Hameg HM 407A Manual

15Subject to change without noticeAttention!In XY mode the 0 Volt reference symbol is automaticallyswitched off.STORAGE MODE ONLYThe Y-POS. II knob can be used for shifting the positionof a signal stored with HOLD. Additional informationrelating to this operation are described under HOLD (7).(15) NM - AT - - Pushbutton with a double function andassociated NM-LED.The following description assumes that Yt (time base)mode has been chosen.NM - AT selectionPress and hold the pushbutton to switch over fromautomatic (peak value) to normal triggering (NM-LEDabove the pushbutton lit) and vice versa. If the LED isdark, automatic (peak value) triggering is selected.Whether the peak value detection in automatic triggermode is automatically activated or not, depends on thetrigger coupling setting (TRIG.MODE (26)). The way thetrigger point symbol in the readout responds on differentLEVEL control knob settings indicates the situation:1.If the trigger symbol can not be shifted in the verticaldirection when a signal is not applied or the signal heightis not sufficient, the peak value detection is active.2.Under the condition that the trigger point symbol cannotbe shifted in such a way that it leaves the signal displayon the screen, the peak value detection is active.3.The peak value detection is switched off if the triggerpoint can be set outside the maximum peak values ofthe signal, thus causing an untriggered signal display.Slope selectionBriefly pressing this pushbutton selects which slope ofthe signal is used for triggering the time base generator.Each time this pushbutton is briefly pressed, the slopedirection switches from falling edge to rising edge andvice versa. The current setting is displayed in the readoutby a slope symbol.ANALOG MODE ONLYThe last setting in undelayed time base mode is storedand still active if triggered DELAY (DTR) time base modeis selected. This allows for a different slope setting for thetriggered DELAY (DTR) time base mode.(16) TR - Trigger indicator LED.The TR LED is lit in Yt (time base) mode if the triggeringconditions are met. Whether the LED flashes or is litconstantly depends on the frequency of the trigger signal.(17) LEVEL - Control knob.Turning the LEVEL knob causes a different trigger pointsetting (voltage). The trigger unit starts the time basewhen the edge of a trigger signal crosses the triggerpoint. In most Yt modes the trigger point is displayed inthe readout by the symbol on the left vertical graticuleline. If the trigger point symbol would overwrite otherreadout information or would be invisible when being setabove or below the screen, the symbol changes and anarrow indicates in which vertical direction the triggerpoint has left the screen.The trigger point symbol is automatically switched off inthose modes where there is no direct relation betweenthe trigger signal and the displayed signal.ANALOG MODE ONLYThe last setting in undelayed time base mode is storedand still active if triggered DELAY (DTR) time base modeis selected. This allows for a different level setting for thetriggered DELAY (DTR) time base mode.STORAGE MODE ONLYIn storage mode the trigger point symbol also indicatesthe post or pre-trigger condition by a horizontal positionshift.Please note PTR (8).(18) X-POS. - Control knob.This control knob enables an X position shift of thesignal(s) in Yt (time base) and analog XY mode. Incombination with X magnification x10 (Yt mode) thisfunction makes it possible to shift any part of the signalon the screen.STORAGE MODE ONLYIn XY mode the X-POS. knob is inoperative. The Y-POS.I (13) must be used for X-position shift.(19) X-MAG. x10 - Pushbutton and LED.Each time this pushbutton is pressed the x10 LED locatedabove is switched on or off. If the x10 LED is lit, the signaldisplay in all Yt (time base) modes is expanded 10 fold andconsequently only a tenth part of the signal curve isvisible. The interesting part of the signal can be madevisible with aid of the X-POS. (18) control. As the Xexpansion results in a higher time base speed (lower timedeflection coefficient), all time and frequency relevantinformation in the readout is switched over.This pushbutton is not operative in XY mode.ANALOG MODE ONLYThe expansion is 5 fold if the time base is set to 50ns/div.Consequently the lowest time deflection coefficient is10ns/div.(20) VOLTS/DIV. - Control knob and associated LED.This control knob for channel I has a double function. Thefollowing description relates to the input attenuatorfunction (VAR-LED dark).This control knob is operative in those modes wherechannel I is active (CH I, DUAL, ADD and XY) and theinput coupling is not set to ground (GD (33)).Controls and readout