Electronic circuitry contains new operational amplifier which incorporates monolithic super-gain transistors. Electrode does not provide voltage amplification; instead, it acts as current amplifier to make it possible to pick up electrical potentials from surface of highly resistant dry skin

Cleveland, G. J.

Luce, R. S.

English

NASA Technical Reports Server

May 1973	 B73-10146 
NASA TECH BRIEF
•h" ,'1 
Lyndon B. Johnson Space Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
A New Dry Biomedical Electrode 
Cover Over	 160K Resistor	 Conductive 
Hybrid	 External To Hybrid	 Metal 
Circuit	 Circuit	 Trace	 Cable To 
ECG Amplifier 
/	 f	 __ .	 NCable 
/	 I	 Silver-Silver	 Attachment 
Epoxy	 Ceramic Hybrid	 I	 Chloride	 Points 
Resin	 Substrate	 Conductive	 Electrode 
Sealant	 In Disk Form	 Epoxy Adhesive	 Material 
Figure 1. Dry Electrode 
The problem: 
When electronically monitoring heart beats and other 
life signs by means of electrodes attached to the skin, 
it is normally necessary to use some method to over-
come the resistance of the skin to current. For this 
purpose, a moist conductive paste is used to attach the 
electrode. Over a period, this paste may irritate the skin, 
requiring periodic removal of the electrode.
The solution: 
A dry, strap-on electrode that will not irritate the 
skin houses an improved electronic amplifier and cir-
cuitry that matches the impedance of the skin. 
How it's done: 
Figure 1 is a schematic of the electrode which uses 
the silver-silver chloride system common in electrodes. 
Ag/Ag Cl
.':. 160K2 Very Low 
-I.'. Input Bias 
Op-Amp 
+
30 pf
i0002
Comm. 
Shield
To ECG 
Amplifier 
+V 
—V 
0.01 /if 
Figure 2. Buffer Electronics for dry Electrode 
- --------_______ 
W	 (continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19730000146 2020-03-17T07:07:50+00:00Z
However, the e1ectroniccircuitiy (Figure 2) contains a 
new operational amplifier that incorporates monolithic 
super-gain transistors. It has an extremely low input 
bias current that makes possible an exceptionally high 
input impedance. This allows the electrode to be used 
without conductive paste. 
The electrode does not provide voltage amplification 
as would be the case with conventional amplifiers. 
Instead, it acts as a current amplifier to make it possible 
to pick up electrical potentials from the surface of 
highly resistant dry skin. The amplifier is configured as 
a voltage follower, and is provided with decoupling 
capacitors on the power supply leads. The circuit in-
cludes two 160 kilohm resistors in the input lead to 
protect the patient in the event of failure within the 
assembly or the power supply. 
The dry electrode can be attached to the skin with 
no surface preparation, has no offset, no temperature 
instability, and requires no auxiliary current sources 
in the signal amplifier. It is the same size as a wet 
electrode and may be used in its place without modifi-
cation to signal amplifiers.
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Lyndon B. Johnson Space Center 
Code JM7 
Houston, Texas 77058 
Reference: TSP73.10146 
Patent status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
Patent Counsel 
Lyndon B. Johnson Space Center 
Code AM 
Houston, Texas 77058
Source: R. S. Luce and

G. J. Cleveland of
Lockheed Missiles & Space Co.

under contract to

Johnson Space Center
(MSC-14321) 
B73-10146	 Category 02, 05


A new dry biomedical electrode

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