Operating Instructions

General Information

Safety

This oscilloscope is easy to operate. The logical arrangement 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 interior. If there is transport damage, the supplier must be informed 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 different positions (C, D, E) for setting up the instrument. If the instrument is set down on the floor after being carried, the handle remains automatically in the upright carrying position (A).

In order to place the instrument onto a horizontal surface, the handle should be turned to the upper side of the oscilloscope (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 carrying 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 accordance with IEC Publication 348, Safety Requirements for

Electronic Measuring Apparatus, and has left the factory in a safe condition. The present instruction manual contains important information and warnings which have to be followed 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 according to Safety C/ass I (three-conductor power cord with protective earthing conductor and a plug with earthing contact). The mains/line plug shall only be inserted in a socket outlet provided with a protective earth contact. The protective action must not be negated by the use of an extension cord without a protective conductor.

Warning! Any interruption of the protective conductor inside or outside the instrument or disconnection of the protective earth terminal is likely to make the instrument dangerous. Intentional interruption of the protective earth connection is prohibited. The mains/line plug 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 instrument have been tested against insulation breakdown with 2000 Vr.m.s. (50Hz).

Under certain conditions, 50 Hz or 60Hz 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) between the mains/line outlet and the power plug of the instrument. 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 oscilloscope's case and other accessible metal parts. High voltages are dangerous. In this case, special safety precautions are to be taken, which must be supervised by qualified personnel if the voltage is higher than 42V.

Most cathode-ray tubes develop X-rays. However, the dose equivalent rate falls far below the maximum permissible value of 36pA/kg (0.5mR/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 Ii kely to be impaired if, for example, the instrument shows visible damage, fails to perform the intended measurements, has been subjected to prolonged storage under unfavourable conditions (e.g. in the open or in moist environments), has been subject to severe transport stress (e.g. in poor packaging).

Operating conditions

Maintenance

The instrument has been designed for indoor use. The permissible ambient temperature range during operation is + 15°C ... +30°C. It may occasionally be subjected to temperatures between + 10°C and — 10°C without degrading its safety. The permissible ambient temperature range for storage or transportation is -40°C .+70°C.

The maximum operating altitude is up to 2200m (non-operating 15000m). The maximum relative humidity is up to 80%.

If condensed water exists in the instrument it should be 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 environments 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 the horizontal position, 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 +15C° and +30C°. Values not stating tolerances are typical for an average instrument.

Warranty

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 guarantee 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 recommended 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 accuracy 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 instruments. However, purchase of the new HAM EG scope tester 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 +1 % 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 220V (240V U.K.) 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.

IEC 127, Sheet III; DIN 41 662 (possibly DIN 41 571

Line voltage Fuse rating

Type of Signal

All types of signals with a frequency spectrum below 60 MHz can be displayed on the HM 604. The display of simple electrical processes such as sinusoidal RF and AF signals or ripple poses no problems. However, when square or pulse-shaped signals are displayed it must be remembered that their harmonic content must also be transmitted. In this case, the bandwidth of the vertical amplifier must be considerably higher than the repetition frequency of the signal. In view of this, accurate evaluation of such signals with the HM 604 is only possible up to a maximum repetition rate of6MHz. Operating problems can sometimes occur when composite signals are to be displayed, especially if they do not contain any suitable level components and repetition frequency which can be used for triggering. This occurs, for example, with burst signals. To obtain a stably triggered display in these cases, it may be necessary to use Normal Triggering, HOLD OFF time control, and/or TIME/DIV. variable control.

Video signals are easily triggerable by the aid of the active TV sync separator (TV SEP. switch).

For optional operation as a DC or AC voltage amplifier, each channel is provided with a DC-AC coupling switch. The DC position should only be used with an attenuator probe or at very low frequencies or if the determination of DC voltage content of the signal is absolutely necessary.

However, when investigating very low-frequency pulses, misleading ramp-offs may occur with AC coupling. In this case, DC operation is to be preferred if the signal voltage is not superimposed on a too high DC voltage level. Otherwise, a capacitor of adequate capacitance must be connected before the input of the vertical amplifier (switched to DC coupling). It should be remembered that this capacitor must have a sufficiently high breakdown voltage. DC operation is also recommended for the display of logic and pulse signals, particularly if their pulse duty factor changes permanently during operation. Otherwise, the display will move up and down with any change. DC voltages can only be measured in the DC position.

