Circuit diagram of wireless ECG monitoring system based on GPRS

This is a new electrocardiograph system based on GPRS standard. The system consists of three parts: a monitoring terminal (portable ECG monitor), a wireless network and a monitoring center station. Among them, the wireless network uses modern communication networks and computer networks to provide access devices at the monitoring terminals; the monitoring center is generally built in the hospital's monitoring center, and ECG monitoring is a part of the center; the monitoring terminal realizes wireless real-time monitoring The essential.

ECG monitoring terminal hardware

The entire ECG monitoring terminal circuit mainly includes: ① ECG signal acquisition and processing circuit, which includes a preamplifier circuit, filter circuit and rear amplifier circuit; ② ECG monitoring circuit, QRS wave extraction detection circuit, MCU and LCD display ;③Remote communication part, including MCU, GSM/GPRS module, SIM card and radio frequency circuit;④Power circuit. The ECG signal is divided into two paths after coming out of the back-pole amplification circuit. One path enters the band-pass filtering and detection circuit into the MCU to realize the judgment of abnormal heart rhythm and premature beats; the other path MCU enters the memory and is stored as a complete ECG signal.

preamplifier stage

The ECG preamplifier requires very high input impedance and common-mode rejection ratio, low zero drift, low offset, low power consumption, especially low 1/f noise voltage. Generally, a in-phase parallel differential three-op amplifier instrumentation amplifier is used In order to obtain good comprehensive performance, this design uses the low-cost instrumentation amplifier AD620 from Analog Device Company in the United States, and obtains good circuit effects. The circuit is shown below. The gain of the preamplifier stage of this design is set to amplify 7 times. Combined with subsequent amplifiers, it forms a channel gain of 300 times.