HP 740B Operating And Service Manual page 24

Model 740B
3-60.
AMPLIFIER.
3 -61. In the Voltmeter and Differential Voltmeter
modes of operation, the Model 740B may be used as
a power and voltage amplifier. Two separate ampli-
fier outputs are available.
3 -62. POWER AMPLIFIER.
3-63. DESCRIPTION.
3 -64. Whenever an input voltage is applied to the
Model 740B in Voltmeter or Differential Voltmeter
modes, a voltage is present at the + and - OUTPUT
terminals when the Output is turned on. This voltage
is equal to the input voltage on the 1 V range and above.
Output voltage on the millivolt ranges exceeds the
input voltage by 20 dB, 40 dB or 60 dB onthe 100 mY,
10 m V and 1 m V ranges respectively (Table 3 -6).
Output current characteristics are the same as Stan-
dard mode; the high input resistance characteristics
of the Voltmeter and Differential Voltmeter modes are
retained. When used as a power amplifier in Volt-
meter mode, up to 110% of range may be applied to
and obtained from the Model 740B with no loss of gain
accuracy.
Table 3-6. Power Amplifier Output Voltage
VOLTAGE
OUTPUT VOLTAGE
RANGE
(With full scale input
GAIN
applied)
1000 V OdB
1000 V
100
V
OdB 100 V
10 V
OdB lOY
1
V
OdB IV
100mV +20 dB IV
10 mV
+40 dB IV
1 mV +60 dB
IV
Section III
3-65. OPERATING PROCEDURE.
3-66. To use the Model 740B as a power amplifier,
proceed as follows:
a. Turn on the Model 740B and allow one hour
for instrument warmup.
b. Set FUNCTION to
~VM
or VM as desired.
c. If measurement of input voltage is desired,
perform steps e through
l'
of Paragraph 3-46
for ~ VM position or e through
j
of Paragra ph
3 -59 for VM position. If measurement of in-
put is not desired, set RANGE to the range
nearest above the input voltage.
d. Check OUTPUT pushbutton-indicator. If
glowing, depress to turn Output off.
e. Connect Output Cable (-hp- Accessory 11055B)
to Output Receptacle.
f. Connect OUTPUT terminals for the output
condition desired (Table 3-1).
g. Set CURRENT LIMIT control for the desired
maximum limit of output current (Paragraph
3-38).
h. Depress OUTPUT pushbutton indicator. Indi-
cator lights to indicate dc output. OVERLOAD
indicator, if glowing, indicates the current
limit has been exceeded or no remote or local
sensing is in effect.
3-67. VOLTAGE AMPLIFIER.
3-68. DESCRIPTION.
3-69. The rear panel RECORDER OUTPUT terminals
provide a dc voltage which is proportional to meter
Table 3-7. RECORDER OUTPUT Voltage Gain as a Function
of RANGE and SENSITIVITY
SENSITIVITY
RANGE
Xl X10 X10
2
X10
3
X10
4
1000
V
-60 dB -40 dB - 20 dB OdB + 20 dB
100 V
-40 dB -20 dB OdB + 20 dB + 40 dB
10
V
-20 dB
o
dB + 20 dB + 40 dB + 60 dB
1 V
o
dB +20 dB + 40 dB
+ 60 dB + 80 dB
100 mV +20 dB +40 dB
+ 60 dB + 80 dB + 100 dB
10 mV +40 dB
+60 dB + 80 dB + 100 dB + 120 dB
1 mV +60 dB +80 dB + 100 dB
+ 120 dB +140dB*
* Not recommended
01794-1
3-13