Last modified by Iris Spruit on 2024/03/15 15:08


An electrocardiogram (ECG) measures the electrical activity of the heart muscle by using electrodes placed on the skin. These electrodes detect the electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle (heartbeat). ECG is measured in millivolt (mV) and the signal usually ranges between 1 and 5 mV. 

Availability, support and advice

For availability of ECG equipment within your unit, contact your lab coordinator. ECG equipment from BIOPAC or VU-AMS can also be borrowed from SOLO through the Helpdesk or by contacting


Below, a general protocol of measuring ECG with a two-lead configuration common at the FSW is described. Note that an adequate training is required before working with physiological data acquisition equipment and collecting such data from participants. If you are uncertain about the procedure, please contact your supervisor or lab coordinator



ECG can be measured with the BIOPAC ECG100C (wired) or RSPEC-R (wireless) modules, or with VU-AMS equipment.

Leads and electrodes

The ECG100C is typically used with one red lead 100S connected to VIN+ (and shield), one white lead 110S connected to VIN- (and shield) and one black lead 110 connect to GND. Note that the ground is not required when the participant is already connected to a ground on another BIOPAC wired module (see Grounding guidelines | BIOPAC). Optionally, the leads can be extended with an MEC110C. Usually, ECG is measured using disposable Ag/AgCl ECG electrodes (see Lab Supplies).

With the RSPEC-R you can measure both respiration and ECG. The RSPEC-R transmitter can be attached to a BioNomadix velcro strap with size 137 cm (BN-STRAP-137), which can be tied around the waist of the participant. Use the 45/50cm x 3 leads for BioNomadix (BN-EL45-LEAD3) to measure ECG. Usually, ECG is measured with disposable Ag/AgCl ECG electrodes (see Lab Supplies).

The VU-AMS comes with its own electrode lead bundles, either one to measure only ECG, or one with which you can measure both ICG and ECG. The black, white and green leads are used to measure ECG. Usually, ECG is measured with disposable Ag/AgCl ECG electrodes (see Lab Supplies).


For SSH researchers, supplies can be picked up at SOLO 1B11 in PdlC or 2.5.01 in Sylvius, see lab supplies for more info.

  • ECG equipment (see Setup)
  • 3 disposable Ag/AgCl ECG electrodes
  • Scrub gel (NuPrep)
  • Non-woven swabs
  • Gloves
  • Incidin OxyWipe

​​​​​​Skin preparation

Always wear disposable gloves (see gloves protocol) when you clean the participant’s skin and apply the electrodes. After use, remove the gloves and dispose of them.

Before applying the electrodes it is important to reduce the impedance (resistance) of the skin by removing oils and dead skin cells. It is recommended to use a scrub gel (NuPrep) for this. Do not use alcohol wipes as they are generally too aggressive for the skin.

  • Put on disposable gloves.
  • Put a little NuPrep scrub gel on a non-woven swab.
  • Rub the gel gently onto the skin.
  • When the skin remains wet, dry the skin with a clean swab or tissue.
  • Apply the electrodes directly after cleaning the skin.

Electrode placement

Place the electrodes 5 to 10 minutes before you start taking measurements, so as to allow the gel to work.

The number of electrodes and their placement can differ depending on the type of study. A common method is to use three electrodes for a two lead configuration (unless you are using multiple wired BIOPAC modules with a ground, in which case the ground electrode can be omitted, see BIOPAC grounding guidelines):

  • Place one electrode under the right collarbone (negative, V-)
  • Place one electrode on the left on the lower ribs (positive, V+)
  • Place one on the right just below the ribs (ground).

When drawing an imaginary line between the positive and negative electrode, the heart should be located in the middle. The location of the ground electrode is not crucial, but it is important that the it is not placed between the other two electrodes (see also Optimal ground placement | BIOPAC).

Which leads should be attached to these electrodes depends on the system that you are working with.


  • Attach the white lead to the electrode on the right, below the collarbone.
  • Attach the red lead to the electrode to the electrode on the left, on the ribs.
  • Attach the black lead to the grounding electrode on the right, below the ribs. 

When using the wireless RSPEC-R module, you can fix the strap with the transmitter around the participant’s waist and then attach the leads to the electrodes. Ensure the strap is placed between the  transmitter and the skin, so that the transmitter does not come into contact with the skin.


  • Attach the white lead to the electrode on the right, below the collarbone.
  • Attach the black lead to the electrode to the electrode on the left, on the ribs.
  • Attach the green lead to the grounding electrode on the right, below the ribs. 

BIOPAC electrode placement


VU-AMS electrode placement

Important when using BIOPAC leads: when attaching or disconnecting the leads, you must squeeze the plastic lock connector at the end of the lead. Never pull on the lead itself. This material is very fragile and breaks easily. Similarly, when using wireless modules and the leads need to be attached to or detached from the receiver unit, you should use the plastic squeezable connector and refrain from pulling on the leads. Do not knot or twist the leads, as it may damage them.

Cleaning up

  • Put on disposable gloves.
  • Remove the leads and, if present, the strap with the RSPEC-R transmitter.
  • The participant can then remove the electrodes him/herself. Removing the electrodes can be painful for some people. Depending on the sensitivity of the participant’s skin, there may be red marks visible. These will normally fade within a few hours.
  • The electrodes can be discarded in the bin.
  • If necessary, the leads can be cleaned carefully with Incidin OxyWipe.
  • When a strap has been used for the wireless RSPEC-R transmitter, the strap can be washed if necessary (use multiple straps to allow for drying), please contact when straps need to be washed.

Tips & Tricks

  • The participant must move as little as possible to prevent artefacts in the data.
  • The participant must be comfortable and sit in a natural posture with both feet on the floor.
  • Check the ECG signal before starting actual data collection. The figure below shows a typical ECG signal (recorded with BIOPAC AcqKnowledge).
  • When the data looks irregular or shows a flat line, check whether the leads are properly attached and whether the electrodes are still properly attached.
  • If the data looks upside down (i.e., when the R peaks are pointing down) it is likely that the V+ and V- leads have been swapped around. Check whether the V- lead is attached to the electrode under the collarbone and the V+ lead to the electrode on the left-hand side below the bottom rib.
Typical ECG signal

Typical ECG and HR data

More information

  • BIOPAC webinars:
  • Papers:
    • Measuring ECG in an MRI scanner: Niendorf, T., Winter, L., and Frauenrath, T. (2012). Electrocardiogram in an MRI Environment: Clinical Needs, Practical Considerations, Safety Implications, Technical Solutions and Future Directions, in: Millis, R.M., Ed., Advances in Electrocardiograms – Methods and Analysis, chapter 17, pp. 309-324.
    • Nederend, I., ten Harkel, A. D. J., Blom, N. A., Berntson, G. G., & de Geus, E. J. D. (2017). Impedance cardiography in healthy children and children with congenital heart disease: Improving stroke volume assessment. International Journal of Psychophysiology, 120, 136-147
Tags: Physiology
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