Emerson 700 XA User Manual

After the equipment/software has been installed and the operation stabilized, automatic
operation can be initiated via an ethernet network.

1.5

Theory of operation

The following sections discuss the theory of operation for the GC, the engineering
principles and the concepts used.

Note

See

Section 1.7

for definitions of the terminology used in the following explanations.

1.5.1

Thermal conductivity detector

One of the detectors available on the 700XA is a thermal conductivity detector (TCD) that
consists of a balanced bridge network with heat sensitive thermistors in each leg of the
bridge. Each thermistor is enclosed in a separate chamber of the detector block.

One thermistor is designated the reference element and the other thermistor is
designated the measurement element. See

Figure 1-2

for a schematic diagram of the

thermal conductivity detector.

Analyzer assembly with TCD bridge

Figure 1-2:

Introduction

Introduction