Automatically Adjusting Npd Bead Voltage - Agilent Technologies 7890 Series Advanced Operation Manual

5
Detectors

Automatically adjusting NPD bead voltage

196
Auto Adjust Bead Recommended On. When On, the automatic
adjust offset process starts when the bead reaches the
temperature setpoint after having been turned off or cooled
below 150 °C. Auto adjust starts after Dry Bead hold time, if
enabled. Auto Adjust Bead uses the adjust offset feature to
protect the bead—especially new beads—by making sure that
the desired offset is obtained with the lowest possible bead
voltage. When Off, the bead voltage will rise as soon as the
Dry Bead time elapses, or as soon as the temperature
setpoint is reached if Dry Bead is off.
Dry Bead Recommended On. When On, the bead temperature
holds at 150 °C for 5 minutes before continuing to the
setpoint. This allows any condensation to evaporate and be
swept out of the detector.
Blos Bead If using a Blos bead, set to On. For ceramic
beads, set to Off. The Blos Bead On setting restricts the
allowable bead voltage to the range appropriate for this
bead.
Maximum Bead Voltage Display only. Shows the current
maximum bead voltage for the configured bead type (4.095 V
for ceramic beads, 1.1 V for the Blos bead).
Agilent recommends using the Adjust offset feature to
automatically determine the lowest bead voltage needed to
give the desired response.
When the detector is turned on, the temperature rises at a
controlled rate.
• If Dry Bead is On, temperature holds at 150 °C for 5
minutes to drive off moisture, then continues to the
setpoint.
• If Dry Bead is Off, the temperature rises directly to the
setpoint.
When the temperature reaches the setpoint, the Bead Voltage
gradually rises until it produces the desired output.
Adjust offset
When you enter a value here, or press [On/Yes] to use the
stored value, detector gas flows turn on, the bead heats, and
the bead voltage adjusts until Output is stable and equal to
the entered value. There are five stages of Adjust offset.
Advanced Operation Manual