Humberto:

A BAR 90 is a 4 gas analyzer. It measures HC, CO, CO2 and O2. The BAR 97 is a 5 gas that measures HC, CO, CO2, O2 AND NOx.

The two analyzers are identical except the BAR 97 has a NOx cell next to the O2 cell and a preamp for the NOx information. ... Login to read more.