Global Specialties 1332A - Manual (Page 11)

9
OPERATING PRECAUTIONS
The power supply is ideally suited for virtually any type
of IC bread boarding from TTL, CMOS and ECL to
op-amps, audio and video amps, phase locked loops, and
microprocessor circuitry. However,certain normal bread
boarding precautions should be taken to avoid ground
loops and inadvertent loading. Observance of correct load
polarity is also important since most ICs may be damaged
by improper power supply connections.
POLARITY :
Observe proper polarity when connecting the power
supplies to the load, especially if the load is polarity
sensitive and does not have reverse polarity protection.
GROUND LOOPS :
A ground loop is a voltage drop on a ground bus caused
by a power stage output entering the ground bus some
distance away from the power supply ground binding post.
This small voltage drop, though only milliVolts or micro
Volts, is a part of the output load. If a preamplifier input of
circuit ground is connected to a portion of this ground bus,
feedback and oscillation may occur. To prevent this all
output stages should be positioned as close as possible
to the ground terminal,preamps farther away. Many audio
IC's have seperate input and output grounds to prevent
ground loops.
Eventhough power supplies are tightly regulated, a short
length of a power bus can present enough inductance to
cause linear IC oscillation at high frequencies. For this
reason, effective bypass capacitors are needed to bypass
the power buses. Place these capacitors as close as
possible to the power supply pins of the IC.Disc ceramics
(0.1µF ) work well and should be placed across as many
ICs as possible. Do not use elec trolytic or paper
capacitors because they have high inductances and cease
to act as bypasses above one or two MHz. Bypassing is
required with digital IC's also; problems such as inability
to reset or to clear and false triggering can occur if IC's are
not properly bypassed.
10
LOAD CONNECTIONS :
The load should be connected to the power supply output
terminals using separate pairs of connecting wires. This
will minimize mutual coupling effects between loads and
will retain full advantage of the low output impedance of
the power supply. Each pair of connecting wires should
be as short as possible and twisted or shielded to reduce
noise pick up. (If a shielded pair is used, connect one end
of the shield to ground at power supply and leave the other
end unconnected).
Positive or negative voltage can be obtained from this
supply by grounding either one of the output terminals or
one end of the load. Always use two leads to connect
load to the supply, regardless of where the set up is
grounded. This will eliminate any possibility of the output
current return paths through the power source ground
which would damage the line cord plug. This supply can
also be operated upto ±300V DC above ground, if neither
output terminal is grounded.
POWER SUPPLY OPERATION
INITIAL SET UP :
Refer to the preceding section for initial set up of the power
supply.
OPERATING INSTRUCTIONS :
Proper operation of most circuitry depends on correct
supply voltages. It is recommended that the power supply
be set to the required voltage levels with the load
disconnected. When the desired voltage is set (using the
variable voltage control),turn the AC power OFF, connect
the load to the power supply. then turn the AC power ON.
Output voltage and current of the power supply may be
read on the separate digital panel meters continuously.