## Removing 60Hz from ECG using digital band stop filter

Let’s make a filter, which filters off the 60Hz frequency from the ECG signal. As we know, the American power supply is 60Hz. This is a common noise in biomedical signals while the industrial power supply powers them. This type of noise can be defined easily and can be filtered as parameters of noise are known.Here is one example of how to implement an FIR filter using mathematical tools, like Matlab. This can be done using a microcontroller, like ARM or even AVR, because the frequencies are up to 1 kHz.Initial conditions: f0=60Hz – power supply frequency;fs=500Hz – sampling rate;frequencies who define complex zeros: we get w0=0.754;Positions of complex zeros: Zeros and poles in z plane System Function From it we can calculate filter coefficients: And filter coefficients: b3 = 1; b2 = -2cos(w0); b1 = 1 Also we know that: And here we get filter characteristics: We have a band stop filter at 60Hz, and its jam at 60Hz is -300dB. Bellow is a filter structure: Now using this filter we can filter ECG signal: As you can see, this is a simple FIR filter. In other words, there is nothing more than an average function that doesn’t need…

## Skin reflectance spectra

According to earlier skin reflectance modeling, skin reflectance spectra were calculated for skin with the most common properties: Melanin (volume fraction 2% in Epidermis); hemoglobin HbO2 and Hb (150 g Hb/liter ) and Thickness of collagen tissue in papillary dermis about 0.1mm.

## Skin spectral properties

Understanding how light interacts with skin can assist in designing physics-based dermatological image processing. The key is to understand how light interacts with skin tissue. The skin consists of different layers with different spectral properties. When the incident light is applied to the skin layer, it is absorbed, and another part is scattered. The main layers of skin are as follows: Stratum cornea practically doesn’t absorb light but diffuses it; Epidermis consists of cells producing the pigment melanin. Melanin strongly absorbs light wavelengths towards the ultraviolet part; Dermis is next to the skin layer, consisting of collagen fibers. It can be split into two sublayers: The papillary dermis and the dermis itself. The papillary dermis consists of a high density of collagen fibbers who are strong scatterers of light. The primary requirement for the model is that light has to be scattered. Stratum cornea is supposed a scattering filter. Skin can be characterized as follows:

## Histological Skin Structure Diagram

Skin is a brilliant structure of our body. It is very elastic and pretty strong to protect internal tissue. It also acts as a thermoregulator of our entire body protecting us from overheats when we sweat and when there is cold, the blood flow is reduced to skin tissues to save heat to the body’s inner organs. Skin is pretty resistant to harmful chemicals, microorganisms, and if dry, it has high electrical receptivity. From the biochemical side, the skin can produce vitamin D when exposed to sunlight, which is essential for our bones’ growth and maintenance. The extensive network of nerves within the skin feeds information continuously to the brain concerning our surroundings. So it is full of sensors to know the external world like temperature, pressure. Don’t even let me start about skin importance in the fashion industry. About how much there is the attention paid to cosmetics, beauty shine. Skin can show you if you’re shy or cold, or afraid. As you see, your body’s top layer of skin can tell you so many things; get to know it. Skin structure diagram Mainly people used to name only two layers of skin epidermis and dermis. But in reality,…