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Subject to change without notice

8

Type of signal voltage

Type of signal voltage

The oscilloscope

 HM404

-2

 

allows examination of DC voltages

and most repetitive signals in the frequency range up to at
least 40MHz (-3dB).

The vertical amplifiers have been designed for minimum
overshoot and therefore permit a true signal display.

The display of sinusoidal signals within the bandwidth limits
causes no problems, but an increasing error in measurement
due to gain reduction must be taken into account when
measuring high frequency signals. This error becomes
noticeable at approx. 14MHz. At approx. 18MHz the reduction
is approx. 10% and the real voltage value is 11% higher. The
gain reduction error can not be defined exactly as the -3dB
bandwidth of the amplifiers differ between 40MHz and
42MHz. For sinewave signals the -6dB limit is approx. 50MHz.

When examining square or pulse type waveforms, attention
must be paid to the harmonic content of such signals. The
repetition frequency (fundamental frequency) of the signal
must therefore be significantly smaller than the upper limit
frequency of the vertical amplifier.

Displaying composite signals can be difficult, especially if they
contain no repetitive 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 function or the delayed time base may
be required. Television video signals are relatively easy to
trigger using the built-in TV-Sync-Separator (TV).

For optional operation as a DC or AC voltage amplifier, each
vertical amplifier input is provided with a DC/AC switch. DC
coupling should only be used with a series-connected 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 coupling is also
recommended for the display of logic and pulse signals,
especially if the pulse duty factor changes constantly. Otherwise
the display will move upwards or downwards at each change.
Pure direct voltages can only be measured with DC-coupling.

The input coupling is selectable by the AC/DC pushbutton.
The actual setting is displayed in the readout with the

 ” = ”

symbol for DC- and the

 ”

 ~ 

” 

symbol for AC 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 2x

2 = 2.83. Conversely,

it should be observed that sinusoidal voltages indicated in
Vrms (Veff) have 2.83 times the potential difference in Vpp.
The relationship between the different voltage magnitudes
can be seen from the following figure.

Voltage values of a sine curve

Vrms = effective value; Vp = simple peak or crest value;

Vpp = peak-to-peak value; Vmom = momentary value.

The minimum signal voltage which must be applied to the Y
input for a trace of 1div height is 1mVpp (± 5%) when this
deflection coefficient is displayed on the screen (readout) and
the vernier is switched off (VAR-LED dark). However, smaller
signals than this may also be displayed. The deflection
coefficients 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 x10 is used, a
further multiplication by a factor of 10 is required to ascertain
the correct voltage value.

For exact amplitude measurements, the variable control
(

VAR

) must be set to its calibrated detent

 CAL 

position.

With the variable control activated the deflection sensitivity
can be reduced up to a ratio of 2.5 to 1 (

please note ”controls

and readout”

). Therefore any intermediate value is possible

within the 1-2-5 sequence of the attenuator(s).

With direct connection to the vertical input, signals up
to 400Vpp may be displayed (attenuator set to 20V/
div, variable control to 2.5:1).

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 value can be calculated from the two given
quantities:

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 0.5mVpp and 160Vpp,
D between 1mV/div and 20V/div in 1-2-5 sequence.

Examples:

Set deflection coefficient D = 50mV/div   0.05V/div,

Содержание HM404-2.02

Страница 1: ...Instruments HANDBUCH MANUAL MANUEL Oscilloscope HM404 2 02 ENGLISH...

Страница 2: ...MANUAL HANDBUCH MANUEL...

Страница 3: ...fference measurement in DUAL mode Yt 23 Phase difference measurement in DUAL mode 23 Measurement of an amplitude modulation 23 Triggering and time base 24 Automatic Peak value Triggering 24 Normal Tri...

Страница 4: ...ia the device under test mains line supply test leads control cables and or radiation The device under test as well as the oscilloscope may be effected by such fields Although the interior of the osci...

Страница 5: ...0cm internal graticule Acceleration voltage approx 2000V Trace rotation adjustable on front panel Z Input Intens modulation max 5V TTL Calibrator 0 2V 1 1kHz 1MHz tr 4ns Line voltage 100 240V AC 10 50...

Страница 6: ...The instrument has been designed for indoor use The permissible ambient temperature range during operation is 10 C 50 F 40 C 104 F It may occasionally be subjected to temperatures between 10 C 50 F an...

Страница 7: ...nts The oscilloscope can be operated in any position but the convection cooling must not be impaired The ventilation holes may not be covered For continuous operation the instrument should be used in...

Страница 8: ...upling The input coupling is selectable by the AC DC pushbutton The actual setting is displayed in the readout with the symbol for DC and the symbol for AC coupling Amplitude Measurements In general e...

Страница 9: ...example only the residual ripple of a high voltage is to be displayed on the oscilloscope a normal x10 probe is sufficient In this case an appropriate high voltage capacitor approx 22 68nF must be co...

