The value of the fast response measurement of Air-Fuel ratios (AFR) has long been appreciated in the study of both
fuel delivery systems and in-cylinder combustion processes.
The CUSSONS Lamdascan principle is a well established one. Exhaust sample gas is taken from a source, passed through a heated sample line and diluted with an accurately metered quantity of ‘dope’ gas, which is usually ambient air. The diluted sample is oxidised over a platinum catalyst and passed to a high temperature zirconia cell. Residual oxygen, which is directly proportional to the engine AFR and the known quantity of dope gas, is measured by the zirconia cell.
Bottled gases (oxygen and nitrogen) may be used in place of the dope air when it is considered that the ambient air is sufficiently contaminated with carbon monoxide or hydrocarbons to cause inaccurate measurement.
Heated sampling prevents condensation of any hydrocarbon compounds and water vapour, and so increases accuracy and durability. 

Statistical functions (Average Value, Standard Deviation, and Peak to Peak), are obtained over a 30 second sampling
time, and are shown as the Equivalence Ratio (Lambda), or Air-Fuel Ratio, dependent upon display selected.
Automatic range change by dope gas switching ensures that the zirconium cell is operating at optimum oxygen concentration, and thus at best accuracy. AFR results from 5:1 to 50:1 may be obtained without loss of test data. Range changes may also be selected manually.
The GPIB (IEEE 488) is a standard feature which suits most forms of computer interface, and permits several Lamdascan sample handling units to be controlled from one master Lamdascan control unit. This feature is particularly useful for investigating transient mixture distributions.
Pre-set programs are selectable by positive action push button switches. The hinged front panel of the controller opens to allow access to switches for hydrogen/carbon (HC) and oxygen/carbon (OC) ratios of the fuel used, oxygen/nitrogen ratios of dope and reference gas - normally air, and external analogue signal zero and span settings.

Critical pressures are displayed on gauges on the sample handling unit to allow monitoring of correct operating conditions.

MEASUREMENT RANGE：5–50 AFR by four steps. Automatic range change mode selectable

ACCURACY：± 0·04% volume of O2 which is typically equivalent to better than ± 0·1 AFR, ± 0·005l
STABILITY：Better than ± 0·02% volume O2 over 2 hour measurement period
RESOLUTION：± 0·01% volume O2, ± 0·01 AFR, ± 0·001l
REPEATABILITY：Better than ± 0·02% volume O2. Typically equivalent to better than ± 0·05 AFR, ± 0·003l
LAG TIME WITH 3M HEATED LINE：Less than 500 milliseconds
RESPONSE RISE TIME WITH 3M HEATED LINE： Air to Nitrogen; 90% change in less than 300 milliseconds without digital frequency compensation.

EXHAUST SAMPLE INLET PRESSURE; TOLERANCE ：–200 mbar to +1 bar, resulting ± 0·003l at low dope, ±
0·01l at high dope
EXHAUST SAMPLE FLOW:：Approximately 5 litres per minute
EXHAUST SAMPLE TEMPERATURE：For 0º to 400ºC use Models P9121 of P9123  For –40º to 100ºC use Models P9116/7 or P9124
WARM UP TIME：60 minutes
TYPICAL CATALYST LIFE：500 hours unleaded fuel, 50 hours leaded fuel
AMBIENT TEMPERATURE：0 to 50ºC
RECORDER OUTPUTS (STANDARD) ：0 to 1V = 0 to full scale for l/AFR/O2 ；0 to 1V º 0 to 10% O2
COMPUTER INTERFACE：GPIB (IEEE 488) standard
HC RATIO ADJUSTMENT RANGE ：0·00 to 9·99
OC RATIO ADJUSTMENT RANGE ：0·00 to 9·99
HEATED SAMPLE LINES ：3 metres length standard, 1, 5, 8 or 10 metres, options directly interchangeable
CONNECTING CABLE - CONTROL UNIT TO
SAMPLE HANDLING UNIT ：17 way x 6 metre long. Other lengths 1 to 25 metres to order
SAMPLE FILTER ：19 mm x 90 mm Whatman extraction thimble
ELECTRICAL POWER REQUIREMENTS ：Single Phase, 2·8kW, 100-120/200-240V, 50/60Hz
GAS SUPPLIES
Purge Air 10 litre/mm at 2 to 6 bar
N2 Zero Gas 5 litre/mm at 2 to 3 bar
O2/N2 Cal Gas 5 litre/mm at 2 to 3 bar

¨ Fast Response Time with High Accuracy
¨ Automatic Range Change and Calibration
¨ Operation on all HC and Alcohol Fuels
¨ Externally Controllable
¨ Built-in Statistical Functions
¨ Heated Sampling for Durability and Accuracy
¨ Wide Sample Pressure Tolerance
¨ GPIB (IEEE 488) Interface as Standard
¨ Simple to Operate, with Pre-set Programs
¨ Microprocessor Based