HP 6268B Operating And Service Manual

by installing and adjusting R110 as discussed in paragraph
5-81 or, if the instrument is equipped with Option 020 or
022, by adjusting potentiometer R113 as discussed in
paragraph 5-83.
-CAUTION-
Do not allow programming terminals A2 or
—S to become open circuited while resistance
programming the output voltage. If they do
become open circuited, the supply's output
voltage tends to rise beyond its rated maximum.
If the supply's current controls and over¬
voltage crowbar trip point are properly adjusted,
however, no damage to the power supply or
load should result.
3-41 Constant Voltage Output, Voltage Input (Unity
Gain). The rear panel connections shown in Figure 3-5
allow the output voltage to be varied by using an external
voltage source to program the supply. In this mode, the
output voltage varies in a 1 to 1 ratio with the program¬
ming voltage. The load on the programming voltage source
is less than 20 microamperes. Impedance matching resistor
is required to maintain the temperature coefficient
and stability specifications of the supply. To adjust the
output voltage to exactly zero with a zero programming
voltage, follow the same instructions as are referred to in
paragraph 3-40.
3-42 Constant Voltage Output, Voltage Input (Variable
Gain). In the remote programming arrangement shown
in Figure 3-6, the series combination of external voltage
source Eg and reference resistor Rp replaces the supply's
internal voltage programming current source. As a result,
the voltage this external current source develops across
gain control R p becomes the output voltage of the supply,
and the gain relationship between Eg and the output volt¬
age equals the resistance ratio R p /Rp.
Figure 3-5. Voltage Programming of Output Voltage
(Unity Gain)
3-43 When using this programming technique, select
a value for Rp that is less than 10k ohms and that would
conduct at least 5 miiliamps if connected across the
programming voltage source with its voltage at the maximum
value of input voltage to be used. Once the value for R R
is selected, multiply Rp by the maximum voltage gain
desired to find R p . (If desired, the power supply's front
panel voltage controls can be used in place of external gain
control R p by deleting the external gain control from the
circuit and strapping together terminals A1 and A2.)
3-44 The output voltage of the supply can be adjusted
to exactly zero with a zero programming voltage input
either by installing and adjusting R111 as discussed in
paragraph 5-82 or, if the instrument is equipped with
Option 020 or 022, by adjusting potentiometer R11 2 as
discussed in paragraph 5-83.
3-45 Constant Current Output, Resistance Input. The
rear panel connections shown in Figure 3-7 allow the
output current to be varied by using an external resistor to
program the supply. The supply's constant current program¬
ming current, which is factory adjusted to 2.5mA ±10%,
determines the exact value of its programming coefficient.
The programming coefficients for the supplies included in
this manual are as follows:
Models 6259B 4 ohms/ampere
6260B 2 ohms/ampere
6261 B 4 ohms/ampere
6268B 6 ohms/ampere
6269B 4 ohms/ampere
If the ±10% accuracy of these coefficients is not adequate,
they may be adjusted either by changing resistor R30 as
discussed in paragraph 5-96 or, if the instrument is equipped
with Option 021 or 022, by adjusting potentiometer R116
as discussed in paragraph 5-97.
Figure 3-6. Voltage Programming of Output Voltage
(Variable Gain)
3-6

HP 6268B Specifications

General

Brand	HP
Model	6268B
Category	Power Supply
Language	English