- Last updated
Setting up ion‐gauge interlock
EC‐MS Technical Note #9
Checking and setting‐up external gauge and interlock
The external gauge is connected to the QMS via the analogue output. It has an identifier resistor, so it should be automatically recognized in PVMassSpec. The only requirement is that the gauge should be powered up before the QMS. The electronics box takes care of this with a time delay relay. How to set‐up and check the external pressure gauge:
Start PVMassSpec.
In the configuration pane of the QMS, the pressure from the external gauge should be written in the lower left corner; see Figure 1
Figure 1: Set the pressure from external gauge.
Click on the Configure button. Be aware, that the HPT200 gauge we are using is recognized as PBR260. Set up the mass spec to use external gauge and the units to mBar (see Figure 2).
Figure 2: Configure external gauge.
Set the external gauge as the reference pressure (see Figure 3).
Figure 3: Set external gauge as reference pressure.
Click on Set to set up the interlock (see Figure 4). A new pane opens where the interlocks and actions at certain pressures can be set (see Figure 5).
Set Trip High Action to Emission & EM Off and the setpoint to 5E‐5 (see Figure 5)
Figure 4: Enter interlock settings.
Figure 5: Interlock settings
Internal plate
The PrismaPro has a second option to protect the filament. In the ion source there is a plate measuring ion current (basically an ion-gauge). This has a set limit of 500 nA, which corresponds to approximately 5E-3 mbar. This is a factory-set limit that cannot be modified. However, this “gauge” must be calibrated as a standard maintenance procedure. For this, in PVMassSpec go to Sensor Maintenance > Calibrate Total Pressure. This is best done between 1E-6 and 1E-5 mbar (open to chip) and after the emission has been on for at least 10 minutes.