HP 3478A Technical Manual page 25

3 3 4 78A 478A
Figure 3-5. Autoranging Points. Figure 3-5. Autoranging Points.
and a Fast trigger mode can be selected, but only over and a Fast trigger mode can be selected, but only over
the HP-IB (remote operation). When the multimeter is the HP-IB (remote operation). When the multimeter is
triggered, the right most digit on the display blinks triggered, the right most digit on the display blinks
(showing that the display is updated). The following (showing that the display is updated). The following
paragraphs explain the trigger modes. paragraphs explain the trigger modes.
3 3 - - 4 4 5 5 . . I I n n t t e e r r n n a a l l Trigger. Trigger.
measurement cycle is internally initiated and the 3478A measurement cycle is internally initiated and the 3478A
makes the measurements at the maximum reading rate. makes the measurements at the maximum reading rate.
The Internal Trigger is selected at instrument turn on or The Internal Trigger is selected at instrument turn on or
by pressing the INT/TRIG button. by pressing the INT/TRIG button.
3 3 - - 4 4 6 6 . . S S i i n n g g l l e T e Tr r ig igg g e e r r . In this mode, a measurement
cycle is initiated each time the SGL/TRIG button is cycle is initiated each time the SGL/TRIG button is
pressed. When the button is initially depressed, the pressed. When the button is initially depressed, the
3478A initiates a measurement cycle and then places 3478A initiates a measurement cycle and then places
the multimeter in the Single Trigger Mode. If the button is the multimeter in the Single Trigger Mode. If the button is
pressed during a measurement cycle (while in the Single pressed during a measurement cycle (while in the Single
Trigger mode), the 3478A starts a new measurement Trigger mode), the 3478A starts a new measurement
cycle. When the cycle is completed, a new cycle can cycle. When the cycle is completed, a new cycle can
then be initiated by pressing the Single Trigger button. then be initiated by pressing the Single Trigger button.
3- 3-47 47. . Exte ter r na Ex nal Tri l Trigg gger
pressing the SGL/TRIG button and operates the same pressing the SGL/TRIG button and operates the same
as the Single Trigger mode. The difference is that the as the Single Trigger mode. The difference is that the
3478A can be triggered from the External Trigger input 3478A can be triggered from the External Trigger input
on the rear panel. The input is TTL logic compatible and on the rear panel. The input is TTL logic compatible and
the trigger pulse should be at least l00nS wide. The the trigger pulse should be at least l00nS wide. The
3478A is triggered on the negative edge of the TTL 3478A is triggered on the negative edge of the TTL
pulse. pulse.
3 3 - - 4 4 8 8 . . Tr Tri i g g g g e e r H r Ho o l l d d . . In this mode, no triggering is
done by the 3478A (no measurement cycle is initiated). done by the 3478A (no measurement cycle is initiated).
This mode can only be selected using the 3478A's This mode can only be selected using the 3478A's
remote operation. remote operation.
3 3 - - 4 4 9 9 . . F F a a s s t T t Tr r ig igg g e e r r . . This trigger is the same as the
Single Trigger except the delays in the ACV and ACI Single Trigger except the delays in the ACV and ACI
Functions, and high Ohms Ranges are omitted. This Functions, and high Ohms Ranges are omitted. This
trigger can only be selected using the remote operation. trigger can only be selected using the remote operation.
When the 3478A is in the Single Trigger When the 3478A is in the Single Trigger
mode mode and an and an attempt
change change
In In this this mode, mode,
. In this mode, a measurement
er. . This mode is selected by This mode is selected by
In this mode, no triggering is
This trigger is the same as the
NOTE NOTE
attempt is is made made to to
range or function, the left portion of the range or function, the left portion of the
display goes blank (except for the display goes blank (except for the
decimal point) until another reading is decimal point) until another reading is
taken (instrument triggered). taken (instrument triggered).
3- 3-50 50. . SHIF IFTE SH
3 3 - - 5 5 1 1 . . G G e e n n e e r r a a l l
3-52. The Shifted Operation of the 3478A is used to 3-52. The Shifted Operation of the 3478A is used to
expand the capabilities of the multimeter using the same expand the capabilities of the multimeter using the same
number of front panel pushbuttons. This is done by using number of front panel pushbuttons. This is done by using
the bottom row of front panel buttons for two different the bottom row of front panel buttons for two different
operations, shifted and unshifted. An unshifted operation operations, shifted and unshifted. An unshifted operation
(AUTO/MAN, INT/TRIG, etc.) is normally selected by (AUTO/MAN, INT/TRIG, etc.) is normally selected by
pressing a single button. A shifted operation is done by pressing a single button. A shifted operation is done by
first pressing the blue "SHIFT" button (on the right end of first pressing the blue "SHIFT" button (on the right end of
the upper row of buttons) and then pressing one button the upper row of buttons) and then pressing one button
(on the lower row). To select a new shifted operation, (on the lower row). To select a new shifted operation,
press the blue Shift button again and the button for the press the blue Shift button again and the button for the
new operation. Table 3-1 new operation.
corresponding buttons. The shifted operations are also corresponding buttons. The shifted operations are also
the the
shown in blue lettering above the buttons. shown in blue lettering above the buttons.
3-53. 3. 3-5 When th the b When
"SHIFT" annunciator on the display is on. The "SHIFT" annunciator on the display is on. The
annunciator remains on until a different button is annunciator remains on until a different button is
pressed. pressed.
3- 3-54 54. . Nu Numb mber er Of
3-5 3-55. 5. The 3 The 3478
1/2, or 3 1/2 digits. The 5 1/2, 4 1/2, and 3 1/2 digits can 1/2, or 3 1/2 digits. The 5 1/2, 4 1/2, and 3 1/2 digits can
be selected by first pressing the blue Shift button and be selected by first pressing the blue Shift button and
then either the AUTO/MAN, then either the AUTO/MAN,
3-56. 6. 3-5 The The Num
reading rate of the multimeter. This is because the reading rate of the multimeter. This is because the
number of digits determines the integration time of the number of digits determines the integration time of the
A/D Converter. In the 4 A/D Converter. In the 4 1/2 digit mode, the integrat;k:.-
3-6 3-6
TM TM 11-6625-3071-1
TED O D OPE PERA RAT T IO ION N
Table 3-1 lists the shifted operations and lists the shifted operations and
e blue lue Shi Shift b ft butt utton on is p
Table 3-1. Shifted Operations Table 3-1. Shifted Operations
Of Di Digi gits ts Di Disp spla laye yed d
478A ca A can di n displ splay ay rea readin dings i
  or or   button, respectively. button, respectively.
Number ber Of D Of Digi igits ts Disp Display
1/2 digit mode, the integrat;k:.-
11-6625-3071-14 4
is pres ressed sed, t , the he
gs in ei n eithe ther 5 1 r 5 1/2, /2, 4 4
layed ed aff affect ects t s the he