Arduino shield: Bosch LSU 4.9 wideband sensor (for AFR measurement)

When dealing with the combustion of fuel, one of the important factor is controlling the fuel-to-air mixture ratio. The combustion process itself is - to put simply - a chemical reaction of rapid oxidation. A correctly selected proportion between fuel and air - often called a stoichometic value - means, the combustion process uses the entire mass of fuel and mass of oxygen particles in the volume.

Wideband O2 sensors are used for determinig the AFR (air-to-fuel) ratio.

The presented module is based on the Bosch CJ125 integrated circuit. It is an advanced circuit, that incorporates:

• O2 measuring circuits (a set of precise, programmable amplifiers)
• O2 sensor supervising block
• digital, programmable unit for communication with processor via SPI bus

The CJ125 can operate in a very wide temperature range, from -40 up to 150 centigrades.

The presented module is an implementation of the CJ125 circuit in a premium setup:

• the CJ125 measuring circuits are built on a very precise resistors with a tolerance of 0.1%, giving superior accuracy
• includes a PWM controller to control the sensor's heater

The module is supported by the arduino-cj125 library, which can be found on the Git Hub server (link can be found in a Git Hub tab). The library has ready-made functions that ensure:

• correct startup of the O2 sensor (easy to damage with incorrect startup due to a water condensation or overheating)
• calibration of the measuring system
• sensor fault detection
• heater support in PWM mode

Please note, the Bosch LSU 4.9 wideband sensor is not included, it has to be purchased deparately.

arduino-cj125 library on Git Hub (opens a new window)