peak AC. Cable length 1.2m.
High Voltage Probe HZ58
For measurement of voltages up to 15kVpp. Input resistance
approx. 500mQ. Recommended load resistance) MQ/10MQ
(switchable). Attenuation ratio 1000:1. Bandwidth 1 MFIz. Cable
length 1.5 m. BNC connector.
Carrying Cases
For HM103 HZ95
For HM 203, HM204, HM205, HM208, HM408, HM604,
HM605 and HM 1005 HZ96
Viewing Hood HZ47
ForHM203, HM204, HM205, HM208, HM408, HM604, HM605
and HM 1005
Scope-Tester HZ 6 O -2
For Checking the Y amplifier, timebase, and compensation of all
probes, the HZ 60-2 is a crystal-controlled, fast rising (typ. 3 ns)
square-wave generator with switchable frequencies of DC, 1-10-
100Hz, 1-IO-IOOkHz, and 1 MHz. Three BNC outputs provide sig¬
nals of 25 mVpp into 50 Q, 0.25 Vpp and 2.5 Vpp (open circuit for 10x and
lOOx probes); accuracy ±1%. Battery-powered.
Component-Tester HZ65
Indispensable for trouble-shooting in electronic circuits. Single
component and in-circuit tests are both possible. The HZ65 oper¬
ates with all scopes, which can be switched to X-Y operation (ext.
horizontal deflection). Non-destructive tests can be carried out on
almost all semiconductors, resistors, capacitors, and coils. Two
sockets provide for quick testing of the 3 junction areas in any small
power transistor. Other components are connected by using 2
banana jacks. Test leads supplied.
Examples of Test Displays:
Short circuit CapacitorSS^F Junction E-C Z-Diode<8V
Printed in West Germany 5/90
zi

Operating Instructions
General Information
Safety
This oscilloscope is easy to operate. The logical arrange¬
ment of the controls allows anyone to become familiar with
the operation of the instrument after a short time, however,
experienced users are also advised to read through these
instructions so that all functions are understood.
Immediately after unpacking, the instrument should be
checked for mechanical damage and loose parts in the in¬
terior. If there is transport damage, the supplier must be in¬
formed immediately. The instrument must then not be put
into operation.
Check that the instrument is set to the correct mains/line
voltage. If not, refer to instructions on page M2.
Use of tilt handle
To view the screen from the best angle, there are three dif¬
ferent positions (C, D, E)forsetting up the instrument. If the
instrument is set down on the floor after being carried, the
handle remains automatically in the upright carrying posi¬
tion (A).
In order to place the instrument onto a horizontal surface,
the handle should be turned to the upper side of the oscillo¬
scope (C). For the D position (10° inclination), the handle
should be turned in the opposite direction out of the carry¬
ing position until it locks in place automatically underneath
the instrument. For the E position (20° inclination), the
handle should be pulled to release it from the D position and
swing backwards until it locks once more.
The handle may also be set to a position for horizontal carry¬
ing by turning it to the upper side to lock in the B position. At
the same time, the instrument must be moved upwards,
because otherwise the handle will jump back.
This instrument has been designed and tested in accor¬
dance with lEC Publication 348, Safety Requirements for
Eiectronic Measuring Apparatus, and has left the factory
in a safe condition. The present instruction manual contains
important information and warnings which have to be fol¬
lowed by the user to ensure safe operation and to retain the
oscilloscope in safe condition. The case, chassis and all
measuring terminals are connected to the protective earth
contact of the appliance inlet. The instrument operates ac¬
cording to Safety C/ass / ( three-conductor power cord with
protective earthing conductor and a plug with earthing con¬
tact). The mains/line plug shall only be inserted in a socket
outlet provided with a protective earth contact. The protec¬
tive action must not be negated by the use of an extension
cord without a protective conductor.
Warningl Any interruption of the protective conductor
inside or outside the instrument or disconnection of the
protective earth terminai is iikely to make the instru¬
ment dangerous. Intentional interruption of the protec¬
tive earth connection is prohibited. The mains/line piug
should be inserted before connections are made to
measuring circuits.