Страница 10: ...lse and calculation is unnecessary Calculation of the example in the figure above results in a signal risetime tr 162 8 752 22 13 25ns The measurement of the rise or fall time is not limited to the tr...

Страница 11: ...intain 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 resistor HZ22 will onl...

Страница 12: ...ive If the instrument is set to XY mode this control knob is inactive and the X POS knob must be used for a horizontal position shift DC voltage measurement If no signal is applied at the INPUT CHI 26...

Страница 13: ...trigger mode is automatically activated or not depends on the trigger coupling setting TRIG MODE The way the trigger point symbol in the readout responds on different LEVEL control knob settings indic...

Страница 14: ...control knob function between attenuator and vernier variable The current setting is displayed by the VAR LED located above the knob After switching the VAR LED 15 on the deflection coefficient is st...

Страница 15: ...the readout instead of CHP In alternate trigger mode the trigger point symbol is switched off Alternate triggering is not available or automatically switched off under the following conditions ADD add...

Страница 16: ...switch when the VAR LED above it is not lit Then the time deflection coefficient can be set in a 1 2 5 sequence and the time base is calibrated Rotating anticlockwise increases the deflection coeffic...

Страница 17: ...ains calibrated until the vernier knob is operated The readout now indicates T instead of T Rotating further anticlockwise increases the time deflection coefficient uncalibrated until the maximum is r...

Страница 18: ...afety earth contact of the line mains plug The input impedance is approx 1M II 20pF TRIG EXT This BNC socket is the external trigger signal input if external triggering is selected Briefly pressing th...

Страница 19: ...upted dotted line indicates the inactive cursor V t Pressing and holding this pushbutton changes from voltage to time or frequency measurement and vice versa In XY mode the instrument is automatically...

Страница 20: ...s MISCELLANEOUS and FACTORY 1 2 1 MISCELLANEOUS contains 1 2 1 1 CONTROL BEEP ON OFF In OFF condition the acoustic signals actuated by the control limits are switched off Note The default setting is O...

Страница 21: ...xtremely short ground connections which are essential for an undistorted waveform reproduction of non sinusoidal high frequency signals Adjustment at 1kHz The C trimmer adjustment low frequency compen...

Страница 22: ...deflects the beam in vertical direction while the time base causes an X deflection from left to right at the same time Thereafter the beam becomes blanked and fly back occurs The following Yt operati...

Страница 23: ...ng or lagging phase angle In alternate triggering condition phase difference measurement is not possible For greatest accuracy adjust the time base for slightly over one period and approximately the s...

Страница 24: ...l triggering Automatic Peak Value Triggering Instrument specific information can be drawn from the items NM AT 10 and LEVEL 12 in the section Controls and Readout This trigger mode is automatically se...

Страница 25: ...f the trigger signal and the lowest frequency range DC In this coupling mode the trigger signal is coupled galvanically to the trigger unit if normal triggering NM is present Therefore there is no low...

Страница 26: ...connected to a BNC connector for scope input via a shielded cable Between cable and BNC center conductor a resistor of at least 100 should be series connected RF decoupling Often it is advisable to sh...

Страница 27: ...se the holdoff control should be reset into its calibration detent fully ccw otherwise the brightness of the display is reduced drastically The function is shown in the following figures Fig 1 shows a...

Страница 28: ...search operation Photo 3 MODE DEL DELAY TIME DIV 5ms div Trigger coupling TV F Trigger slope falling Delay time 20ms Reducing the time coefficient increasing the time base speed now expands the signa...

Страница 29: ...to the lower half of the CRT The 1mV div and 2mV div deflection coefficient will not be selected by AUTO SET as the bandwidth is reduced on these settings Attention If a signal is applied with a pulse...

Страница 30: ...or under test With high values of resistance the slope will tend towards the horizontal axis and with low values the slope will move towards the vertical axis Values of resistance from 20 to 4 7k can...

Страница 31: ...luding probes between oscilloscope and circuit under test Otherwise both COMPONENT TESTER leads are not isolated against the circuit under test In circuit tests are possible in many cases However they...

Страница 32: ...cable length must be less then 3 meters and must contain 9 screened lines connected 1 1 The oscilloscope RS232 connection 9 pole D SUB female is determined as follows Pin 2 Tx data data from oscillos...

Страница 33: ...33 Subject to change without notice Front Panel HM404 2...

Страница 34: ...Subject to change without notice 34...

Страница 35: ...MANUAL HANDBUCH MANUEL...

Страница 36: ...uk Spain HAMEG S L Villarroel 172 174 08036 BARCELONA Tel f 93 4301597 Telefax 93 321220 E mail email hameg es France HAMEG S a r l 5 9 av de la R publique 94800 VILLEJUIF T l 1 4677 8151 Telefax 1 4...

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