The effort in manpower and equipment and the expense in money and time involved in carrying out the various emissions tests have considerably increased over the past years. The same holds true for the fuel economy measurements. The present-day emissions testing practice calls for complex gas sampling and dilution systems (CVS) and for a big variety of different analyzing devices. The development of a unique instrument with which the interesting emission components can be measured simultaneously and directly behind the exhaust pipe would mean a decisive improvement of this situation. In an intensive study possible measurement methods were compared and a way was pointed-out to construct such an instrument.