Ametek Sorensen XEL 15-5, Operation Manual

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To change the current limit range the output must be switched off; if the output is on the warning
message
turn oFF is shown briefly in the display, the OUTPUT indicator flashes and the
range remains unchanged.
Constant Voltage
The output voltage is adjusted using the main 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 output voltage set, a current greater than the
current limit setting would flow, the power supply will automatically move into constant current
operation. The current output is adjusted by the CURRENT control and the VOLTAGE controls
set the maximum voltage that can be generated.
The CC indicator lights to show constant current mode.
Instantaneous Current Output
The current limit control can be set to limit the continuous output current to levels down to 1mA
(0.1mA on 500mA range). However, in common with all precision bench power supplies, a
capacitor is connected across the output to maintain stability and good transient response. This
capacitor charges to the output voltage and loading of the output will produce a current pulse as
the capacitor discharges which is independent of the current limit setting.
Current Meter Averaging
To reduce the measurement jitter with rapidly varying load
currents a 2-second time constant can be selected by pressing the
METER AVERAGE key; the indicator beside the key lights when
meter averaging is selected. Press the key again to CANCEL
meter averaging and return to the standard 20ms time constant.
Efficiency
The power supply minimizes dissipation by using electronic line frequency pre-regulation to
maintain a low overhead voltage to the output regulators. In addition, to optimize operation at
extremes of line input voltage and DC output power, the transformer secondary is intelligently tap-
changed by a relay. Hysteresis is used at the threshold point to prevent unnecessary switching
when the output is set at about that level. Apart from an audible ‘click’ the user will be unaware
that the relay has switched; there will be no disturbance on the output.
Programmable models use special transformers which do not require relay tap-changing.
Connection to the Load
The load should be connected to the positive (red) and negative (black) OUTPUT terminals. Both
are fully floating and either can be connected to ground.
Remote Sensing
The unit has a very low output impedance, but this is inevitably increased by the resistance of the
connecting leads. At higher currents this can result in significant differences between the
indicated source voltage and the actual load voltage (two 20m
Ω
connecting leads will drop 0.2V
at 5 Amps, for instance)
This problem can be minimised by using short, thick, connecting
leads, but where necessary it can be completely overcome by
using the remote sense facility.
This requires the sense terminals to be connected to the output
at the load instead of at the source; insert wires into the spring-
loaded SENSE terminals and connect directly to the load. Switch
the LOCAL/REMOTE switch to REMOTE.
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