Direct Digital Lambda (DDL)
Wide-Band Exhaust-Gas-Oxygen Sensor

A Wide-Band O₂ Sensor

The Bosch wide-band sensor (LSU) and the NTK/NGK wideband sensor is actually comprised of four distinct sections: Reference Cell Nernst Cell Pump Cell Heater Very little hard, detailed information about how the sensors are supposed to be driven is readily available. The pump cell current required to maintain a relative voltage output of 0.45V between the measurement cell and the reference cell, is a measure of lamba, the fuel-air ratio. An integrated heating element is used to maintain a minimum cell operating temperature of 600 C. Upper temperature limit is typically 800 C. A stable sensor temperature is desirable as it's characteristics vary significantly with temperature. Any data referred to herein are based on the following references and should not be applied to any other type of sensor. References (German): Bosch: Kraftfahr Technisches Taschenbuch 22. Auflage 1998 ISBN 3-540-62219-5 Bosch: Ottomotor-Management 1. Auflage 1999 ISBN 3-528-03877-2 English equivalents Bosch: Automotive Handbook 5th Ed. 2000 ISBN 0-7680-0669-4 Bosch: Gasoline Engine Management 1st Ed. 1999 (the author has not seen this book) ISBN 0-7680-0510-8

Illustration from (German) Bosch Automotive Handbook

www.tagelectronics.co.uk have some data including:

• Range 10 to 30AFR (lambda 0.69 to 2.06)
• Air fuel ratio (AFR) is based on propane for which stoichiometric mixture is 14.57:1
• Accuracy without software correction
  • AFR 14.57 <±0.005
  • AFR between 12 & 18 <±0.69
  • AFR <12 or >18 <±2.3
• Warm up time 30s in air with no gas flow
• Response time (to reach 50% of final value after a step change) 330ms typ.
• Thermal shift <±0.6AFR/100K change in tip temp.
• Ageing shift after 500hrs cycling between 300 & 800°C, 12 to 18AFR
  • AFR 14.57 ±0.01
  • AFR between 12 & 18 ±0.25
  • AFR <12 or >18 ±0.40
• Pumping current must be kept within ±10mA
• Cell supply voltage 450±10mV
• Heater supply voltage 10.5±0.5V
• Heater resistance >2.7 to 3.3 ohm@25°C, 9.0 ohm @800°C
• Calibration interval 500hrs
• Resistant to standard motorsport fluids
• Average humidity 5 to 10% absolute volume
• Gas temperature 25 to 800°C
• Operating temperature (the heater must be operating correctly to ensure accurate readings)
  • Sensor tip 700 to 900°C
  • Body at mounting hex <550°C
  • Body at cable outlet <200°C
• Rate of temperature change must not exceed 50K/s. Temperature shocks must be avoided.

• Bosch: ME-Motronic Engine Management
  Bosch Number: 1 987 722 178 Document Code KH/PDI2-09.99-En
  ISBN 0-8376-0611-X

  The booklet describes the application and use of the sensors, omitting any crucial numbers required for DIY. You can download it from http://www.sae.org for a small charge or purchase it through another source such as http://www.rb.com. Note that much of what appears in the ME-Motronic instruction booklet appears in the Gasoline Engine Management book.

• US Patent 6,120,677 "Temperature Control for All Range Oxygen Sensor", Yamada, et. al. (NGK) , Sep 2000.
• US Patent 5,312,538 "Device for Controlling the Electrical Power Supply of an Oxygen Pump of a Linear Oxygen Probe", Metrich (Siemens), May 1994.
• SAE 1999-01-0202 "Long Term Stable NOx Sensor with Integrated In-Connector Control Electronics", Nobuhide Kato and Nobuyuki Kokune (NGK Insulators, Ltd) Bertrand Lemire and Tim Walde (Siemens AG)