The Model T400 UV Absorption analyzer uses a system based on the Beer-Lambert law for measuring low ranges of ozone in ambient air.

A 254 nm UV light signal is passed through the sample cell where it is absorbed in proportion to the amount of ozone present. Periodically, a switching valve alternates measurement between the sample stream and a sample that has been scrubbed of ozone. The result is a true, stable ozone measurement.

All T Series instruments offer an advanced color display, capacitive touch screen, intuitive user interface, flexible I/O, and built-in data acquisition capability. All instrument set up, control and access to stored data and diagnostic information is available through the front panel, or via RS232, Ethernet, or USB com ports,​​​ either locally or by remote connection.

The Model T400 comes with NumaView™ Software. NumaView™ Remote PC Software allows for a remote connection with virtual interface and data downloading capability to analyzers operating NumaView™ Software.​