The grounded accessible metal parts (case, sockets, jacks)
and the mains/line supply contacts (line, neutral) of the in¬
strument have been tested against insulation breakdown
with 2000Vr.m.s. (50Hz).
Under certain conditions, 50 Hz or 60 Hz hum voltages can
occur in the measuring circuit due to the interconnection
with other mains/line powered equipment or instruments.
This can be avoided by using an isolation transformer
(Safety Class II). When displaying waveforms where the
"low-level" side of the signal is at a high potential, even
with the use of a protective isolation transformer, it should
be noted that this potential is connected to the oscillo¬
scope's case and other accessible metal parts. High volt¬
ages are dangerous. In this case, special safety precautions
are to be taken, which must be supervised by qualified per¬
sonnel if the voltage is higher than 42 V.
Most cathode-ray tubes develop X-rays. However, the
dose equivalent rate falls far below the maximum per¬
missible value of 36pA/kg (O.SmR/h).
Whenever it is likely that protection has been impaired, the
instrument shall be made inoperative and be secured
against any unintended operation. The protection is likely to
be impaired if, for example, the instrument
- shows visible damage,
- fails to perform the intended measurements,
- has been subjected to prolonged storage under un¬
favourable conditions (e.g. in the open or in moist envi¬
ronments),
- has been subject to severe transport stress (e.g. in poor
packaging).
Subject to change without notice
Ml

Operating conditions
Maintenance
The instrument has been designed for indoor use.
The permissible ambient temperature range during opera¬
tion is -I-10°C... -t-40°C. It may occasionally be subjected to
temperatures between -l-10°Cand -10°C without degrad¬
ing its safety. The permissible ambient temperature range
for storage or transportation is -40°C ... -I-70°C.
The maximum operating altitude is up to 2200 m (non¬
operating 15000 m). The maximum relative humidity is up
to 80%.
If condensed water exists in the instrument it should be
acclimatized before switching on. In some cases (e.g.
extremely cold oscilloscope) two hours should be allowed
before the instrument is put into operation. The instrument
should be kept in a clean and dry room and must not be
operated in explosive, corrosive, dusty, or moist environ¬
ments. The oscilloscope can be operated in any position,
but the convection cooling must not be impaired. The ven¬
tilation holes may not be covered. For continuous opera¬
tion the instrument should be used in the horizontal posi¬
tion, preferably tilted upwards, resting on the tilt handle.
The specifications stating tolerances are only valid if
the instrument has warmed up for 30 minutes at an
ambient temperature between -h15C°and +30C°. Val¬
ues not stating tolerances are typical for an average
instrument.
Guarantee
Each instrument runs through a quality test with 10 hour
burn-in before leaving the production. Practically every early
failure is detected in intermittent operation by this method.
However, it is possible that a component fails only after a
lengthy operating period. Therefore a functional guaran¬
tee of 2 years is given for all units. The condition for this is
that no modifications have been made in the instrument. In
the case of shipments by post, rail or carrier it is recom¬
mended that the original packing is carefully preserved.
Transport damages and damage due to gross negligence
are not covered by the guarantee.
In the case of a complaint, a label should be attached to the
housing of the instrument which describes briefly the faults
observed. If at the same time the name and telephone
number (dialing code and telephone or direct number or
department designation) is stated for possible queries, this
helps towards speeding up the processing of guarantee
claims.
Various important properties of the oscilloscope should be
carefully checked at certain intervals. Only in this way is it
largely certain that all signals are displayed with the accu¬
racy on which the technical data are based. The test
methods described in the test plan of this manual can be
performed without great expenditure on measuring instru¬
ments. However, purchase of the new HAM EG scope test¬
er HZ 60, which despite its low price is highly suitable for
tasks of this type, is very much recommended.
