HP 740B Operating And Service Manual page 41

Section V
Model 740B
CLIP - ON
DC MILLIAMMETER
hP428B
DC STANDARD/DIFFERENTIAL
[I~I]
VOLTMETER
hp
740B
@[
11~1
0
©
@
.
©
@ @ @ @ @ @ @
0
~@~
~~
0
OUTPUT CABLE
hp
1I055B
-SENSE
-@~+SENSE
~ ~+OUTPUT
20n
1
-OUTPUT
7"08 -8 -0763,t,
J
Figure 5-2. Current Limit Test
5-15. OUTPUT CURRENT AND CURRENT LIMIT TEST.
5-16. This test checks the maximum output current
(at least 50 rnA) and the range of the CURRENT
LIMIT control (5-50 rnA nominal). A 20
n
±1% 1/2 W
resistor (-hp- Part No. 0811-0305) and a clip-on dc
milliammeter (-hp- Model 428B Clip-On DC Milli-
ammeter) are required for this test.
a. Connect test setup shown in Figure 5-2.
b. Set 740B controls as follows:
c. The milliammeter should indicate 50 rnA or
greater.
d. Turn CURRENT LIMIT control fully ccw (MIN).
e. The milliammeter reading should decrease to
5 rnA or less.
5-17. LOAD REGULATION AND OUTPUT RE-
SISTANCE TEST.
- - - - N O T E - - - - -
OVERLOAD indicator will glow.
FUNCTION .
RANGE .
VOLTAGE SET . .
CURRENT LIMIT.
OUTPUT.
STD
10 V
1.50000
MAX
On
5-18. This test measures the no-load to full-load
output voltage excursion of the Model 740B. From
this voltage, the load regulation and output resistance
can be calculated. A 20
n
± 1% 1/2 W resistor (-hp-
Part No. 0811-0305), a 1 V ±0.0002% reference
supply (-hp- Model 735A DC Transfer Standard) and
a dc null detector (-hp- Model 419A DC Null Volt-
meter) are required for this test.
R
IV REFERENCE
SUPPLY
NULL DETECTOR
DC NULL
VOLTMETER
hp
419A
+SENSE OU U
DC STANDARD/DIFFERENTIAL
VOLTMETER
hp
740B
DC TRANSFE
@[
l[~l
0
~II@
STANDARD
@
.
hp
735A
@@@@@@@
@
+ -
0 0
II+~@:~II
,)
~D ~~~I
I I I I I ! I
I"='
OUTPUT CABLE
hp
1I055B
-OUTPUT~V--
-SENSE
20n[
±I"I.
'1':;:;;:
140e-S-080:5A
+ TP
T::.::A'-~
Figure 5-3. Load Regulation and Output Resistance Test
5-4 01794-1