Hameg HM504-2 Manual Download Page 20

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Subject to change without notice

Readout (e.g. “10 µs”). Depending on the time base mode
the following ranges are available without taking X x10 into
account.

Undelayed: 500 ms/div – 50 ns/div.

The following (principle) values depend on the time base
setting in undelayed mode, as the undelayed time base
always has to have the higher coefficient.

Search (“sea”): 20 ms/div – 100 ns/div.

Delay (“del”): 20 ms/div. – 50 ns/div.

Triggered after delay (“dTr): 20 ms/div – 50 ns/div.

VAR.:

The vernier (variable) function is described under item Z ON/
OFF VAR

[24].

[23] DEL.MODE ON/OFF

–

Pushbutton with two functions.

ON/OFF function:

Pressing and holding this pushbutton switches over between
delayed and undelayed time base mode. The actual setting is
indicated by the READOUT. The delayed time base operation
enables a magnified display in X direction which is otherwise
only possible with a second time base.

a) Undelayed time base mode.

If on the right of the trigger READOUT information (source,
slope, coupling) neither “sea”, “del” nor “dTr” is indicated,
undelayed time base mode is present.
Note: When the intensity modulation function is switched
on, the letter “Z” is visible in this position on the screen.

b) Delayed time base mode.

Is indicated by the READOUT showing “sea”, “del” or
“dTr”. If intensity modulation was chosen before switching
over to delay time base mode, this function is automatically
switched off and consequently the letter “Z” deleted.

Switching over from undelayed to delayed time base mode
automatically selects “sea” (search) mode. Briefly pressing
the pushbutton then opens a Pulldown menu for operating
mode selection. Please note “B: Menu Display and Opera-
tion”.
The following description assumes that in undelayed time
base mode the trace starts at left edge of the graticule, with
x10 X MAG

switched off.

Functions

“sea”:

SEARCH

mode, the holdoff time is automatically set to

minimum and for the first few divisions the trace is blanked.
The point at which the trace is unblanked can be varied with
the

DEL.POS [21]

control (fine adjustment) from about 2 to

7 divisions. The blanked section serves as a guide to the
delay time. The delay time is based on the current time
deflection coefficient setting and can also be coarsely set
with the

TIME/DIV

control (range: 20 ms to 100 ns).

The signal position at which the unblanking occurs marks the
trace start position which is present after switching over
from “sea” to “del”. This enables lower time deflection
coefficient settings for signal expansion.

“del”:

DELAY

mode, a trigger event does not start the trace at

once but only initiates the delay time. After the delay time has
elapsed the trace is started. Selecting lower time deflection
coefficients (higher time base speed) cause a signal expansion
in X direction.
The

DEL.POS [21]

control can still be used for correcting the

signal start position affected by the TIME/DIV setting.

Note:

With higher expansion rates the trace intensity may

reduce drastically.

“dTr”:

In triggered

DELAY

mode the first trigger unit, used for

triggering in undelayed time base mode, starts the delay time
as in “del” mode. After the delay time has elapsed the delay
time base must be triggered by the second trigger unit, to
start and unblank the trace. The latter requires suited
instrument settings (LEVEL

, SLOPE

) to enable triggering.

Note:

The trigger indicator LED (TR)

[10]

only indicates the

trigger condition of the first trigger unit. It may be lit although
the trigger conditions for the second time base are not met
and the trace remains blanked.

As in “del” mode the

DEL.POS [21]

control can still be used.

In contrast to complex signals the effect of this function may
not be noticed with simple repetitive signals as the trigger
point ‘hops’ from cycle to cycle, each being the same.

[24] Z ON/OFF VAR.

– Pushbutton with two functions.

Z ON/OFF:

Briefly pressing the pushbutton switches over the function
of the TRIG.EXT. BNC-socket

[30]

from external trigger input

to intensity modulation input and vice versa. In connection
with external triggering, delay time base (“sea”, “del” or
“dTr”) and “Component Tester” mode, Z modulation can not
be enabled.

Z modulation is shown on the READOUT to the right of
“trigger source, slope and coupling” indicated by the letter
“Z”. High TTL level (positive logic) gives blanking, dark, low
level gives unblanking, bright. No higher voltages than +5
Volt are permitted.

VAR.:

Pressing and holding the button changes the function of the

TIME/DIV. -

knob

[22]

from time deflection coefficient switch

to time vernier (fine adjustment) control and vice versa.

Controls and Readout

Y-POS / CURS.I

VOLTS / DIV.

CH I

CH II