The exterior of the oscilloscope should be cleaned regularly
with a dusting brush. Dirt which is difficult to remove on the
casing and handle, the plastic and aluminium parts, can be
removed with a moistened cloth (99% water -Fl % mild
detergent). Spirit or washing benzine (petroleum ether) can
be used to remove greasy dirt. The screen may be cleaned
with water or washing benzine (but not with spirit (alcohol)
or solvents), it must then be wiped with a dry clean lint-free
cloth. Under no circumstances may the cleaning fluid get
into the instrument. The use of other cleaning agents can
attack the plastic and paint surfaces.
Switching over the mains/line voltage
The instrument is set for 220 V line voltage on delivery. It
can be switched over to other voltages at the fuse holder
combined with the 3-pole appliance inlet at the rear of the
instrument. Firstly the fuse holder printed with the voltage
values is removed using a small screw driver and - if
required - provided with another fuse. Refer to the table
below for the prescribed value of the fuse. Then replace the
fuse holder so that the impressed white triangle points to
the desired voltage. Here pay attention that the cover plate
is also correctly engaged. The use of repaired fuses or short
circuiting the fuse holder is not allowed. Damage arising
because of this is not covered by the guarantee.
220
R \
ir> N>
CM
1- o
0
0
1
oil
V-
y
Fuse type: Size 5 x 20 mm; 250 V~, C;
lEC 127, Sheet III; DIN
sheet 3).
Cutoff: time lag (T).
Line voltage
110V~±10%
125V~±10%
220V~±10%
240V~±10%
41 662 (possibly DIN 41 571
Fuse rating
T0.63 A
T0.63 A
T0.315A
T0.315A
M2 Subject to change without notice

Type of the signal voltage
With the HM 203-7, practically all periodically repeating sig¬
nals with the frequency spectrum below 20 MHz can be
examined. The display of simple electrical processes, such
as sinusoidal RF and LF signals or line frequency hum volt¬
ages is straightforward. When recording square-wave or
pulse-type signal voltages, it must be noted that their har¬
monics must also be transmitted. The repetition frequency
of the signal must therefore be significantly smaller than the
upper limit frequency of the vertical amplifier. Accurate
evaluation of such signals is only possible up to approxi¬
mately 2 MHz repetition frequency.
Displaying composite signals can be difficult, especially if
they contain no repetive higher amplitude content which
can be used for triggering. This is the case with bursts, for
instance. To obtain a well-triggered display in this case, the
assistance of the variable holdoff and/or variable time con¬
trol may be required.
Television video signals are relatively easyto trigger using
the built-in TV-Sync-Separator with correct trigger slope
setting.
For optional operation as a DC or AC voltage amplifier, the
vertical amplifier input is provided with a DC/AC switch.
The DC position should only be used with a series-con¬
nected attenuator probe or at very low frequencies or if the
measurement of the DC voltage content of the signal is
absolutely necessary.
When displaying very low frequency pulses, the flat tops
may be sloping with AC coupling of the vertical amplifier
(AC limit frequency approx. 1.6 Hz for -3dB). In this case,
DC operation is preferred, provided the signal voltage is not
superimposed on a too high DC level. Otherwise a capacitor
of adequate capacitance must be connected to the input of
the vertical amplifier with DC coupling. This capacitor must
have a sufficiently high breakdown voltage rating. DC cou¬
pling is also recommended for the display of logic and pulse
signals, especially if the pulse duty factor changes con¬
stantly. Otherwise the display will move upwards or down¬
wards at each change. Pure direct voltages can only be
measured with DC-coupling.
Amplitude Measurements
In general electrical engineering, alternating voltage data
normally refers to effective values (rms = root-mean-
square value). However, for signal magnitudes and voltage
designations in oscilloscope measurements, the peak-to-
peak voltage (Vpp) value is applied. The latter corresponds to
the real potential difference between the most positive and
most negative points of a signal waveform.
