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Principle of operation
The FIDAMAT 6 carries out substance-specific measurements and not component-specific measurements. It measures the total of all hydrocarbons in a sample gas, but with different weighting of the hydrocarbon molecules. To a first approximation, the display is proportional to the number of C atoms in the respective molecule. However, there are fluctuations in practice. The display deviation for the respective molecule is expressed by the response factor.
The sample gas is supplied to the FIDAMAT 6 through overpressure or drawn in by the built-in diaphragm pump (optionally via a heated line and an additional filter) and passed on to the flame ionization detector via an obstruction-proof fused-silica restrictor.
In the detector, the hydrocarbons in the sample gas are burned in an oxyhydrogen gas flame. Burning partially ionizes the proportion of organically-bound hydrocarbons. The released ions are converted into an ionic current by the voltage present between two electrodes, and measured using a highly sensitive amplifier. The current measured is proportional to the quantity of organically-bound C atoms in the sample gas.
A pressure regulator keeps the combustion gas pressure constant. The balanced system of pump, capillary tubes, and pressure regulator for combustion air ensures that the sample gas pressure is kept constant.
When the analyzer is switched on, ignition is carried out automatically when the setpoint temperature has been reached and, for versions "with pump", the pump is also started up.
FIDAMAT 6, principle of operation
The FIDAMAT 6 provides various messages in the form of floating contacts:
- Maintenance request
E.g. sample gas flow (filter/pump)
Fan failure (advance warning for measuring accuracy)
The measured value remains unaffected. - Fault
E.g. hydrogen, combustion air and sample gas pressures, temperature, analyzer part and pump, fault in the electronics (temperature).
The measured value may be influenced. - Failure
In the event of failure of, for example, the electronics, power supply, combustion gas, combustion air or sample gas, the analyzer automatically shuts down (the combustion gas valve is closed).
Note
The sample gases must be fed into the analyzers free of dust. Condensation should be avoided. Therefore appropriate gas preparation is required for most applications.
Essential characteristics
- Four freely parameterizable measuring ranges, also with suppressed zero, all measuring ranges linear
- Galvanically isolated measured-value output 0/2/4 to 20 mA (also inverted)
- Autoranging possible; remote switching is also possible
- Storage of measured values possible during adjustments
- Measuring range identification
- Measuring point switchover for up to 6 measuring points
- Measuring point identification
- Wide range of selectable time constants (static/dynamic noise suppression); i.e. the response time of the device can be adapted to the respective measuring task
- Easy handling thanks to menu-driven operation
- Low long-term drift
- Two control levels with their own authorization codes for the prevention of accidental and unauthorized operator interventions
- Automatic range calibration can be parameterized
- Operation based on the NAMUR recommendation
- Customer-specific analyzer options such as:
- Customer acceptance
- TAG labels
- Drift recording
- Wear-free, corrosion-proof filter housing
- No blocking of the sample gas capillaries through the use of a quartz restrictor
- Purge function in the event of analyzer or power supply failure (avoids build-up of toxic and corrosive substances in the device)
- Low consumption of combustion air
- Response factors comply with the minimum requirements in accordance with German air purity guidelines and the Working Group of the German automotive Industry
- Simple handling using a numerical membrane keyboard and operator prompting
Response factors (examples, mean values)
|
Substance |
Mean response factor |
|
n-butane |
1.00 |
|
n-propane |
1.00 |
|
n-heptane |
1.00 |
|
Cyclohexane |
1.08 |
|
Isopropanol |
0.81 |
|
Toluene |
1.06 |
|
Acetone |
0.92 |
|
Ethyl acetate |
0.76 |
|
Isobutyl acetate |
0.83 |
|
Methane |
1.06 |
|
Ethane |
0.99 |
|
n-hexane |
1.01 |
|
iso-octane |
1.04 |
|
Ethine (acetylene) |
0.91 |
|
Propene |
0.84 |
|
Methanol |
0.87 |
|
Ethanol |
0.83 |
|
Ethanoic acid |
1.13 |
|
Methyl acetate |
0.67 |
|
Benzene |
1.01 |
|
Ethyl benzene |
0.96 |
|
p-xylene |
1.03 |
|
Dichloromethane |
1.13 |
|
Trichloroethene |
1.01 |
|
Tetrachlorethene |
1.07 |
|
Chloroform |
0.72 |
|
Chlorobenzene |
1.15 |
Cross-interferences (examples)1)
|
Interfering component |
Concentration of the interfering component |
Induced cross-interference |
|---|---|---|
|
O2in N2 |
(21 vol. %) |
< 0.3 mg/m3 |
|
SO2 in N2 |
(258 mg/m3) |
< 0.15 mg/m3 |
|
NO in N2 |
(310 mg/m3) |
< 0.5 mg/m3 |
|
NO2 in synth. air |
(146 mg/m3) |
< 0.1 mg/m3 |
|
CO in N2 |
(461 mg/m3) |
< 0.15 mg/m3 |
|
CO2 in N2 |
(18 vol. %) |
< 0.1 mg/m3 |
|
HCl in N2 |
(78 mg/m3) |
< 0.3 mg/m3 |
1) With measuring range 0 to 15 mg/m3.