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-peakvoltage (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 Ixfl. = 2.83. Conversely, it should be observed that sinusoidal voltages indicated in Vrms(Veff) have 2.83 times the potential difference in V,,. 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.

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 required at the vertical amplifier input for a display of 1 cm is approximately 1mVpp. This is achieved with the attenuator control set at 5mV/cm, its variable control in the fully clockwise position and pulled out. However, smaller signals than this may also be displayed. The deflection coefficients on the input attenuators are indicated in mV/cm or V/cm (peak-to-peak value).

The magnitude of the applied voltage is ascertained by multiplying the selected deflection coefficient by the vertical display height in cm.

If an attenuator probe x 70 is used, a further multiplication by a factor of 70 is required to ascertain the correct voltage value.

For exact amplitude measurements the variable control on the attenuator switch must be set to its calibrated detent CAL. When turning the variable control ccw the sensitivity will be decreased by a factor of 2.5. Therefore every intermediate value is possible within the 7-2-5 sequence.

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

When pulling the variable control knob (MAG x5), the sensitivity is increased by a factor of 5. Hence follows a min. deflection coefficient of 1 mV/cm (reduced bandwidth).

With the designations H = display height in cm, U = signal voltage in Vpp at the vertical input, D = deflection coefficient in V/cm at attenuator switch, the required quantity 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 8cm, if possible 3.2 to 8cm, U between 1 mVpp and 160Vpp, D between 5mV/cm and 20V/cm in I-2-5 sequence. D between 1 mV/cm and 4V/cm in 1-2-5 sequence (with pulled MAG x5 knob).

Examples:

Set deflection coefficient D = 50 mV/cm ^ 0.05 V/cm, observed display height H = 4.6 cm, required voltage U = 0.05-4.6 = 0.23 V„.

Input voltage U = 5Vpp, set deflection coefficient D = 1 V/cm, required display height H = 5: 1 = 5cm

Signal voltage U = 220Vrms-2-l/T = 622 Vpp (voltage >160Vpp, with probe X 10 : U = 62.2 Vpp), desired display height H = min. 3.2cm, max. 8cm, max. deflection coefficient D = 62.2 : 3.2 = 19.4'V/cm, min. deflection coefficient D = 62.2 :8 = 7.8V/cm, adjusted deflection coefficient D = 10V/cm

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 ±400 V(see figure). This same limit applies to normal x 10 attenuator probes, the attenuation ratio of which allows signal voltages up to approximately 1 ,000Vpp 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 x 10 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 x 10 probe is sufficient. In this case, an appropriate high voltage capacitor (approx. 22-68nF) must be connected in series with the input tip of the probe.

Voltage

The dotted line shows a voltage alternating at zero volt level. When superimposed a DC level, the addition of the positive peak and the DC voltage results in the max. voltage (DC + AC,,,,).

The dotted line shows a voltage alternating at zero volt level. When superimposed a DC level, the addition of the positive peak and the DC voltage results in the max. voltage (DC + AC,,,,).

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 M6: Connection of Test Signal).

Time Measurements

As a rule, all signals to be displayed are periodically repeating processes and can also be designated as periods. The number of periods per second is the recurrence frequency or repetition rate. One or more signal periods or even part of a period may be shown as a function of the adjustment of the TIME/DIV. switch. The time coefficients on the TIME/ DIV. switch are indicated in s/cm, ms/cm, and |is/cm. Accordingly, the dial is subdivided into three sectors. The duration of a signal period or a portion of the waveform is ascertained by multiplying the relevant time (horizontal distance in cm) by the time coefficient selected on the TIME/DIV. switch. The time variable control (small knob on the TIME/DIV. switch) must be in its calibrated detent CAL. for accurate measurement (arrow horizontal and pointing to the right). With the designations

L = displayed wave length in cm of one period, T = time in seconds for one period, F = recurrence frequency in Hz of the signal, Tc = time coefficient in s/cm on timebase switch and the relation F = 1/T, the following equations can be stated :

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