VICI D-4-I - Manual (Page 11)

7
ZERO push button
Offsets the output signal to zero volts by a measurement of the standing
current. The offset is applied to the output when the button is released.
Once set, the offset is not changed unless the unit is re-zeroed or the mode
is changed. To remove any applied offset and restore the unit to an un-
zeroed condition, toggle the
MODE or RANGE switch. The function of this
control is duplicated by an external logic connection; see UNATTENUATED
OUTPUT below.
Display
Indicates standing current in the PDHID mode or bias voltage in the PDECD
mode, auto-scaled to the most suitable range. In the un-zeroed PDHID
mode, the display indicates the instantaneous signal current in nA. After
zeroing, the display indicates the standing current by which the signal is
offset. In the PDECD mode, the display indicates the controlling bias
voltage unless the
CURRENT switch or ZERO button is pressed, when
it indicates the set current.
ATTENUATED OUTPUT connector
Normally connected to a strip chart recorder. This output has an unatten-
uated range of 0 - 10V, and an internal signal reference (-) at zero volts. For
best noise performance, the shield (earth) and signal reference (-) should
not be connected together. The signal from this output is scaled by the
attenuation factor set on the front panel.
UNATTENUATED OUTPUT connector
Normally connected to a data acquisition system or other recording means.
For convenience, a full-scale 0 - 10V output and a 1/10 scale 0 - 1V output
are provided, with an internal signal reference (-) at zero volts. For best
noise performance, the shield (earth) and signal reference (-) should not be
connected together. The internal impedance of these outputs is 1000 ohms.
The connection marked
ZERO is a low-true, 5V logic-level input which
duplicates the function of the front-panel ZERO; connection of this input to
COM through either a relay contact or logic gate is equivalent to pressing
the
ZERO button.
HEATER OUTPUT connector
For connection to the detector heating system.
ELECTROMETER INPUT cable
For connection to the collector electrode of the PD detector. The full-scale
input current is determined by the
RANGE switch. Input voltages in excess
of 15 VDC may result in damage to the electrometer.
BIAS A, B OUTPUT cables
For connection only to the bias electrodes of the PD detector in the manner
described on page 16 under the heading “Electrical Connections”. These
outputs supply high voltages when power is applied to the unit, and caution
should be observed when connecting or disconnecting these cables.
NOTE: These terminals are for connection only to
equipment having no accessible live parts. Insulation
of external circuits to which these are connected must
meet the requirements of EN61010 for 220 VDC working
voltage.
Introduction