If a sinusoidal waveform, displayed on the oscilloscope
screen, is to be converted into an effective (rms) value, the
resulting peak-to-peak value must be divided by 2xy~2 =
2.83. Conversely, it should be observed that sinusoidal volt¬
ages indicated in (Veff) have 2.83 times the potential dif¬
ference in Vpp. The relationship between the different volt¬
age magnitudes can be seen from the following figure.
Voltage values of a sine curve
V,ms = effective value; Vp = simple peak or crest value:
Vpp = peak-to-peak value: '^mom = momentary value.
The minimum signal voltage which must be applied to the Y
input for a trace of 1 div. height is ImVpp when the Y
MAG.xS pushbutton is depressed, the VOLTS/DIV.
switch is set to BmV/div., and the vernier is set to CAL by
turning the fine adjustment knob of the VOLTS/DIV.
switch clockwise all the way. However, smaller signals than
this may also be displayed. The deflection coefficients on
the input attenuators are indicated in mV/div. or V/div.
(peak-to-peak value).
The magnitude of the applied voltage is ascertained by
multiplying the selected deflection coefficient by the
vertical display height in div.
If an attenuator probe xIOis used, a further multiplica¬
tion by a factor of 10 is required to ascertain the correct
voltage value.
For exact amplitude measurements, the variable con¬
trol on the attenuator switch must be set to its calibra¬
ted detent CAL. When turning the variable control ccw,
the sensitivity will be reduced by a factor of 2.5.
Therefore every intermediate value is possible within
the 1-2-5 sequence.
With direct connection to the vertical input, signals up to
lOOVpp may be displayed (attenuator set to 5V/div., vari¬
able control to left stop).
With the designations
H = display height in div.,
U = signal voltage in Vpp at the vertical input,
D = deflection coefficient in V/div. at attenuator switch,
the required quantity can be calculated from the two given
quantities:
U-DH H.U D = U
Subject to change without notice
M3 203-7

However, these three values are not freely selectable. They
have to be within the following limits (trigger threshold,
accuracy of reading):
H between 0.5 and 8div., if possible 3.2 to 8div.,
U between 1 mVpp and 40Vpp,
D between 1 mV/div. and 5V/div. in 1-2-5 sequence.
Examples:
Set deflection coefficient D = 50mV/div. ^ 0.05 V/div.,
observed display height H = 4.6 div.,
required voltage U = 0.05 -4.6 = 0.23 Vpp.
Input voltage U = 5Vpp,
set deflection coefficient D = 1 V/div.,
required display height H = 5:1 = 5div.
Signal voltage U = 220\/,^,-2-VY = 622 Vpp
(voltage > 40Vpp, with probe x 100: U = 6.22 Vpp),
desired display height H = min. 3.2div., max. 8div.,
max. deflection coefficient D = 6.22:3.2 = 1.94V/div.,
min. deflection coefficient D = 6.22:8 = 0.78V/div.,
adjusted deflection coefficient D = 1 V/div.
If the applied signal is superimposed on a DC (direct
voltage) level the total value (DC + peak value of the
alternating voltage) of the signal across the Y-input
must not exceed ±400V (see figure). This same limit
applies to normal xIO attenuator probes, the attenuation
ratio of which allows signal voltages up to approximately
400Vpp to be evaluated. Voltages of up to approximately
2,400Vpp may be measured by using the HZ53 high voltage
probe which has an attenuation ratio of 100:1. It should be
noted that its ACpeak value is derated at higher frequencies.
If a normal xIO probe is used to measure high voltages
there is the risk that the compensation trimmer bridging the
attenuator series resistor will break down causing damage
to the input of the oscilloscope. However, if for example
only the residual ripple of a high voltage is to be displayed on
the oscilloscope, a normal xIO probe is sufficient. In this
case, an appropriate high voltage capacitor (approx. 22-
68 nF) must be connected in series with the input tip of the
probe.
Voltage
Total value of input voltage
The dotted line shows a voltage alternating at zero volt level. When superim¬
posed a DC level, the addition of the positive peak and the DC voltage results
in the max. voltage (DC -i- ACpeaJ.
