Principle - Flame Ionisation detection method (FID) with selective combustion

The flame ionisation detection method (FID) --- used in combination with the selective-combustion system--- utilises the ionisation that occurs as the result of the high-temperature energy from combustion at the tip of the burner jet when organic carbon com-pounds are introduced into the hydrogen flame. The hydrogen flame is located between two electrodes. When an electrical voltage is applied across these electrodes a minute ion current proportional to the hydrocarbon concentration is produced. This current is monitored by a low leakage amplifier, giving a voltage readout for THC. To measure CH4 the sample gas is passed through the selective catalytic combustion unit (the NMHC cutter), which oxidises NMHC without oxidising CH4. This is shown as A below. B represents the THC concentration measured without passing the gas through the NMHC cutter. Thus B - A will give the concentration of

NMHC. The final concentration value is calculated using a relative sensitivity correction coefficient, k, as shown below.

CH4 Concentration A

NMHC Concentration k (B - A)

THC Concentration A + k (B - A)

The highly sensitive, highly accurate, and minimal-maintenance APHA-360 provides precise atmospheric pollution monitoring data.

The APHA-360 has TA-Luft approval.

Ambient HC Monitor

APHA-360

Features


The APHA-360 uses a combination of the flame ionisation detection method and selective-combustion. This gives it the advantages of the single- detector method plus the ability to do continuous, zero-drift free measurements of THC, NMHC, and CH4. The design gives great stability and high sensitivity (F.S. 5 ppm). The APHA-360 has a relative-sensitivity correction function for CH4 and NMHC.


A catalytic unit for generating reference gas and auxiliary combustion air is standard equipment in the APHA-360.


All the necessary features are built into a single rack sized instrument, including a catalytic unit for selective combustion (i.e., an NMHC cutter); a catalytic unit for generating reference gas and auxiliary combustion air; and a sampling pump.

The only supplemental gas required is hydrogen.