Operation - TTI PL Serie Manuel D'instructions

Main Outputs
Setting Up the Output
With the power switch ON and the output switch OFF the output voltage and current limit may be
accurately set using the three output controls prior to connection to the load. The left hand meter
indicates voltage and the right hand meter indicates current.
With the output switch in the OFF (set) position, the current meter shows the value of the current
limit setting (indicated by all the decimal points coming on); with the output switch ON, it shows
the value of load current flowing.
Unless remote sensing is required the shorting bars should be placed from + sense to + output
and from - sense to - output. Ensure that the terminals are properly tightened before use.
Constant Voltage
The voltage output is set using the coarse and fine voltage controls; the current control sets the
maximum current that can be supplied.
Constant Current
If the load resistance is low enough such that, at the set level of output voltage, a current greater
than the current limit setting would flow, the supply will automatically move into constant current

operation.

The current output is set using the current limit control; the voltage controls set the maximum
voltage that can be generated.
Constant Current Indication
When the unit is operating in constant current mode, either by intention or because the current
limit point has been reached, the decimal points on the current meter will flash to indicate
constant current rather than constant voltage operation.
Instantaneous Current Output
The current limit control can be set to limit the continuous output current to levels down to 1 mA.
However, in common with all precision bench power supplies, a capacitor is connected across the
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.
Operation
9