HP 54620A, User'S And Service Manual

Page: 55 / 243

To change the logic threshold for input signals
1
Press
Logic Levels
.
2
Press the
Set
softkey to highlight the range of channels for which
you want to set the logic threshold.
Ranges available are
Chan 0-7
(channels 0 through 7),
Chan 8-15
(channels 8 through 15), and
TRIG IN
(the external trigger input).
3
Press
TTL
,
CMOS
,
ECL
, or
User
to select the threshold.
4
If you selected
User
, set the threshold voltage using the Entry knob.
Turning the Entry knob while in this menu automatically sets the Threshold
option to
User
.
5
Repeat steps 2 through 4 for each group of channels for which you
want to set the threshold.
You can exit the threshold setting menu by pressing any other front-panel
key.
The threshold voltage setting is used by the input comparators to determine
whether an input signal is a logic low or logic high. The settings for each
option are shown in table 2.
Table 3 Threshold Voltage Settings
Option Voltage
TTL 1.50 V
CMOS 2.50 V
ECL -1.30 V
User Continuously variable from –6.00 V to +6.00 V
Making Analyzer Measurements
To change the logic threshold for input signals
54