Hameg HM 2005 Manual Download Page 17

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Subject to change without notice

20ms/div up to 20ns/div (without X-MAG. x10) but the
availability depends on the A time base setting. The internal
control of the oscilloscope prevents the B time deflection
coefficient from becoming higher than the A deflection
coefficient, as such an operation condition would make no
sense.

If the A time base setting is 200µs/div the B time base range
from 20ms/div up to 500µs/div is not available and the
maximum time deflection coefficient for B would be 200µs/
div. In the last named condition the change of the A time
base from 200µs/div to 100µs/div switches the B time base
also to 100µs/div. However the B time base setting remains
unchanged if the A time base is set to 500µs/div.

As already mentioned under

DUAL (19)

the channel switching

depends on the time deflection coefficient setting. In the
time base ranges from 500ms/div to 500µs/div chopped
(CHP) channel switching is automatically selected, through
which the switching occurs constantly during the time base
sweeps. Alternate (ALT) channel switching is automatically
used in all other time deflection coefficient settings (200µs/
div - 20ns/div). In the latter case the active channel is switched
off and the previously inactive channel is switched on after
the completion of each time base sweep. To avoid
interference in chopped mode, or to make both channels
appear simultaneously visible, the actual setting (

ALT

CHP

)

displayed in the readout can be overwritten and changed to
the opposite mode. This is carried out by simultaneously
pressing and holding the

CHI (18)

and the

DUAL (19)

pushbuttons.

(26) A/ALT – B

Pushbutton for time base mode selection.

The instrument contains two time bases designated A and
B. With the aid of the B time base, signal parts displayed by
the A time base can be expanded in X-direction. The
expansion ratio depends on the time deflection coefficient
ratio of both time bases (e.g. “A: 100µs”, “B:1µs” = 100).
With higher expansion ratios the B time base trace intensity
reduces.

Each time the

A/ALT

pushbutton is briefly pressed, the time

base mode changes in the sequence A - alternate A and B -
A. The actual setting is displayed in the readout.

In A time base mode the

TIME/DIV. (25)

control knob is

operative only for this time base. The readout then only
displays the A time coefficient. The time base settings for
this condition are stored if the time base mode is changed.

ALT:

If alternate (A and B = ALT) time base mode is selected, the

TIME/DIV (25)

knob only controls the B time base switch or

vernier function. The alternate time base mode is a
subfunction of the B time base mode where both time base
traces are displayed. Consequently the readout displays both
time deflection coefficients (e.g. “A:100µs B:1µs”). Unlike
the former A time base mode, an intensified sector is also
visible on the A trace. This sector indicates the signal part
which is displayed by the B time base.
The intensified segment can be shifted horizontally by the

DEL. POS. (24)

control knob continuously (if the B time base

is operated in free run conditions). The difference between

the start of the A time base trace and the beginning of the
intensified sector shows the delay time. This information is
also displayed in the readout as an approximative value (e.g.
“

∆

t:2.5ms”) related on the calibrated A time coefficient

(uncalibrated e.g. “

∆

t>2.5ms”). The width of the segment

decreases when the B time coefficient is set to a lower value
(higher time deflection speed). For better reading, the vertical
position of the B trace position can be shifted (

please note

“TRS” (8)

Alternate time base mode causes the display to alter
between A and B time base after each sweep. In alternate
DUAL mode the sequence is channel I with A time base,
channel I with B time base, channel II with A time base and
channel II with B time base.
In alternate time base mode (A alternate B), the

X-MAG.

x10 (16)

function only effects the B time base and similarly

the readout.

Pressing and holding this button switches over from A or
alternate time base mode to B time base mode. If B time
base mode is selected, pressing and holding selects alternate
time base mode. Briefly pressing this button switches over
from B time base mode to A time base mode.
In B time base mode the display of the A trace(s), the
intensified sector(s) and the A time coefficient display in the
readout are disabled. As the trace separation

(TRS)

is no

longer required under this circumstances, this function is
switched off too. Consequently only the B time coefficient
is displayed by the readout.
When selecting alternate or B time base mode, the triggered
or free run state depends on the last chosen setting.

(27) DEL.TRIG. - VAR.

– Pushbutton with two functions.

DEL. TRIG.:

Each time the pushbutton is briefly pressed, the instrument
switches between free run (untriggered) and triggered B time
base, if alternate (A and B) or B time base mode is present.

The actual setting is displayed in the readout. Instead of the
approximate delay time (

“Dt:...”

) in free run mode, the

readout displays

“DTr: slope, DC (trigger coupling)”

triggered delay mode. In this mode, the former A time base
trigger settings regarding the trigger mode (automatic or
normal, -coupling, -slope and –level) are stored but still active.
W ith the activated delay trigger the instrument is
automatically set to normal trigger mode and DC trigger
coupling for the B time base. As the instrument contains a
separate trigger unit for the B time base, the trigger level

Controls and Readout

MADE IN GERMANY

A/ALT.

DEL.TRIG

TRS

PUSH
BOTH

PUSH
LONG

VAR.

CH I

CH II

DEL.POS.

ADD