It is very important that the oscilloscope input coupling is
set to DC, if an attenuator probe is used for voltages higher
than 400V (see page IVI6: Connection of Test Signal).
With Y-POS. control (input coupling to GD) it is possible to
set a horizontal graticule line as reference line for ground
potential before the measurement. It can lie below or
above the horizontal central line according to whether posi¬
tive and/or negative deviations from the ground poterntial
are to be measured. Certain switchable xIO/xl attenuator
probes also have a built-in ground reference switch posi¬
tion.
Time Measurements
As a rule, most signals to be displayed are periodically
repeating processes, also called periods. The number of
periods per second is the repetition frequency. Depending
on the time base setting of the TIME/DIV. switch, one or
several signal periods or only a part of a period can be dis¬
played. The time coefficients are stated in ms/div. and \>s/
div. on the TIME/DIV.-switch. The scale is accordingly
divided into two fields.
The duration of a signal period or a part of it is deter¬
mined by multipiying the reievant time (horizontal dis¬
tance in div.) by the time coefficient set on the TIME/
DlM.-switch.
The variabie time control (identified with an arrow
knob cap) must be in its caiibrated position CAL. (arrow
pointing horizontally to the right).
With the designations
L = displayed wave length in div. of one period,
T = time In seconds for one period,
F = recurrence frequency in Hz of the signal,
Tc = time coefficient in s/div. on timebase switch and
the relation F = 1 /T, the following equations can be stated;
H
II
1“ t-
II
II
P-lH
F - , 1_
L - .1
T - ^
L’Tc
F-Tc
LF
With depressed X-MAG. x10 pushbutton the Tg value
must be divided by 10.
However, these four values are not freely selectable. They
have to be within the following limits:
L between 0.2 and lOdiv., if possible 4 to lOdiv.,
T between 0.02 [xs and 1 s,
F between 0.5 Hz and 20 MHz,
Tc between 0.2[is/div. and 0.1 s/div. in 1-2-5 sequence
(with X-MAG. xIO in out position), and
Tc between 20ns/div. and 10 ms/div. in 1-2-5 sequence
(with pushed X-MAG. x 10 pushbutton).
M4 203-7
Subject to change without notice

Examples:
Displayed wavelength L = 7div.,
set time coefficient = 0.2 ^is/div.,
required period T = 7 0.2-10”® = 1.4(is
required rec. freq. F = 1 ;(1.4-10”®) = 714 kHz.
Signal period T = 0.5s,
set time coefficient = 0.2s/div.,
required wavelength L = 0.5:0.2 = 2.5div..
Displayed ripple wavelength L = 1 div.,
set time coefficient = 10 ms/div.,
required ripple freq. F = 1 : (1 -lO-IO”®) = 100 Hz.
TV-line frequency F = 15 625 Hz,
set time coefficient Tc = lO^rs/div.,
required wavelength L = 1 :(15 625 -10“®) = 6.4div..
Sine wavelength L = min. 4div., max. 10div.,
Frequency F = 1 kHz,
max. time coefficient T;, = 1: (4-10®) = 0.25 ms/div.,
min. time coefficient Tc = 1 :(10-10®) = 0.1 ms/div.,
set time coefficient = 0.2 ms/div.,
required wavelength L = 1 (10® 0.2 10“®) = 5div.
Displayed wavelength L = O.Sdiv.,
set time coefficient T,, = 0.5pis/div.,
pressedX-MAG. xIO button: = 0.05^is/div.,
required rec. freq. F = 1: (0.8-0.05-10“®) = 25 MHz,
required period T = 1: (25 -10®) = 40 ns.
If the time is relatively short as compared with the complete
signal period, an expanded time scale should always be
applied (X-MAG. xIO button pressed). In this case, the
ascertained time values have to be divided by 10. The time
interval of interest can be shifted to the screen center using
the X-POS. control.
The following figure shows correct positioning of the oscil¬
loscope trace for accurate risetime measurement.
