Ametek Sorensen XEL Serie Mode D'emploi page 23

OVP and OCP
OVP (over-voltage protection) and OCP (over-current protection) are implemented in firmware and
can only be set and used when under remote control via the RS232, USB, LAN (LXI) or GPIB
interfaces. Setting resolutions are 10mV and 1mA and typical response times are 500ms.
However, in local mode, OVP and OCP are still active but automatically default to 105% of the
instrument's range maximum. This usefully provides shut-down protection in the event of prolonged
application of a CV or CC control voltage which attempts to set the output beyond 105% of the
range maximum.
Practical Considerations when using CV and CC
The stability of the control voltages directly affects the stability of the output. Any noise on the
control signals will generate noise on the output. To minimize noise on the output connect the
control voltages to the CV, CC and RTN inputs using twisted or screened pairs (screens grounded
at one end only) and keep the connections as short as possible. Note that output noise is inherently
slightly higher when analog remote control is used because of intrinsic noise in the isolating input
circuitry, see the Specification.
The diagrams below show the connections for Constant Voltage (CV) and Constant Current (CC)
control using an external voltage.
Note that when the OUTPUT is on, the instrument's display always shows the actual output voltage
and current, whichever control source is active. However, when the OUTPUT is off, the display will
show the preset voltage and current set by the front panel controls (or the digital interface if active)
and not the values determined by the CV and CC inputs even if they have been made active (CV
and CC set to Remote). To avoid confusion it is good practice to set the front panel controls to
minimum when remote CV and CC are used.
Constant Voltage Control
Constant Current Control
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