Electrocardiogram (ECG) 12-lead is a non-invasive method used to monitor the electrical activity of the heart. Errors in heart recording lead to misdiagnoses in patients. One effort to improve the quality of ECG recording is by determining the data length recording time. This study aims to find the best sampling rate used by the STM32F7 in recording 12-lead ECG signals through precordial and limb lead placement. The research methodology involves configuring the ADS1293 module to record ECG signals from electrodes at precordial lead placement. ECG signals are recorded at varying sampling rates, namely at 200Hz to 1000Hz. After being transmitted, the ECG signal is analyzed using the signal-noise ratio (SNR) method to determine the ratio of noise and the original signal. The analysis results show that the higher sampling rate on the STM32F7 can provide better ECG signal details and increase accuracy in detecting QRS complex and ST segment changes. However, it is important to remember that using higher sampling rates also requires more resources and affects data processing speed. The best sampling rate obtained was 400 Hz with a delay setting of 2s, resulting in an SNR value of 12.8386 dB. This research provides a better understanding of the effect of sampling rate on the ADS1293 module with processing using the STM32F7 in recording 12-lead ECG signals through precordial and limb lead placement. This information may aid the development of medical devices that utilize the STM32F7 to incorporate cardiovascular health, taking into account the trade-off between recording quality and resource usage.