100 %
90%
10 %
0
With a time coefficient of 0.2ns/div. and pushed X-MAG
xIO button the example shown in the above figure results
in a measured total risetime of
t,ot = 1.6div.-0.2ns/div.: 10 = 32ns
When very fast risetimes are being measured, the rise-
times of the oscilloscope amplifier and of the attenuator
probe has to be deducted from the measured time value.
The risetime of the signal can be calculated using the fol¬
lowing formula.
In this ttot is the total measured risetime, tosc is the risetime
of the oscilloscope amplifier (approx. 17,5 ns), and tp the
risetime of the probe (e.g. = 2 ns). If ttot is greater than
100 ns, then t^t can be taken as the risetime of the pulse,
and calculation is unnecessary.
Calculation of the example in the figure above results in a
signal risetime
When investigating pulse or square waveforms, the critical
feature is the risetime of the voltage step. To ensure that
transients, ramp-offs, and bandwidth limits do not unduly
influence the measuring accuracy, the risetime is generally
measured between 70% and 90% of the vertical pulse
height. For peak-to-peak signal amplitude of 6div. height,
which are symmetrically adjusted to the horizontal center
line, the internal graticule of the CRT has two horizontal dot¬
ted lines ±2.4div. from the center line. Adjust the Y
attenuator switch with its variable control together with the
Y-POS. control so that the pulse height is precisely aligned
with these 0 and 100 % lines. The 10 % and 90 % points of
the signal will now coincide with the two lines, which have
a distance of ±2.4div. from the horizontal center line and an
additional subdivision of 0.2 div. The risetime is given by
the product of the horizontai distance in div. between
these two coincidence points and the time coefficient
setting. If magnification is used, this product must be
divided by 10. The /a/Zf/meof a pulsecan also be measured
by using this method.
tr = y 32® - 17.5® - 2® = 26.27 ns
The measurement of the rise or fall time is not limited to the
trace dimensions shown in the above diagram. It is only par¬
ticularly simple in this way. In principle it is possible to
measure in any display position and at any signal amplitude.
It is only important that the full height of the signal edge of
interest is visible in its full length at not too great steepness
and that the horizontal distance at 10% and 90% of the
amplitude is measured. If the edge shows rounding or over¬
shooting, the 100% should not be related to the peak val¬
ues but to the mean pulse heights. Breaks or peaks
(glitches) next to the edge are also not taken into account.
With very severe transient distortions, the rise and fall time
measurement has little sense. For amplifiers with approxi¬
mately constant group delay (therefore good pulse trans¬
mission performance) the following numerical relationship
between rise time tr {in ns) and bandwidth B (in MHz)
applies;
tr = 3|0
B tr
Subject to change without notice M5 203-7

Connection of Test Signal
Caution: When connecting unknown signals to the oscillo¬
scope input, always use automatic triggering and set the
DC-AC input coupling switch to AC. The attenuator switch
should initially be set to 5 V/div..
Sometimes the trace will disappear after an input signal has
been applied. The attenuator switch must then be turned
back to the left, until the vertical signal height is only 3-8div.
With a signal amplitude greater than lOOVpp, an attenuator
probe must be inserted before the oscilloscope's vertical
input. If, after applying the signal, the trace is nearly
blanked, the period of the signal is probably substantially
longer than the set value on the TIME/DIV. switch. It
should be turned to the left to an adequately larger time
coefficient.
The signal to be displayed can be connected directly to the
Y-input of the oscilloscope with a shielded test cable such
as HZ 32 and HZ 34 or attenuated through a xIO or xlOO
attenuator probe. The use of test cables with high imped¬
ance circuits is only recommended for relatively low fre¬
quencies (up to approx. 50 kHz). For higher frequencies, the
signal source must be of low impedance, i.e. matched to
the characteristic resistance of the cable (as a rule 50 Ohm).
