Automatically Adjusting Npd Bead Voltage - Agilent Technologies 7820A Advanced User's Manual

5
Detectors

Automatically adjusting NPD bead voltage

92
Maximum Bead Voltage Display only. Shows the current
maximum bead voltage for the configured bead type (4.095 V for
ceramic beads).
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.
Detector off When the detector is off, Adjust offset and Bead
voltage are Off and initial Output is displayed.
Detector on—detector temperature less than 150 °C. When you
enter an Adjust offset value or press [On], detector gases turn on
and the display blinks the Temp not ready message.
Detector on—waiting for oven and/or detector to reach temperature
setpoint and equilibrium. If the oven or detector is not at
setpoint, the display continues to blink the Temp not ready
message.
Detector on—Dry Bead On If Dry Bead is On, the temperature rise
holds at 150 °C for 5 minutes to remove moisture, then
continues to the setpoint.
Detector on—during adjust offset. When the detector and oven
temperatures reach setpoint and equilibrate, the Adjust offset
process begins. The bead voltage is slowly increased until the
output is close to the Adjust offset value. The display blinks
Detector Slewing.
Advanced User Guide