Sensor FAQ
Below are some frequently asked questions about our sensors. If you have any additional questions don’t hesitate to contact us.
Why is silver chloride used on sensors? Why not just use silver?
Answer:
The chloride ion is required in a silver-based biopotential electrode. Some sensors undergo a process which converts a small portion of the silver coating to silver chloride. Chloride is also present in the electrode gel. A silver/silver chloride electrode converts ionic energy into electric current and works as a transducer through an oxidation/reduction reaction at the electrolyte interface. This half-cell reaction is characterized by fast electrode kinetics, meaning that a sufficiently high current can be passed through the electrode with high efficiency of the redox reaction. The redox reaction is the dissolution of the silver metal or a cathode deposition of the silver ions from the electrolyte. A silver/silver chloride electrode is best because it provides a very high signal-to-noise ratio and it allows the sensor to “recover” after a defibrillation discharge. This quick recovery is required for the ECG trace to be displayed within two seconds so that the effectiveness of the defibrillation can be assessed.
What determines whether or not a sensor or electrode is radio-translucent?
Answer:
Radio-translucenst is defined as allowing X-rays to penetrate the sensor or electrode. Radio-translucent is dependent on the amount of metal present; typically a radio-translucent sensor / electrode construction is composed of a molded, carbon filled stud (replacing stainless steel or nickel plated brass) and a silver / silver chloride coated sensor (with as little silver as the application can support).
Why aren’t all sensors “One Piece” if it will reduce cost?
Answer:
“One piece” sensors do not allow for the same “clamping” into the electrode matrix that can be achieved in an eyelet / snap design. Using a “one piece” sensor requires innovative product design and assembly techniques to assure that the sensor will remain in place during product use.
What size sensor should I use?
Answer:
The choice of a sensor is driven by performance requirements and cost. The larger the flange of the silver / silver chloride eyelet the more surface area is available for conduction, the risk of “pull through” is reduced and the amount of silver used is increased.
How much silver/silver chloride is needed for the sensors I will use in my electrode?
Answer:
The amount of silver / silver chloride required is dependent on the application – monitoring or active. For most monitoring applications, a silver thickness 0.075mil on a glass filled plastic molded eyelet will provide satisfactory performance to the AAMI EC12 requirements. It is recommended that the user validate the performance of the sensor in its final design configuration through stability and validation testing.
