TEN
TEN Automotive Equipment Ltd.
©
Page 7
Version 5.0 November 2010
4 Principle and operation
The fundamental principle of the Gasbench, where the exhaust gas is guided through for measurement, is based on
non dispersive infrared absorption, also known as NDIR. While the Gasbench emits infrared light through the
measuring chamber, certain gasses are absorbing the light. This level of absorption gives a direct lead of the gas
concentration in the measuring chamber. Every gas absorbs the infrared light at a different frequency area. The
Gasbench is fully digital and with its own microcontroller it calculates, compensates and linearizes every gas value.
The following gas components are found in the exhaust emissions of motor vehicles equipped with an electrical
ignition. The INNOVA 3000 provides simultaneous measurements of:
- CO carbon monoxide
- CO
2
carbon dioxide
- HC hydro carbons
- O
2
oxygen
In addition to the infrared gasbench the INNOVA 3000 is also equipped with an electro-chemical sensor which
measures the oxygen concentration in the sampled exhaust gas. With the data from both the oxygen and infrared
Gasbench readings, a lambda calculation is made. This so called lambda value gives an indication about the
efficiency of the combustion, i.e. if the engine is running too rich or too lean.
The RPM meter of the INNOVA 3000 is interrupt triggered and, as a result, is very accurate. After intricate filtering
of disturbances and interference the pulse or signal is directed to the microcontroller which calculates the pulse into
a numeric value. This technique offers a smart solution to easily select the RPM sensor used and appropriate
division factor.
The Oil temperature probe is equipped with a heat sensing semiconducting resistor. As the temperature of the
sensor changes, also the resistor value of the sensor changes so every change in Oil temperature can be
determined.
