Output Noise Considerations; Programming Response Time With An Output Capacitor; Open Sense Leads - Agilent Technologies 6621A Operating Manual

OUTPUT TYPE
(40 W & 80 W)
LV Output CV Reg Error(mV) = Rs (
HV Output CV Reg Error(mV) = Rs (
CV Regulation Error = Remotely sensed voltage will change by this number of millivolts.
Rs = Resistance of each sense lead in Ω.
Vset = Programmed voltage value in volts.
Vdrop = Total drop in the load leads in volts.
In addition, include ±1 mV error per 200 mV drop in the -V load lead independent of Rs value.

Output Noise Considerations

Any noise picked up on the sense leads will appear at the supply's output and may adversely affect CV load regulation.
Twist the sense leads or use a ribbon cable to minimize the pickup of external noise. In extremely noisy environments it
may be necessary to shield the sense leads. Ground the shield at the power supply end only; do not use the shield as one of
the sensing conductors.
The noise specifications in Table 1-1 apply at the power supply output terminals when using local sensing. However,
voltage transients may be produced at the load by noise induced in the leads or by load current transients acting on the
inductance and resistance of the load lead. If it is desirable to keep voltage transient levels to a minimum, place an
aluminum or a tantalum capacitor, with an approximate value of 10 µF per foot (30.5cm) of load lead, right across the load
(see Figure 4-5). Refer to Figure 1-4 for capacitive load stability considerations.

Programming Response Time with an Output Capacitor

Because voltage programming into an external output capacitor may cause the supply to briefly enter CC operating mode,
voltage programming response time may be longer than that specified in Table 1-1. Use the following formula to estimate
the additional response time:
Additional (Added Output Capacitor)(Change in Vout)
=
Response Current Limit Setting
Time

Open Sense Leads

The sense leads are part of the supply's feedback path. Connect them in such a way so that they do not inadvertently
become open circuited. The power supply includes protection resistors that reduce the effect of open sense leads during
remote-sensing operation. If the sense leads open during operation, the supply returns to the local sensing mode, with the
voltage at the output terminals approximately 2.5% higher (low voltage outputs) or approximately 3% higher (high voltage
outputs) than the programmed value.
FORMULA
Vset Vdrop
- )
45 1.1
Vset Vdrop
-
)
105 3.3
Output Connections and Operating Information 51