SIR function editors 3-25
The voltage SIR function editor
Use the voltage SIR function editor is used to set up voltage selected ion
recording (VSIR) experiments.
VSIR is the most sensitive data acquisition mode, used for trace analysis. A
specified number of masses are monitored, by setting the magnet’s field
strength (B) to a fixed value and changing the accelerating voltage (V)
between values corresponding to the specified masses. The relationship
between the mass (m), B, and V is:
Hence, changing V from large to small values will scan from small to large
mass values. However, because the sensitivity drops when the accelerating
voltage is less than 4500 to 5000 volts, there is a limit on the mass range
obtainable using this technique. Typically, the maximum mass range over
which the optimum instrument sensitivity can be maintained is when the
maximum mass is equal to or less than 1.5 × the minimum mass.
To open the voltage SIR function editor:
In the MS method editor, click .
Alternative: Click Functions > Voltage SIR.
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