# Frequency Display Format Selector

The frequency display format selector allows you to choose how to plot the frequency data.

## Raw Frequency

In raw frequency mode, the data is displayed as the actual frequency reading from the QCM200. This is a number in Hertz (Hz), and will be near 5 MHz (5,000,000 Hz).

## Relative Frequency

This mode allows you to plot the data as a frequency shift from a reference point. That is, the frequency is plotted relative to a reference frequency which you set via the Zero Rel F button.
Note that when the software begins data acquisition, the first frequency read from the QCM200 is treated as the reference frequency until you set a new reference frequency. See the help entry on Zero Relative Frequency for more details.

## Relative Mass

Sometimes you wish to know how much mass was gained or lost at the probe. The quartz cystal used in the probe will shift down in frequency by 56.6 Hertz for every microgram (ug) per square centimeter (cm2) that is bound to its surface. This constant is known as Cf. Given this information, the software calculates the change in mass by looking at the change in relative frequency. The answer is in ug/cm2, so you must normalize to the active area of the probe. See the QCM200 manual for full details.
Note that when the software begins data acquisition, the first frequency read from the QCM200 is treated as the reference frequency for the mass calculation until you set a new reference frequency. See the help entry on Zero Relative Frequency for more details.