Additional tidbits of information
Drift and noise are affected by numerous variables. GOW-MAC quality control procedures ensure superior detector performance, by precise matching of filaments and thermistors over an extended current-resistance curve and under controlled heat dissipation conditions. Compatible filament pairs are installed symmetrically in a cell block. Under conditions of constant cell current, cell block temperature, carrier gas flow and pressure, negligible drift and noise will be noted on a 1 mV potentiometric recorder. The signal can be amplified many times under such precisely controlled conditions.
Oxidation and Corrosion Resistance
Thermal conductivity detectors (TCD) can be supplied with gold-sheathed tungsten, rhenium-tungsten, nickel, or other special filaments installed in cell blocks of Monel, etc.
Gas Density Detectors (GADE
) with elements in the inert reference stream are not exposed to the sample and are capable of long service life with highly corrosive samples.
Sensitivity of hot wire thermal conductivity detectors (TCD) depends on the internal geometry, type of detector elements, and the temperature differential (D
t) between filaments and cell block. Thermistor detectors are at their best in sub-ambient and ambient operation. Experiments with filament and 8K thermistor detectors of identical geometry demonstrate that greater signal is obtained from the hot wires at cell temperatures of 75 °C and above.