User manual

33
Analysis
pected which will point to the defective component. Rather
exact results may be achieved if the measurements are
compared to those of intact components. This is especially
true for semiconductors. The polarity of diodes or transis-
torscanthusbeidentiediftheletteringormarkingismis-
sing. Please note that with semiconductors changing the
polarity will cause the display to rotate 180 degrees around
the screen center. More important in practice is the quick
determination of plain shorts and opens which are the most
common causes of requiring service.
9.5.1 In-circuit tests
They are possible in many cases but deliver rarely clear
results. By paralleling of real or complex impedances – es-
pecially if those are fairly low impedance at 50 Hz/200 Hz
– there will be mostly great differences compared to
individual components. If circuits of the same type have to
be tested often (service), comparisons with intact circuits
may help again. This is also quickly done because the intact
circuit has not to be functional, also it should not be ener-
gized. Just probe the various test points with the cables of
the component tester of the unit under test and the intact
unit and compare the screen displays. Sometimes the unit
under test may already contain an intact portion of the
same type, this ist e.g. the case with stereo circuits, push-
pull circuits or symmetrical bridge circuits. In cases of doubt
one side of the dubious component can be unsoldered.
9.6 Digital Voltmeter
The digital voltmeter completely captures input data with
the selected vertical sensitivity and the basic accuracy of
the ADC. The digital voltmeter is independent from the
capture settings and the post processing of the trans-
former values. Determine the values by means of the
measurementintervaltoensurethedenedfrequency
range of 20 Hz to 100 kHz. All measurements are perfor-
med by means of this measurement interval which ensu-
res that the DC portion can also be reliably captured for
low-frequency signals.
The analysis function DIG. VOLTMETER can be activated
by using the UTIL menu in the VERTICAL control panel.
The digital voltmeter includes a 3-digit voltage display as
Fig. 9.6: Digital Voltmeter.
7-segment display with the use of the analog channels. Four
freelycongurablemeasuringdisplaysarepossiblewhere
two measurement value displays for channel 1 (CH1) and
two measurement value displays for channel 2 (CH2) are
available. For each channel, the measurement displays are
divided into in a primary measurement location (soft menu
key Channel 1 / Channel 2) and a secondary measurement
location (soft menu key SECONDARY). The primary measure-
ment display will be shown in a large font, and the secondary
measurement display in a small font. All measurement dis-
playscanbeconguredseparately.
The following primary and secondary measurement displays
are available:
❙ OFF: Measurement display deactivated
❙ DC: Mean
❙ DC RMS: RMS
❙ AC RMS: Standard Deviation
❙ CREST FACTOR: Crest factor (|X|max/XRMS)
❙ PEAK PEAK: Maximum-Minimum
❙ PEAK +: Maximum
❙ PEAK -: Minimum
Use the soft menu key POSITION to change the display
position of the digital voltmeter on the screen. When the
XY mode is activated, the display position of the digital volt-
meterispredenedandcannotbemodied.Usethesoft
menu key VOLTMETER OFF to deactivate the digital voltme-
ter function and to close the menu.