What does it mean 1Hz cut-off frequency

[naseeam]

If someone says, we are filtering these inputs (approximately 1 Hz cut-off frequency), What does that mean? What's cut-off frequency?

The input is Thermistor Sensor. The hardware circuit reads the resistance from the input and provides it to the software. There are Eight Inputs. Software gets the resistance from all 8 channels every 20 ms. Software is filtering these inputs(approximately 1 Hz cut-off frequency). What does that mean? Please provide tutorials etc. so I can learn filters ground up in order to understand how software might be filtering inputs.

Thanks.

 

[Papabravo]

Filters are circuits that are designed to pass certain frequencies with little or no modification while other frequencies have their amplitudes greatly reduced. The "cutoff" or "corner" frequency marks the transition between the passband (where signals pass through unaltered), and the stopband where signals are stronly attenuated. In your case the output of the filter should be 3 dB down at 1 Hz as compared to a signal at say 0.1 Hz. If you measure the output at 10 Hz. you will have some idea how activly the filter is knocking down higher frequency signals.

Was that enough of an explanation or do you need more?

 

[naseeam]

Is 3dB always the cutoff frequency?

 

[Speakerguy]

If not otherwise specified, yes.

 

[Papabravo]

Is 3dB always the cutoff frequency?

Yes the term "corner frequency" comes from the piecewise linear approximation to a filter response. One linear segment approximates the passbend response and one linear segment approximates the rolloff. The "corner" where these two straight lines intersect is the "corner frequency" It just so happens that at the corner frequency the actual response of a first order system is -- are you ready for ths? -- 3 dB down.