E C O P H Y S I C S Introduction
CLD 780 TR / July 2000 2
1.1 Introduction
The CLD 780 TR is the first commercially available NO analyzer which is
designed and developed specifically for airborne applications. It need
hardly be said that this new instrument delivers fast, continuous, highly
specific NO concentration data which is linear over all the measurement
ranges.
Analyzers using classical chemiluminescence techniques are not capable
of accurately measuring NO at concentrations of below a few ppb. Apart
from the inadequate detection limit of these instruments, they also suffer
from interferences caused by other components in the sample gas (e.g.
OH radicals, and a large number of hydrocarbons) which can produce
errors of several ppb. The design of the CLD 780 TR is based to a large
extent on the proven “fore-chamber” principle used by its predecessor in-
strument, the now legendary ECO PHYSICS CLD 770 AL ppt. The ad-
vanced fore-chamber construction in the CLD 780 TR ensures the elimina-
tion of interferences due to hydrocarbons and OH radicals.
The CLD 780 TR also achieves new levels of performance in terms of sig-
nal processing, instrument control, user-friendliness and problem diagnosis
thanks to the consistent use of leading-edge processor technology. The
serial interface allows the user not only to monitor the measurement data
and any error messages on an external display screen, but also permits
all instrument operating steps such as calibration, measurement range
switching and monitoring of diagnostics via computer.
Zero point compensation is performed automatically in the CLD 780 TR
without the need for a supply of zero air. The problems caused by con-
densation around the photomultiplier socket, which plague many chemi-
luminescence-base analyzers on the market, are avoided by the use of a
dry air flow around the cooled PMT housing.
The operation the CLD 780 TR is quickly grasped by the new user, the
menu-based control dialog between the keypad and the display being
self-explanatory. Despite this, we recommend that you read the following
chapters carefully to learn about the multifaceted capabilities of this
unique instrument.
As with the CLD 770 AL ppt, the CLD 780 TR is intended, if required, to
be used together with a photolytic converter. The combined operation of
CLD 780 TR and PLC 762 is therefore covered in Chapter 5 (Operating
Instructions), Chapter 6 (Calibration) and Appendix A3 (Gas Phase Titra-
tion etc.). Detailed information regarding the PLC 762 itself can be found
in the PLC 762 Operator’s Manual.
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