HP 740B Operating And Service Manual page 16

Model 740B
3-11. DC STANDARD.
3-12. DESCRIPTION.
3-13. In Standard mode, the Model 740B amplifies an
internally generated reference voltage. The VOLTAGE
SET switches operate a voltage divider that varies
the reference supply output. The reference supply
output (0 to 1 V) is applied to the main loop amplifier
where it is amplified by 0 dB (1 V range), 20 dB (10
Vrange). 40 dB (1OOV range) or 60dB (1000 V range).
The gain of the amplifier is determined by the position
of the RANGE switch. The amplifier output voltage
(0-1000 V) is applied to the
+
and - OUTPUT terminals
when the. OUTPUT pushbutton/indicator is lighted.
The
+
and - SENSE terminals provide voltage feed-
back to the main loop amplifier and ensure proper
voltage regulation. The CURRENT LIMIT control
varies the maximum available output current. The
OVERLOAD indicator lights whenever the output cur-
rent exceeds the setting of the CURRENT LIMIT con-
trol. The ZERO control is used to zero the amplifier
output or to null out the effects of small external off-
set voltages. The output voltage is indicated directly
on the digital readout tubes (first five digits) and the
meter (sixth digit). The decimal point is automatically
placed.
3-14. OPERATING PROCEDURE.
3-15. To operate the Model 740B in Standard mode,
proceed as follows:
a. Set rear panel LINE VOLTAGE switch to cor-
rect position for available line voltage.
b. Connectacpowercordto ac power connector;
connect cord plug to ac line.
c. Turn on the Model 740B by depressing the
POWER pushbutton (indicator glows). Allow
the instrument to warm up for one hour.
d. Set FUNCTION to STD.
Section ill
f. Connect output cable assembly (-hp- Model
11055B) to OUTPUT Receptacle.
g. Connect output box terminals for the output
condition desired, using the information in
Table 3-1.
NOTE
1. Make sure all connections are
tight. Use insulated solid cop-
per wire for all leads. + and-
OUTPUT leads should be 20
gauge or larger.
2. Sensing is explained in Para-
graph 3-16.
3. Guarding is explained in Para-
graph 3-24.
4. Negative outputs are explained
in Paragraph 3-26.
h. Set RANGE to range nearest above desired
output voltage.
NOTE
1. The 1 mV, 10 mV and 100 mV
ranges are inoperative in STD
mode.
OVERLOAD indicator
will glow if these ranges are
selected.
2. OVERLOAD light may also
glow temporarily when RANGE,
FUNCTION orVOLTAGESET
controls are changed to indi-
cate temporary loop instability.
e. Check OUTPUT indicator. If glowing, depress
to turn output off.
i.
Set ZERO control for desired output zero re-
ference. (See Paragraph 3-31 for a detailed
discussion on using the ZERO control.)
Table 3-1. Output Terminal Connections
TYPE
CONNECT OUTPUT TERMINALS
OF
OUTPUT + OUTPUT - OUTPUT + SENSE - SENSE GUARD
4-
Local output, Directly Directly To
+
To - To - Not
unguarded to load to load OUTPUT OUTPUT
OUTPUT Connected
Remote output,
To load via To load via To load + via To"load - via To - Not
unguarded a test cable a test cable a test cable a test cable OUTPUT Connected
Local output, Directly Directly
To + To - To load
Not
guarded to load to load OUTPUT OUTPUT guard Connected
Remote output, To load via To load via
To load + via To load - via To load Not
guarded a test cable a test cable a test cable a test cable guard Connected
01794-1
3-5