Current Limit - TTI PL-P Serie Manuel D'utilisation

output (isolated by the output switch) to maintain stability and good transient response. This
capacitor charges to the output voltage, and short circuiting of the output will produce a short
current pulse as the capacitor discharges which is independent of the current limit setting.
Current Meter Damping
The digital meters have a reading rate of about four readings per second and a damping time
constant of 20 ms, thus providing virtually instantaneous response to reading changes.
If the unit is used to supply a load varying at a rate faster than about 0·5Hz, difficulty may be
experienced in interpreting the current meter readings. This problem can be alleviated by
pressing the button marked DAMPING. This increases the current meter damping time constant
to 2 seconds with the result that the meter will tend to read the average current flowing rather
than following the variations. This facility should only be used when necessary since it greatly
increases settling time and reduces absolute accuracy.
Series or Parallel connection with other units
The output of the power supply unit is fully floating and may be used in series with other power
supply units to generate high DC voltages up to 300V DC.
WARNING! Such voltages are exceedingly hazardous and great care should be taken to shield
the output terminals for such use. On no account should the output terminals be touched when
the unit is switched on under such use. All connections to the terminals must be made with the
power switched off on all units.
It should be noted that the unit can only source current and cannot sink it, thus units cannot be
series connected in anti-phase.
The unit can be connected in parallel with others to produce higher currents. Where several units
are connected in parallel, the output voltage will be equal to that of the unit with the highest
output voltage setting until the current drawn exceeds its current limit setting, upon which the
output will fall to that of the next highest setting, and so on. In constant current mode, units can
be connected in parallel to provide a current equal to the sum of the current limit settings.
Application of an external voltage source to the output
In common with all series regulated single-ended power supplies, the unit is not capable of
sinking current provided from an external source.
If a voltage greater than the set output voltage of the unit is applied from an external source, the
internal regulator will turn off, no current will flow, and the voltage meter will read the applied
voltage. No damage will result providing the applied voltage does not exceed the maximum
output voltage of the power supply by more than 20 Volts. Application of a voltage greater than
this is prohibited.
If a reverse voltage is applied, this will be clamped by an internal reverse protection diode. The
reverse current should not exceed 3 Amp.
Logic Supply
Setting the Output
Set the output with the calibrated control. With the output switch OFF the meter displays voltage;
with the switch ON it displays load current. Unless remote sensing is required the shorting bars
should be placed from + sense to + output and from - sense to - output.

Current Limit

Current limit is indicated by all the decimal points flashing and is set by a calibrated control with a
range of 0·1A to 7A. The power supply is not designed to operate in constant current mode as a
current source.
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