Technical data

117
Applications Information ac Power and Load Connections(Continued)
Power Products Catalog 2002-2003 For more detailed specifications see the product manual at www.agilent.com/find/power
Agilent Technologies
Making the Sensing Connections
STEP 8. Remove the jumper connections
between the power supply sensing and
output terminals, and connect the power
supply sensing terminals to the dc distri-
bution terminals as shown in Fig. 12.
Figure 12
Properly Grounded Power Supply System with
Remote Error Sensing
Use an insulated shielded pair for
the sensing leads. Do not use the
shield as one of the sensing conduc-
tors.
STEP 9. Connect one end of the sensing
lead shield to the dc common point and
leave the other end unconnected.
In nearly all cases this method of
connecting the sensing shield mini-
mizes ripple at the dc distribution
terminals.
Protect Against Open Sensing
Leads Step
STEP 10. Avoid the possibility of an open
remote sensing path, either on a long-
term or a transient basis.
Opening a sensing lead causes the
power supply output voltage to
increase. Protective circuits in the
supply provide some load protection
by limiting the amount of the
increase, but eliminating all switch,
relay, or connector contacts from
the remote sensing path helps to
minimize the possibility of any loss
of regulation due to this cause.
Check the Load Wire Rating
STEP 11. Verify that the voltage drop
in the load leads does not exceed the
capabilities of the remote sensing circuit.
Most well regulated power supplies
have an upper limit to the load lead
voltage drop around which remote
sensing can be connected without
losing regulation. This maximum
voltage drop is typically 0.5, 1, or 2
volts, and may apply to the positive,
the negative, or both the positive
and negative output leads. See the
instruction manual for the exact
load lead voltage drop limitations
of a particular power supply.
Remember too, that any voltage
drop lost in the load leads reduces
the maximum voltage available for
use at the load. Either of these limi-
tations sometimes dictates the use
of a larger wire size than would be
required by wire current rating or
impedance considerations.
Check for Power Supply Oscillation
STEP 12. Verify that the power supply
does not oscillate when remote sensing
is connected.
Although dc and low frequency per-
formance are improved by remote
sensing, phase shifts associated with
long load and sensing leads can
affect the stability of the feedback
loop seriously enough to cause
oscillation. This problem can
frequently be corrected by readjust-
ing a “transient recovery” or “loop
stability” control inside the supply if
the circuit includes one; follow the
adjustment procedure in the manual.
Another remedy that is often effec-
tive is to disconnect the output
capacitor inside the power supply
(some models have a rear panel
jumper that can be removed for this
purpose) and to connect a similar
capacitor across the dc distribution
terminals.
Check for Proper Current Limit
Operation
STEP 13. Check that the operating point
of the current limit circuit has not been
affected by the remote sensing
connections.
With some power supply designs,
the resistance of one of the output
conductors adds to the resistance
used for current limit monitoring
when remote sensing is used. This
reduces the threshold value at which
current limiting begins and makes
readjustment of the current limit
Power Supply
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Load
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DT and CP
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Load
No. 2
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