BIOPAC® Systems, Inc. Logo

Grounding guidelines

When a single subject is connected via wires to a single MP system, there should generally be one and only one ground connection to that subject*. When multiple subject grounds are used, ground loops can occur: current will flow between the different grounds. This will result in distorted data.

When recording with the EDA100C (GSR100C), EBI100C, or the NICO100C, a ground is already provided through the VIn- or I IN connection (in these three cases as well as their -MRI brethren, an internal connection makes VIn- for EDA amplifiers or I IN for the bioimpedance amplifiers electrically identical to ground). Consequently, no other ground connection to the subject* need be used. In some cases, particularly when power line noise is apparent despite the presence of a single ground, it is beneficial to have more than one ground.  In the case of the EDA100C (or GSR100C), additional connections can be made through AC-coupled lead adapters (CBL205).

If using BioNomadix wireless transmitters, the subject requires one ground per transmitter. This only applies to units making an electrical connection with the subject. In addition, the BN-PPGED does not require an extra ground, as the VIN- of the EDA already acts as a ground. However, BN-ECG2, BN-EMG2, BN-EEG2, BN-EOG2 and BN-EGG2 all require separate ground connections.

* “To the subject” meaning specifically an electrical connection to the subject.  Many other BIOPAC components, such as the respiratory effort transducer and photoplethysmogram transducer have ground connections to the equipment but are not relevant to this topic because these devices do not make electrical connections to the subject and thus will not produce ground loops through the subject.

To record EDA (GSR) simultaneously with other biopotential signals (for instance, ECG, EEG, EOG, EGG, EMG, or ERS):

1. Connect the Vin- lead of the EDA as ground (when using disposable electrodes there will be nothing connected to the “GND” connection on the front of the GSR100C).

2. Connect an AC-coupled ground to the ECG100C (e.g., LEAD110A connected through CBL205 to the ECG100C’s “GND” connection).

The AC coupled lead will not influence the EDA measurement when all electrodes are connected, but it will continue to function as a ground for the ECG amplifier if the electrode connected to VIn- on the GSR100C is disconnected from the subject.

For more on this topic see “Special Cases” under “Multiple amplifiers per subject or multiple subjects per system.”

Note—If using any two of the following on the same subject connected directly to the same MP system at the same time: EDA100C (GSR100C), EBI100C, or NICO100C, ground loops will be a problem; you will not be able to make absolute measurements (such as SCL). BIOPAC recommends the use of BioNomadix modules in this case as these transmitters do not share a common ground. Alternatively, one or more of the measures may be made through an additional MP system or with an IPS100C/HLT100C/OUTISO to optically isolate the ground connections.  More information may be found under Galvanic Isolation Guidelines.

Associated Applications

Spotlight On
Buy MP41 with BSL

Practical Lab Kit with BSL 4 & MP41

BSL Home enables students to safely conduct hands-on physiology labs wherever they are! Purchase this complete lab solution to preserve practical lab experience! Includes MP41 Unit+Lead Set with BSL Home software, EL503 electrodes, WRAP1 self-adhering wrap for EEG lessons, and disposable 9 V battery. For instructors—BSL Home makes it easy for instructors to continue running practical […]

View All
Latest News

New Citations | Logic Games and Meditation: the Key to Unlocking our Brains?

Studying Cognitive Activity with fNIR! The age-old game of chess is known as a thinking man’s game, where foresight, critical thinking, and strategy are required to become a good chess player, and the terms “genius” or “brilliance” are bestowed upon the chess masters of the world. As such, chess is an excellent cognitive tool to […]

Electrocardiography Guide Now Available

BIOPAC’s comprehensive Introductory ECG Guide addresses fundamental to advanced concerns to optimize electrocardiography data recording and analysis. Topics include: ECG Complex; Electrical and Mechanical Sequence of a Heartbeat; Systole and Diastole; Configurations for Lead I, Lead II, Lead III, 6-lead ECG, 12-lead ECG, precordial leads; Ventricular Late Potentials (VLPs); ECG Measurement Tools; Automated Analysis Routines for extracting, […]

Read All
Request a Demonstration
Request a Demonstration