Coping with ECG equipment signal acquisition of design challenges

Electrocardiogram of interference signals from the power supply of 50/60Hz interference, patient activities result in movement artifact, electro-surgical equipment, defibrillator pacemaker pulse, pulse and other monitoring equipment caused by RF interference.

How to deal with the signal acquisition process challenges? this article will tell you the address. Signal acquisition challenges large DC offset and the emergence of various interference signal causes the ECG signal measurement challenges. Typical electrode voltage up to 300mV. Interference signals from the power supply of 50/60Hz interference, patient activities result in movement artifact, electro-surgical equipment, defibrillator pacemaker pulse, pulse and other monitoring equipment caused by RF interference. ECG accuracy in the required will vary according to the terminal equipment changes depending on the needs: standard monitoring equipment 0.05 ~ 30Hz frequency diagnosis devices require 0.05 ~ 1000Hz frequency can be eliminated by two input AC line noise, high-input impedance instrumentation amplifier (INA) offset some 50Hz/60Hz common mode interference. To further eliminate line power supply noise, signal with amplifier by right leg was reversed and the patient refoulement. Just a little micro-current even less to achieve significant improvement in the CMR and remain in the UL544 limit. In addition also uses 50/60Hz digital notch filter further reduce interference.

Analog front end options to optimize power and analog front end for PCB area for the purposes of a portable ECG is critical.

Technical improvements, the current offers a variety of front-end options: 1. use a low resolution ADC (requires all filter) 2. using high resolution ADC (requires less filter) 3. use of Σ-Δ ADC (without filter, in addition to the INA, amplifier, DC offset) 4. use the sequence and synchronous sampling method. Use a low resolution (16-bit) ADC, the signal needs to be significantly gain (increases usually 100-200 times) to achieve the necessary spatial resolution. High resolution (24-bit) Σ-Δ ADC, signal need for 4 to 5 times more modest gains. Therefore you can remove eliminate DC offset the required second gain stage and circuit. This will be achieved in the area and the overall cost. Σ-Δ method also retains the contents of the entire frequency signal and data post-processing provided sufficient flexibility. With the order method, create a single-channel ECG leads can be multiplexed into a single ADC. In this way, adjacent channels are inevitably exist. With synchronous sampling method can be used for each special ADC channels, channel does not exist between the offset mentioned previously.