Frequency Adaptive Line Voltage Filters

A method implemented on an electronic computing device for reducing noise from an electrical signal, the method comprising:

• obtaining a first sampling rate for the electrical signal, the first sampling rate being a rate at which voltage readings are obtained for the electrical signal, each voltage reading comprising a data component and a noise component;
• determining a first time interval from the first sampling rate, the first time interval being equal to a reciprocal of the first sampling rate;
• determining a first sampling time and a second sampling time, the first sampling time occurring at any random point in the electrical signal, the second sampling time being equal to a sum of the first sampling time and the first time interval;
• determining a first number of noise samples to be obtained within one frame of the electrical signal, the one frame of the electrical signal comprising either one period of the electrical signal or three periods of the electrical signal;
• obtaining a first voltage reading sample at the first sampling time;
• obtaining a second voltage reading sample at the second sampling time;
• determining a second sampling rate for the electrical signal, the second sampling rate being a rate at which simulated noise sample readings are obtained during the one frame of the electrical signal;
• determining a second time interval from the second sampling rate, the second time interval being a reciprocal of the second sampling rate;
• determining whether there is a first simulated sampling time between the first sampling time and the second sampling time;
• and
• when it is determined that there is a first simulated sampling time between the first sampling time and the second sampling time:
• obtaining a third voltage reading at the first simulated sampling time by interpolating the first voltage reading sample and the second voltage reading sample;
• applying the third voltage reading to a low-pass filter;
• obtaining from the low-pass filter a first noise value at the first simulated sampling time;
• storing the first noise value in memory;
• obtaining from the low-pass filter a second noise value at a second simulated sampling time, the second simulated sampling time being equal to a sum of the first simulated sampling time and the second time interval, the second simulated sampling time occurring later than the second sampling time;
• storing the second noise value in memory;
• obtaining a third noise value at the second sampling time by interpolating the first noise value and the second noise value;
• and
• subtracting the third noise value from the second voltage reading at the second sampling time.

A method implemented on an electronic computing device for reducing noise from an electrical signal, the method comprising:

• determining a number of noise samples;
• determining a first sampling rate for the electrical signal;
• determining a first time interval for the electrical signal, the first time interval being equal to a reciprocal of the first sampling rate;
• determining a second sampling rate for the electrical signal, the second sampling rate being equal to the first sampling rate multiplied by a scaling factor greater than 1;
• determining a second time interval for the electrical signal, the second time interval being equal to a reciprocal of the second sampling rate;
• using the second time interval to determine index array locations in a computer memory array, there being one index array location for each second time interval time period within one frame of the electrical signal;
• obtaining a voltage reading at the first sampling rate;
• determining a first sampling time corresponding to the voltage reading;
• determining a second sampling time within a frame that is closest in time to the first sampling time;
• determining an array index location corresponding to the second sampling time;
• applying the voltage reading to a low pass filter at the array index location corresponding to the second sampling time;
• determining a noise value for the voltage reading from the low pass filter;
• subtracting the noise value from the voltage reading.

A method implemented on an electronic computing device for reducing noise from an electrical signal, the method comprising:

• obtaining a sampling rate for the electrical signal, the sampling rate being a rate at which voltage readings are obtained for the electrical signal, each voltage reading comprising a data component and a noise component;
• determining a time interval from the sampling rate, the time interval being equal to a reciprocal of the sampling rate;
• determining a number of voltage readings to be obtained within a first frame of the electrical signal, the first frame being any random frame in the electrical signal, the first frame of the electrical signal comprising an integer number of periods of the noise component of the electrical signal for which there are equally spaced voltage readings corresponding to the time interval, each voltage reading being obtained one time interval of time after a previous voltage reading is obtained;
• at each time interval within the first frame:
• obtaining a voltage reading;
• applying the obtained voltage reading to a low-pass filter;
• obtaining from the low-pass filter a noise value;
• and
• subtracting the noise value from the voltage reading.