Hameg HM 407A Manual

7Subject to change without noticeSignal voltage U = 230Vrmsx2√2 = 651Vpp(voltage > 160Vpp, with probe 10:1: U = 65.1Vpp),desired display height H = min. 3.2div, max. 8div,max. deflection coefficient D = 65.1:3.2 = 20.3V/div,min. deflection coefficient D = 65.1:8 = 8.1V/div,adjusted deflection coefficient D = 10V/div.The previous examples are related to the CRT graticule reading.The results can also be determined with the aid of the DVcursor measurement (please note “controls and readout”).The input voltage must not exceed 400V, independent fromthe polarity.If an AC voltage which is superimposed on a DC voltage isapplied, the maximum peak value of both voltages must notexceed + or - 400V. So for AC voltages with a mean value ofzero volt the maximum peak to peak value is 800Vpp.If attenuator probes with higher limits are used, the probeslimits are valid only if the oscilloscope is set to DC inputcoupling.If DC voltages are applied under AC input coupling conditionsthe oscilloscope maximum input voltage value remains 400V.The attenuator consists of a resistor in the probe and the 1MΩinput resistor of the oscilloscope, which are disabled by the ACinput coupling capacity when AC coupling is selected. This alsoapplies to DC voltages with superimposed AC voltages. It alsomust be noted that due to the capacitive resistance of the ACinput coupling capacitor, the attenuation ratio depends on thesignal frequency. For sinewave signals with frequencies higherthan 40Hz this influence is negligible.With the above listed exceptions HAMEG 10:1 probes can beused for DC measurements up to 600V or AC voltages (witha mean value of zero volt) of 1200Vpp. The 100:1 probe HZ53allows for 1200V DC or 2400Vpp for AC.It should be noted that its AC peak value is derated at higherfrequencies. If a normal x10 probe is used to measure highvoltages there is the risk that the compensation trimmerbridging the attenuator series resistor will break down causingdamage to the input of the oscilloscope. However, if forexample only the residual ripple of a high voltage is to bedisplayed on the oscilloscope, a normal x10 probe is sufficient.In this case, an appropriate high voltage capacitor (approx. 22-68nF) must be connected in series with the input tip of theprobe.With Y-POS. control (input coupling to GD) it is possible to usea horizontal graticule line as reference line for ground potentialbefore the measurement. It can lie below or above the horizon-tal central line according to whether positive and/or negativedeviations from the ground potential are to be measured.Total value of input voltageThe dotted line shows a voltage alternating at zero volt level.If superimposed on a DC voltage, the addition of the positivepeak and the DC voltage results in the max. voltage (DC +ACpeak).Time MeasurementsAs a rule, most signals to be displayed are periodically repeatingprocesses, also called periods. The number of periods persecond is the repetition frequency. Depending on the timebase setting (TIME/DIV.-knob) indicated by the readout, one orseveral signal periods or only a part of a period can bedisplayed. The time coefficients are stated in ms/div, μs/div orns/div. The following examples are related to the CRT graticulereading. The results can also be determined with the aid of the∆T and 1/∆T cursor measurement (please note “ controls andreadout”).The duration of a signal period or a part of it is determined bymultiplying the relevant time (horizontal distance in div) by the(calibrated) time coefficient displayed in the readout.Uncalibrated, the time base speed can be reduced until amaximum factor of 2.5 is reached. Therefore any intermediatevalue is possible within the 1-2-5 sequence.With the designationsL = 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 ms, μs or ns/div and the relationF = 1/T, the following equations can be stated:However, these four values are not freely selectable. Theyhave to be within the following limits:L between 0.2 and 10div, if possible 4 to 10div,T between 10ns and 5s,F between 0.5Hz and 100MHz,Tc between 100ns/div and 500ms/div in 1-2-5 sequence(with X-MAG. (x10) inactive), andTc between 10ns/div and 50ms/div in 1-2-5 sequence(with X-MAG. (x10) active).Examples:Displayed wavelength L = 7div,set time coefficient Tc = 100ns/div,required period T = 7x100x10 -9 = 0.7μsrequired rec. freq. F = 1:(0.7x10 -6) = 1.428MHz.Signal period T = 1s,set time coefficient Tc = 0.2s/div,required wavelength L = 1:0.2 = 5div.Displayed ripple wavelength L = 1div,set time coefficient Tc = 10ms/div,required ripple freq. F = 1:(1x10x10 -3) = 100Hz.TV-line frequency F = 15625Hz,set time coefficient Tc = 10μs/div,required wavelength L = 1:(15 625x10 -5 ) = 6.4div.Sine wavelength L = min. 4div, max. 10div,Frequency F = 1kHz,max. time coefficient Tc = 1:(4x10 3 ) = 0.25ms/div,min. time coefficient Tc = 1:(10x10 3) = 0.1ms/div,set time coefficient Tc = 0.2ms/div,required wavelength L = 1:(10 3 x0.2x10 -3) = 5div.Type of signal voltage