Specifications

Detection Control Commands 6-41
SRS Residual Gas Analyzer
x It is good practice to readjust the Zero of the ion detector every time the type
of detector (FC or CDEM) is changed. This is particularly important if the
new detector settings have not been used in a long time or since the unit was
turned on or recalibrated with the CL command. See the CA command for
details and more recommendations.
Parameters:
HV0: Use this parameter value to “turn off” the Electron Multiplier and enable
Faraday Cup (FC) Detection. The following steps are taken:
x The biasing voltage of the CDEM is set to Zero (i.e. no ion collection and no
gain).
x The electrometer is connected to the FC signal output and reconfigured to
measure positive currents.
x The firmware algorithms are reconfigured to transmit the magnitude of the
positive currents measured.
x The HV_LED is turned off.
x The STATUS Byte is sent out to prompt the end of the command
HVparam, param: 10-2490: The parameter is the magnitude of the CDEM bias
voltage requested (the actual biasing voltage is negative). The following steps are
taken:
x The requested biasing voltage is set on the CDEM.
x The electrometer is connected to the CDEM anode and reconfigured to
measure negative currents.
x The firmware algorithms are reconfigured to transmit the magnitude of the
negative currents measured.
x The HV_LED is turned on.
x The STATUS Byte is sent out to prompt the end of the command
HV*: The command is excecuted with the default parameter value.
Default: 1400 (Volts)
HV?: Returns the magnitude of the biasing voltage on the CEM.
The number returned by the query command is the actual voltage available at the
output of the HV driver and will always be very close but rarely identical to the
one requested with the HVparam command.