2026-10-03
Portable single-channel electrocardiograph
Operating instructions
This portable single-channel cardiograph is designed to monitor the heart's electrical activity. The cardiogram is displayed on the built-in screen and can be transmitted via Wi-Fi to a web browser on a computer, smartphone, or tablet. No internet access or app installation is required for operation.
Important! Electrodes should only be attached to the body and measurements taken when the device is powered by its battery and the USB cable is disconnected. Remove all electrodes before charging, updating the firmware, or connecting the USB cable. The STOP mode does not disconnect the electrodes from the circuitry and does not waive this requirement.
Preparing for Measurement
Check the device casing, cable, and electrodes for damage. Do not use the device if the insulation or connectors are damaged; the fault must be repaired first. If the battery is low, charge it first with the electrodes removed, then disconnect the USB cable.
Sit in a comfortable position. Keep the device and the measurement site at least one meter away from active household electrical appliances, especially computers and monitors. Rest your forearms on a stable surface; your arms should be relaxed, and the electrode cable should not be under tension. The skin at the contact points must be clean and free of creams or dirt. If necessary, clean the skin with a wipe lightly moistened with water or alcohol. Do not use wipes containing creams or oily additives.
Turning on the Device and Connecting Electrodes
- Ensure the USB cable is disconnected. Turn on the power using the device's power switch. Status indicators and the ECG graph area will appear on the display.
- Insert the electrode cable connector fully into the corresponding socket on the device, without using excessive force.
- Attach the red electrode to the right hand and the green one to the left. Position the clips across the palms as shown in Figure 2. The metal contact surfaces must be in firm contact with the skin.
- Attach the yellow electrode to a free finger or another convenient area of skin, such as the wrist, ensuring stable contact (Fig. 3). For the third contact, you can use a different type of electrode that ensures reliable electrical contact with the skin, such as this one. This electrode helps reduce interference.
- Relax your hands and remain still. Once reliable contact is established with the measuring electrodes, the "LO!" warning should change to "OK".
 Fig. 1 Red electrode on the right hand, green on the left |  Fig. 2 Placement of two electrodes on the palms |  Fig. 3 Third (yellow) electrode for noise reduction. Shown here attached to a finger |
Viewing the cardiogram on the display
After connecting the electrodes, wait for the signal to stabilize. This usually takes up to 10 seconds. During this time, baseline drift and irregular fluctuations may occur due to contact establishment and filter settling processes.
Do not talk, move your fingers, or squeeze the clips tightly during the measurement. Muscle tension and electrode movement create interference that may appear as extra waves on the graph.
A short press of the device button pauses the cardiogram update on the built-in display. Pressing it again resumes the display. "RUN" mode indicates the graph is moving; "STOP" indicates the selected segment has been paused for viewing. The battery charge level is displayed as a percentage; This is an estimated value that is updated using smoothing.
Viewing the ECG in a browser
- Turn on Wi-Fi on your computer, smartphone, or tablet.
- Find the MADRA-ECG-MONITOR network and connect to it. No password is required.
- If your device indicates that the network has no internet access, confirm that you want to keep the connection. An internet connection is not required to view the ECG.
- Open your browser and enter http://192.168.4.1 into the address bar. You must enter the address into the address bar itself, not into a search engine's search field. Automatic open...pages are not required.
- An ECG graph will appear on the device page. When the electrodes are connected and making good contact, you can view the cardiogram, the calculated heart rate, and the estimated QRS complex duration.
When connecting to the device's network, internet access via your previous Wi-Fi network may be lost. This is normal: the cardiograph creates its own local network. You can reconnect to your regular network after the measurement is complete.
To save a selected segment, first stop the graph using the STOP button on the web page, then remove the electrodes and take a screenshot using your computer or smartphone. It is recommended to save the graph along with the timeline and readings. Stopping the graph does not automatically save the data to a file; you must save the desired segment before closing or refreshing the page.
Finishing Use and Charging
- If you need a snapshot of the cardiogram, stop the graph and save the image.
- Remove all electrodes from your body and turn off the device.
- Clean the contact surfaces according to the electrode manufacturer's recommendations. Do not immerse the device or connectors in liquid.
- If necessary, connect power to the charging module's USB input. Do not attach electrodes to your body while charging.
Store the device in a dry place, avoiding overheating, impacts, and cable strain. If you notice unusual heating, an odor, or battery deformation, stop using and charging the device.
If the device is not working properly
- Display does not turn on. Check the power switch position and battery charge level. Disconnect the electrodes before connecting the charger.
- Wi-Fi network not visible. Ensure the device is turned on, wait a few seconds, and refresh the network list.
- Page does not open. Verify that you are connected specifically to the MADRA-ECG-MONITOR network and are accessing the address http://192.168.4.1. If your smartphone automatically switched to another network due to the lack of an internet connection, select the device's network again.
- "LO!" is displayed. Check the cable connector and ensure the red and green electrodes are making proper contact with the skin. Also, check the yellow electrode; poor contact here can increase interference even without triggering the "LO!" warning.
- Graph is not moving. Check if "STOP" mode is active. Resume the display on the screen you are currently using.
- Excessive interference or significant baseline drift. Relax your arms, adjust the electrodes, relieve any tension on the wires, and move away from operating electrical appliances. After adjusting the electrode contact, wait for the signal to stabilize.
- Pulse or QRS readings are unstable. First, ensure a stable ECG trace. Movement, muscle interference, and poor contact can lead to errors in automatic calculations.
The device records a single-lead ECG. Pulse and QRS duration readings are estimates, and the resulting ECG trace does not replace a clinical ECG or a physician's diagnosis. Do not use this device to self-diagnose or alter your medical treatment.