Wayne Kerr AP10030, User & Service Manual

Page: 24 / 70

24 Wayne Kerr AP 1kW Power Supplies • Issue 2
Controlling The Output Current
The output current is controlled in the same way as the output voltage, except for the use
of different barrier strip connections. These are shown below:
3
3
4
4
5
5
6
6
7
7
8
8
9 10
Iprog Vprog Common
-S -S
Programming resistor 0 to 4k7
for zero to full scale current
3 - Voltage programme input
4 - Front panel control
5 - Constant current source
Fig 6.5.. Connections for resistive programming output current
To maintain the temperature coefficient and stability specifications of the power supply,
any resistors used for resistive programming should be stable types with low temperature
coefficients (60ppm per
°
C).
b) Remote Voltage Programming
Controlling The Output Voltage
6
6
7
7
8
8
9 10
Vprog Common
-S -S
6 - Voltage programme input
7 - Front panel control
8 - Constant current source
+ - Variable voltage source, 0 to 5V d.c.
preferably low source impedance
Fig. 6.6 Connections for voltage programming output voltage
Connecting up a variable voltage source as shown will programme the output voltage of
the power supply from zero to full scale for a 0 to 5V programming voltage.
A higher programming voltage can be scaled down using a potential divider.
Notes On Voltage Programming:
The voltage programming inputs, terminals 3 and 6,
have an input impedance of 5M
Ω
and will not significantly load most voltage sources.
The source impedance of the voltage programming source should be fairly low (in the
order of a few k
Ω to reduce noise pick up. Any noise voltage superimposed on the
programming voltage will appear as noise on the power supply output. Similarly, if a
resistor chain is used for scaling down a higher programming voltage, the resistor values
should be as low as practicable. If long voltage programming leads are used it is
advisable that they are twisted and screened.
Notes On Remote Programming: When using any of the methods of remote
programming described, the remote programming source replaces the front panel