Especially when transmitting square and pulse signals, a
resistor equal to the characteristic impedance of the cable
must also be connected across the cable directly at the Y-
input of the oscilloscope. When using a 50 Ohm cable such
as the HZ 34, a 50 Ohm through termination type HZ22 is
available from HAMEG. When transmitting square signals
with short rise times, transient phenomena on the edges
and top of the signal may become visible if the correct ter¬
mination is not used. A terminating resistance is some¬
times recommended with sine signals as well. Certain
amplifiers, generators or their attenuators maintain the
nominal output voltage independent of frequency only if
their connection cable is terminated with the prescribed
resistance. Here it must be noted that the terminating resis¬
tor HZ 22 will only dissipate a maximum of 2 Watts. This
power is reached with 10 V^ms or - at 28.3 Vpp with sine sig¬
nal.
If a x10 or x100 attenuator probe is used, no termination is
necessary. In this case, the connecting cable is matched
directly to the high impedance input of the oscilloscope.
When using attenuators probes, even high internal imped¬
ance sources are only slightly loaded (approx. 10 MQ II 16
pF or 100 MQ II 7 pF with HZ 53). Therefore, if the voltage
loss due to the attenuation of the probe can be compen¬
sated by a higher amplitude setting, the probe should
always be used. The series impedance of the probe pro¬
vides a certain amount of protection for the input of the ver¬
tical amplifier. Because of their separate manufacture, all
attenuator probes are only partially compensated, therefore
accurate compensation must be performed on the oscillo¬
scope (see "Probe compensation" page M7).
Standard attenuator probes on the oscilloscope normally
reduce its bandwidth and increase the rise time. In all cases
where the oscilloscope band width must be fully utilized
(e.g. for pulses with steep edges) we strongly advise using
the modular probes HZ 51 (x10) HZ52{x^ 0 HF) and HZ54
(x1 and xIO, see oscilloscope accessories, page Z1). This
can save the purchase of an oscilloscope with larger
bandwidth and has the advantage that defective compo¬
nents can be ordered from HAMEG and replaced by one¬
self. The probes mentioned havea HF-calibration in addition
to low frequency calibration adjustment. Thus a group delay
correction to the upper limit frequency of the oscilloscope is
possible with the aid of an 1 MHz calibrator, e.g. HZ60. In
fact the bandwidth and rise time of the oscilloscope are not
noticably changed with these probe types and the wave¬
form reproduction fidelity can even be improved because
the probe can be matched to the oscilloscope's individual
pulse response.
If a xIO orxIOO attenuator probe is used, DC input cou¬
pling must always be used at voltages above 400 V.
With AC coupling of low frequency signals, the attenuation
is no longer independent of frequency, pulses can show
pulse tilts. Direct voltages are suppressed but load the oscil¬
loscope input coupling capacitor concerned. Its voltage rat¬
ing is max. 400 V (DC -F peak AC). DC input coupling is
therefore of quite special importance with a xlOO attenua¬
tion probe which usually has a voltage rating of max. 1 200
V (DC + peak AC). A capacitor of corresponding capaci¬
tance and voltage rating may be connected in series with
the attenuator probe input for blocking DC voltage (e.g. for
hum voltage measurement).
With all attenuator probes, the maximum AC input volt¬
age must be derated with frequency usually above 20 kHz.
Therefore the derating curve of the attenuator probe type
concerned must be taken into account.
The selection of the ground point on the test object is impor¬
tant when displaying small signal voltages. It should always
be as close as possible to the measuring point. If this is not
done, serious signal distortion may result from spurious cur¬
rents through the ground leads or chassis parts. The ground
leads on attenuator probes are also particularly critical. They
should be as short and thick as possible. When the
attenuator probe is connected to a BNC-socket, a BNC-
adapter, which is often supplied as probe accessory, should
be used. In this way ground and matching problems are
eliminated.
Hum or interference appearing in the measuring circuit
(especially when a small deflection coefficient is used) is
possibly caused by multiple grounding because equalizing
M6 203-7
Subject to change without notice