O2 oxygen sensor KE-LF

electrochemicalfor medical oxygen monitoringfor indoor air quality

Overview
Lead anodes in electrochemical oxygen sensors were previously listed as an exemption under the EU RoHS directive. A 2022 final report concluded that lead-free galvanic oxygen sensors are viable alternatives for many applications, including medical devices. Maxell developed the lead-free KE-LF series (released November 2019) using a purposely formulated weak-acid electrolyte. KE-LF models offer long service life, minimal CO2 influence and are positioned as environmentally friendly replacements for the leaded KE series.
As of March 2024, Maxell discontinued sales of its lead-containing KE series and promoted the transition to the KE-LF series.

Features

• Lead-free galvanic-cell type oxygen sensor
• Weak-acid electrolyte providing minimal sensitivity to CO2
• Long service life (approx. 3 to 10 years depending on model)
• Stable output voltage without external power
• Operates at room temperature with no warm-up time

Applications
Suitable for combustion gas monitoring, biotechnology equipment, food storage, education and medical devices.

• Environmental controls: combustion gas monitoring
• Health & safety: air conditioning and oxygen deficiency monitoring systems, oxygen concentration meters (oxygen monitors)
• Biotechnology: oxygen incubators, anaerobic bacteria cultivators, oxygen meters
• Medical devices: ventilators, anesthesia apparatus, oxygen concentrators, infant incubators, veterinary devices
• Food industry: plant factories, food storage units
• Health equipment: oxygen capsules

Basic structure / Measurement principle
The galvanic cell-type oxygen sensor comprises a cathode, an anode, an electrolyte and an oxygen-permeable membrane (similar to a metal–air battery). The membrane limits oxygen diffusion to the cathode; oxygen reduction at the cathode generates current between cathode and anode. A built-in compensation resistor converts this current to a voltage proportional to oxygen partial pressure, enabling oxygen concentration measurement via sensor voltage.

Specifications (summary)
Model: KE-25LF / KE-25F3LF | KE-12F3LF | KE-50LF | KE-25F3LFM
Features: Standard product | Fast response | Long life | Measurable up to 100% O2
Measurement range: 0–30% O2 (KE-25LF / KE-25F3LF / KE-12F3LF / KE-50LF) | 0–100% O2 (KE-25F3LFM)
Initial output voltage: KE-25LF / KE-25F3LF: 10–15.5 mV | KE-12F3LF: 9–15 mV | KE-50LF: 4.5–7.5 mV | KE-25F3LFM: 5–8 mV
Accuracy (% FS): KE-25LF / KE-25F3LF: ±1% | KE-12F3LF: ±1% | KE-50LF: ±2% | KE-25F3LFM: ±1%
Operating pressure: 811–1216 hPa (all models)
Operating temperature: 5–40 °C (all models)
90% response time: KE-25LF / KE-25F3LF: approx. 15 s | KE-12F3LF: approx. 8 s | KE-50LF: approx. 60 s | KE-25F3LFM: approx. 15 s
Life expectancy (O2% × Time h): KE-25LF / KE-25F3LF: approx. 90×10^4 %h (≈5 years) | KE-12F3LF: approx. 55×10^4 %h (≈3 years) | KE-50LF: approx. 180×10^4 %h (≈10 years) | KE-25F3LFM: approx. 108×10^4 %h (≈6 years)

Notes
1) Product specifications are subject to change without notice. 2) "Lead-free" indicates lead content ≤ 0.1 wt% in each homogeneous material making up the product. Life expectancy values assume usage at 20 °C, 60% RH and 1013 hPa and are expressed as (O2 concentration %) × (time h).

Technical specifications

• Series: KE-LF (lead-free galvanic cell-type oxygen sensors)
• Measurement ranges: 0–30% O2 and 0–100% O2 (model dependent)
• Initial output voltages by model: 4.5–15.5 mV (model dependent)
• Accuracy: ±1% FS (most models); ±2% FS (KE-50LF)
• Operating pressure: 811–1216 hPa
• Operating temperature: 5–40 °C
• Response time (90%): 8–60 s depending on model
• Life expectancy: approx. 3–10 years depending on model (expressed as %O2 × hours)
• No external power required; stable output voltage; minimal CO2 influence due to weak-acid electrolyte