Technical data

APPLICATIONS INFORMATION 71
Power Products Terms (cont’d)
Master-slave operation: a method of interconnecting two or
more supplies or electronic loads such that one of them (the
master) serves to control the others (the slaves). The outputs
of the slave supplies or inputs of the slave electronic loads
always remain equal to or proportional to the output of the
master. The outputs of the master supply and of one or more
slaves may be connected in series, in parallel, or with just
their negative or positive output terminals in common. (See
also “complementary tracking”). The inputs of the master
electronic load and one or more slaves may be connected in
parallel only.
Minimum transition time: the shortest possible time in which an
electronic load input can change from one level to another.
This is determined by the small signal bandwidth of the load.
Modulation: analog programming of the output voltage and/or
current. The output programming response time determines
the maximum slew rate at which the power supplies output
can be programmed.
Nominal value: the value that exists “in name only”; not the
actual value. For example, in the case of a power supply with
a calibrated output control, the nominal value is the value
indicated by the control setting. For a supply with a fixed
output, the nominal output is the output indicated on the
nameplate. The nominal value of a 120-volt ±10% line
voltage is 120 volts.
“One-Box”: a power supply that can be controlled by direct
connection to a computer (with no additional programmers)
and that can provide measured data to a computer without
external voltmeters or ammeters.
Output Impedance: at any frequency of load change,
∆Eout/∆Iout. Strictly speaking, the definition applies only for
a sinusoidal load disturbance, unless the measurement is
made at zero frequency (dc). The output impedance of an
ideal constant voltage power supply would be zero at all fre-
quencies, while the output impedance for an ideal constant
current power supply would be infinite at all frequencies.
Overcurrent protection: protection of the power supply,
electronic load and/or connected equipment against
excessive output current.
Overvoltage protection: protection of the power supply, elec-
tronic load and/or connected equipment against
excessive output voltage. Overvoltage protection is usually
by means of a crowbar protection circuit, which rapidly
places a low resistance shunt across the supply’s output
terminals to reduce output voltage to a low value if a
predetermined voltage is exceeded. A supply equipped
with an overvoltage crowbar must also be protected by
a means for limiting or interrupting the output current.
Peak-to-peak noise: is the range between maximum and
minimum noise level. Sometimes called noise “spikes.”
Peak-to-peak noise is typically low in energy and does not
show up in a RMS measurement, 20-20 Mhz.
Phase angle: specifies the time domain phase relationship
between two sine waves. The unit of phase angle is the
degree, with one cycle corresponding to 360 degrees of phase.
Programming speed: the maximum time required for the
programmed output voltage or current to change from a
specified initial value (usually zero or maximum output) to a
value within a specified tolerance band of a specified newly
programmed value (for most models 99.9% or 0.1% of
maximum output, respectively) following the onset of a step
change in an analog programming signal, or the gating of a
digital signal.
Readback: the ability of a power supply or electronic load to
measure its actual output voltage and/or current, and provide
the reading to a computer.
Remote Control: also referred to as “remote programming”.
Remote control is the setting of the power supply or
electronic load voltage, current, or other function by means
of an external control quantity such as a variable resistance,
voltage, or current, or by a digital signal from a computer.
Programming Speed Waveforms (height of overshoot and width of
tolerance band exaggerated)
Remote sensing: remote sensing, or remote error sensing, is a
means by which a power supply or electronic load monitors
the stabilized voltage directly at the load or source
respectively, using extra sensing leads. The resulting circuit
action compensates for voltage drops up to a specified limit
in the load leads.
Resolution: for a bench supply, the smallest change in output
voltage or current that can be obtained using the front panel
controls. For a system supply or electronic load, the smallest
change that can be obtained using either the front panel
controls, or a computer.
Reverse voltage protection: protection of the power supply or
electronic load against reverse voltage applied at the outputor
input terminals.
RI (discrete fault indicator/remote inhibit): a rear-panel port that
can be used to disable the power supply output independently
of the GPIB. This port can also be used to chain multiple
power supplies together such that an emergency shutdown of
one output automatically signals the other supplies to disable
their outputs.
(Constant – Voltage Operation)
Remote Control
Input Signal
Tolerance
Band
Tolerance
Band
Down-Programming Time
E
OUT
t
I
OUT
or
(Constant – Current Operation)
Up-Programming Time
100
10
0
10
1
10
2
10
3
10
4
10
5
10
6
10
7
10
1
0.1
0.01
0.001
Frequency - Hz
Impedence Ohms
Typical Output Impedence of a Constant Voltage Power Supply
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