Materials and Methods
In this study, for development, some prerequisites were important to be determined before development of device. signal receiving method then removing artifacts from signals considered firstly. Then determining the most important factors in evaluation, and detecting way of abnormal contractions. Details of development are described below.
For continuously monitoring, dry contact electrodes are used by people (15). In this research, we used dry contact electrodes. In order to receive uterine contraction signals and remove noises of EHG signals, we combine amplifiers and filters.
Amplifier
We needed an Amplifier that could convert an EHG signal that has an amplitude of mv into output with a voltage range of several volts. Because it should be able to receive and convert to a digital signal. So, several layers of amplifiers are needed. Amplification layers with required filters are developed to get the maximum signal-to-noise ratio (SNR) at output. It is considered as an important factor because higher SNR value lead to resolution. SNR is defined as 20 log10(s/σ ). The maximum amplitude in the averaged time period signal is s (16).