Vector ECG
This page shows how to set up a vector ECG by connecting USB DUX to a standard ECG. In addition also the carotis pulse can be measured.
If you want to build your own ECG preamp you can use this circuit.
Connecting the ECG to USB DUX
| ECG | USB DUX: pin |
| I | 8 (Ch.1) |
| II | 7 (Ch.2) |
| III | 6 (Ch.3) |
| GND | 16-21 |
The ECG is an old analogue one. Only the amplifier in the ECG is used.
| Pressure transd. | USB DUX: pin |
| signal | 5 (Ch.4) |
| +5V | 14 |
| -5V | 15 |
| GND | 16-21 |
The pressure sensor is a standard pressure sensor for blood pressure measurements. To measure the carotis pulse its AC component has to be amplified by factor 100. This is simply done by a standard OP (TL071). Both the pressure sensor and the amplifier get the supply from the USB DUX board. Thus, all measurement devices (ECG and pressure sensor) are electrically isolated from the computer (good for the quality of the results, good for the patient).
Software
This software plots Einthoven I and aVF and constructs a vector ECG in realtime. The ECG and the vector ECG can be stopped any time. The frozen plots can be measured and printed.
The program has been tested on SuSE 9.0 personal edition with QT-devel installed. Please note that gnuplot is needed to print the ECGs/vector loops.
Download: Version 1.12 of the vector plot: compressed tar.
Known bugs:
- International characters are not printed properly.
Feedback:
Bernd Porr and my homepage is here.