What Is a Frequency Discriminator?
A frequency discriminator is a circuit and device that cuts the noise portion of an electrical signal.
This device can also convert frequency variations into corresponding amplitude changes, which is a fundamental principle in FM radio broadcasting.
When plotted with input frequency on the horizontal axis and output voltage on the vertical axis, the characteristic curve of a frequency discriminator resembles an ‘S’ shape.
Each frequency discriminator value can be set from 0V to 10V in 0.01V increments. It can also be turned off if necessary.
Uses of Frequency Discriminators
A frequency discriminator is used to exclude noise from the actual measurement result, such as in detection systems for abnormalities in manufacturing and detection systems for samples with minute changes in research and development.
For example, in manufacturing, it is used in systems to detect standard arc welding in welding spatter. In biochemical research, flow cytometers use frequency discriminators to evaluate cells and bacteria, avoiding the output of unwanted cell fragment information.
Principles of Frequency Discriminators
The discriminator can be set to any voltage pulse. When the voltage of the set voltage pulse exceeds the exclusion threshold, the voltage pulse is captured by an analog-to-digital converter and converted into a numerical value. Typically, there are eight different voltage settings. If none of the set values exceed the exclusion criteria, it is judged as noise, and no data is captured.
When used in a flow cytometer, cells other than those to be evaluated may be present. To avoid detecting such cells, it is necessary to set voltage pulses specific to the substance to be measured.
In FM demodulation, the discriminator plays a crucial role by converting frequency variations of the radio wave into amplitude changes, which are then processed to retrieve the original audio signal.