Produkt-Neuheit

Why lead-free technology?

Figaro introduced the well-known KE Series oxygen sensors 40 years ago, developing a range of galvanic sensors tailored to different application needs. These sensors were designed to offer varied operational lifespans, response times, and flexible fitting options to integrate seamlessly into OEM enclosures. These sensors along with many other electrochemical oxygen sensors not defined as being lead-free, contain a lead anode which gradually depletes over time.

Lead, amongst other substances, has been found to be harmful to human health and the environment, Steps have been taken to restrict its general usage. In the electrical and electronics industry, the RoHS (Restriction of Hazardous Substances) Directive came into effect in 2006 restricting the use of hazardous materials, including lead (Pb), in electrical and electronic equipment sold within the EU but electrochemical oxygen sensors were exempt due to the lack of viable alternatives at the time. This sparked the creation of the innovative lead-free KE-LF series, which has been offered to the market alongside the classic KE series for the past three years.

Now that lead-free sensor technology has advanced, the RoHS exemptions have been phased out or are under review. Manufacturers should now be transitioning to RoHS-compliant, lead-free alternatives to meet regulatory requirements while maintaining sensor performance. Maxell and Figaro have stopped production and sales of the original lead-containing KE series to concentrate solely on the lead-free sensors.

What are oxygen sensors used for?

Oxygen sensors are used in a diverse range of applications including, but not limited to:

Modified atmosphere packaging for food
Industrial combustion processes
Biotechnology for optimal growth of cell cultures and bacteria
Waste water biological treatment – optimisation of aeration process
Fuel Cell Technology for maximum efficiency.
Additive manufacturing processes ( 3D Printing)
Personal Safety - monitoring oxygen levels in confined spaces e.g. aircraft cabin, a mine or tunnel
Environmental monitoring
Medical Devices e.g. incubators. The sensor can also be used in ventilators and anaesthesia
equipment but is not itself CE or UKCA certified.

What models of Oxygen sensor do Figaro supply and what are their differences?

Figaro offers two sensor types: Galvanic, and Potentiostatic electrolytic.

The major selling feature of the galvanic sensor is that it requires no external power, it generates its own power through its electrochemical reaction. Potentiostatic sensors require a constant external voltage and are typically mounted on the PCB. Due to lack of circuitry and power requirements, the galvanic sensor is simpler to maintain and has no associated running costs.
Galvanic sensors are not as sensitive to external factors such as temperature and humidity so are more durable and reliable in applications subject to changes in the environment.
Potentiostatic electrolytic sensors are more sensitive to small changes in oxygen concentration and are more accurate, particularly at low oxygen concentrations, because they operate under a constant applied voltage, maintaining stable electrochemical reactions. These sensor have a smaller footprint and a quicker response time compared to galvanic sensors.

For more information on the two sensor types and mode of operation please read on....


Lead-free, potentiostatic, electrolytic type oxygen sensor TGS4260

The TGS4260 is a three electrode electrochemical cell, comprising a working electrode (WE), a counter electrode (CE) and a reference electrode (RE). All three electrodes are contained within a resin housing and immersed in a liquid electrolyte.

A constant voltage (potentiostatic control) is applied between the working (WE) and reference electrodes(RE) to drive the oxygen reaction and the electrolytic current generated between WE and CE is meanwhile measured.

When the TGS4260 sensor is placed in the presence of oxygen, maintaining the potential of the WE at a predetermined
negative value with respect to the RE potential causes oxygen to be reduced at the WE and water to simultaneously oxidise at the CE. During these electrochemical reactions, ionic conduction occurs in the electrolyte and electronic conduction
occurs in the external circuit. The generated electrolytic current is converted to a voltage output which is proportional to oxygen concentration.


The formula for the reaction of the working electrode is: O2 + 4H+ + 4e- -> 2H2O
The formula for the reaction of the counter electrode is: 2H2O - > O2 + 4H+ + 4e-






Lead-free, electrochemical oxygen sensor family KE-LF

The KE-LF series oxygen sensors; KE-25LF, KE-25F3LF, KE-25F3LFM, KE-12F3LF and KE-50LF are unique galvanic cell oxygen sensors developed by Maxell, Ltd. in Japan.

The KE-LF series succeeds the well- established KE series, providing a lead-free alternative. As pioneers in galvanic lead-free oxygen sensor technology, Maxell has applied its experience to develop sensors that maintain the exceptional performance of their lead-containing predecessors. These sensors maintain key features such as no cross-sensitivity to CO2, good chemical resistance, and long operational life. Designed to meet the growing demand for oxygen monitoring, the KE-LF series delivers reliable and precise performance across a wide variety of applications.
The KE-LF series sensor functions as a metal-air battery, consisting of a metal anode, an oxygen cathode, and a weakly acidic electrolyte. Oxygen molecules pass through a permeable membrane into the electrochemical cell, where they are reduced at the cathode in the presence of the electrolyte. The resulting current between the electrodes is directly proportional to the oxygen concentration in the measured gas mixture.
The sensor's output voltage, measured across a thermistor (for temperature compensation) and a resistor, serves as the signal, with changes in voltage reflecting variations in oxygen concentration.

A small internal air bubble helps compensate for pressure fluctuations, ensuring stability. The sensor housing is made of durable ABS resin.

For more Technical information please see below or contact Figaro.

https://www.figaro.co.jp/en/product/docs/ke-lf_product%20information%28en%29_rev08.pdf



FIGARO Engineering Inc.
1-11-46 Senbahigashi, Mino, Osaka 562-0035, JAPAN
Phone: +81-72-728-2560
E-Mail: figaro@figaro.co.jp

Figaro Europe Office
Phone: +81-72-728-2560 (Germany)
Phone: +44-7483-411193 (UK)