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3-69
Determining the Value for Rx. Each slave supply
has an external resistor Rx associated with it that supplies
its voltage programming current. If the temperature
coefficient and stability specifications of the supplies are
to be maintained, these must be stable, low noise resistors
with a temperature coefficient of less than 30ppm per °C
and a power rating at least 30 times what they will actually
dissipate. To calculate the proper value for Rx for each
slave, the following information is required:
a. Ep^, the rated maximum voltage of the master supply
b. Eg, the corresponding maximum voltage desired of
the slave supply with its voltage control set to maximum.
c. Rp, the resistance of the slave supply's coarse
voltage control.
The Rp values for the supplies included in this manual are
as follows:
Model
6259B, 6260B
2.5k£2
6261B
5kft
6268B, 6269B
lOkft
To find Rx use the formula:
Rx
= (Em rp/es> ~rp
For example, if the slave supply is a Model 6259B and we
want its output to vary from zero to 10 volts as the master
supply varies from zero to 40 volts, the solution for Rx is:
Rx = (40V x 2.5kf2/10V) - 5kft
Rx = 5kf2
3-70
It is also possible to make an auto-tracking slave's
voltage equal the output of the master supply. To do this,
make a direct connection from the +S terminal of the
master to the A2 terminal of the slave instead of using
a programming resistor, and remove the slave's A1 to A2
jumper.
3-71
Setting the Voltage and Current Controls. The
voltage control of each slave must be set fully clockwise to
obtain the voltage ratios established by the formula for Rx
given in paragraph 3-69. By lowering the settings of the
slave's voltage controls, the voltage of the slave can be
made a smaller percentage of the master supply's voltage.
The current controls of all supplies in an auto-tracking
combination are independently operative and can be used
to set current limits for each individual load. If the master
supply goes into constant current mode, the output voltages
of the slaves continue to track that of the master. If a slave
supply goes into constant current mode, however, no other
supply is affected.
3-72
Overvoltage Protection in Auto-Tracking. Parallel¬
ing the crowbar circuits, as is required for the auto-parallel
and auto-series modes, is optional in the auto-tracking
mode. If the external trigger windings of transformer T90
in the master and in the slave supplies are not paralleled,
the overvoltage protection circuit in each supply indepen¬
dently monitors the voltage across its own load. Then if
the master supply crowbars, the output voltage of the slave(s)
also decreases, but if one of the slaves crowbars, no other
supply is affected.
3-73
In order to have all supplies in an auto-tracking
combination crowbar simultaneously if any of them has
an overvoltage condition, parallel their crowbar circuits as
shown in Figure 3-14 or 3-1 5.
Set the overvoltage poten¬
tiometer in each supply so that it trips at a point slightly
above the voltage that supply will provide.
3-74
Auto-Tracking With Remote Sensing. To combine
auto-tracking operation with remote sensing, connect the
supplies as described above but remove the +S and —S
jumpers from each supply and connect the +S and —S
terminals directly to the (+) and (-> ends of its load.
Observe the precautions outlined under paragraph 3-27.
3-75
Auto-Tracking With Remote Programming. When
two or three supplies are connected for auto-tracking opera¬
tion, their output voltages can be remotely programmed but
their currents cannot. Refer to the appropriate sections of
paragraph 3-34 for the additional rear panel connections
required and make these connections to the master supply
only. Observe all precautions outlined in the paragraphs
on remote programming. The simultaneous use of remote
sensing and remote programming is also possible during
auto-tracking operation.
EXT
CROWBAR
TRIGGER
/+
^ AI
A2
A3
A4
A5
A6 A7
A8 +S -S
A9
Figure 3-14. Auto-Tracking Operation of Two Units
3-11
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