VICI D-2-I - Manual (Page 11)

7
TEMPERATURE control and indicator
Sets the temperature (°C) of the detector heater block. The indicator is
steadily on when maximum power is being applied to the heater, steadily off
when no power is applied, and regularly blinking on/off when the set tem-
perature has been established.
Note that due to the fail-safe mechanism designed into the temperature
controller, the heater will not operate if mains power is applied before the
heater is connected or if the detector is too cold (< 0°C). If the heater is
disconnected with mains on, the unit must first be turned off to restore
control of the heater; if the unit is operated in a very cold environment, the
detector should first be gently warmed without power applied.
The fail-safe mechanism will also act under any condition resulting from loss
of control (e.g., over-heating, RTD failure, etc.). If proper procedures have
been followed and the controller will not heat the detector, there is cause to
suspect that the fail-safe mechanism has been activated. Consult the
factory or an authorized representative. Note that the maximum temperature
for operation of the PD-D2-IS is 400°C.
Heater control may be lost during periods of fast
electrical transients. The unit will self-recover.
MODE switch
Determines the operational mode of the controller and unzeroes the signal
output (see discussion under ZERO push button). This switch changes the
bias voltages supplied to the electrodes as required for each detection
mode. In the PDHID mode the bias voltages are set at -200 and the
linearization circuit is inactive; in the PDECD mode the bias voltages are
internally controlled and the detector output is linearized. (Note that the
D-2-I cannot operate in the PDECD mode.)
RANGE switch
Determines the full-scale range of the electrometer: 100 nA @ 1X, or 10 nA
@ 10X. In PDECD mode, the high detector background current normally
restricts operation to the 1X range.
CURRENT switch
Sets the standing current in PDECD mode. Pressing at the top increases
the current, pressing at the bottom decreases the current.
ATTENUATION control
Determines the attenuation factor for the recorder output.
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.
Introduction