Epc Detector; Manually Controlled Detector - Agilent Technologies 6890 Series Service Manual

Gas chromatograph

Hide thumbs Also See for 6890 Series:

Table of Contents

Thermal Conductivity Detector (TCD)

Theory of operation

EPC detector

The EPC TCD has one flow line for the makeup/reference gas. After an initial

filter frit, it splits into two paths. Each line has a proportional valve controlled

by a pressure sensor, and a non-adjustable restrictor frit. In addition, the

switching gas line has a switching valve that switches paths through the TCD

cell several times a second. The switching line oscillates between two

flowpaths, one for each channel of the TCD cell. The makeup gas line sweeps

past the end of the column and carries the column effluent into the TCD cell.

reference gas in

Proportional

control loops

Figure 330-4

EPC TCD flow diagram

The manually controlled TCD has a pneumatic supply line for the switching

gas (also called modulating or reference gas) flow and one for the makeup

gas. Both of the lines have pressure regulators, an on/off solenoid valve and

a non-adjustable restrictor frit. In addition, the switching gas line has a

Agilent 6890 Gas Chromatograph Service Manual

6890a 6890 plus