The choice of the correct combustion analyzer is not simple due to the number of different models and makes of combustion analyzer presently on the market. These are also of widely differing price and complexity. Naturally, every company wants to have the best combustion analyzer for the purpose, but that does not necessarily mean the most expensive! This short guide to choosing a combustion analyzer should help to answer some of the more common questions that are often not asked, but should be. Regrettably, many companies are more intent on their own profits, rather than providing the best solution for the customer. Naturally, there are quality differences between some combustion analyzers, which are often (but not always!) reflected in the price. A cheap emissions analyzer will often turn out to be more expensive in the long run, especially as some companies will sell a combustion analyzer at a low price, but recover the difference with service costs. Available accessories and support are also matters that make a great difference to the choice.
These are the first questions to be asked:
Question 1. is, perhaps, the most obvious from the list:
The GA-12 combustion analyzer can be fitted with up to 3 sensors, which is quite standard for test s on residential equipment.
The GA-20plus combustion analyzer can also be fitted with up to 3 sensors, although the ranges are different for the two instruments.
The GA-21 plus can be fitted with up to 9 sensors, including two infrared sensors.
The GA-40(T) plus combustion analyzer can also be fitted with up to 9 sensors.
The GA-60 can be fitted with up to 8 sensors.
Which sensors are standard, and which can be fitted optionally can be seen in the price-list.
The sensors should not be combined freely due to the necessity of compensating the cross-sensitivities for foreign gases in the combustion analyzer, unless there is good reason to believe that there are no other interfering gases.
Question 2. must now be answered.
Smoke measurement is standard on the GA-20plus, GA-21plus, GA-40plus and GA-60, not available on the GA-12 combustion analyzer.
The heated hose now has a special adapter for the soot test, so this is possible on later versions of the GA-40Tplus combustion analyzer. Alternatively, a separate probe holder can be ordered to carry out smoke tests.
It must be compatible to the probe used and fitted with a heating element.
To carry out the soot test the appropriate probe holder must be ordered, and the heating element only works when the analyser is connected to the mains.
Question 3. is very important.
All flue gases contain moisture. If this water condenses in the piping or in the combustion analyzer, then damage may occur to the electrochemical cells, fogging or water damage to the infrared sensors is likely and certain gases will be absorbed before reaching the measuring cells, which naturally falsifies the results. The analyser is fitted with a water trap, which is sufficient for sampling purposes but cannot cope with continuous measurement. The solution to this problem is a gas dryer, preferably in combination with a heated hose. A rough comparion carried out with two different combustion analyzers, one fitted with a dryer and the other without showed a difference of about 20 % in the values of SO2 measured with and without dryer.
For use with a heated hose, the probe holder is replaced either by a heated filter or the special connector. These must be ordered separately for the GD-10, but are standard with the GA-40Tplus. The gas absorption is especially noticeable for NO2 and SO2, which should be measured using a dryer.
The longer a measurement takes, the more condensation is to be found in the sample line, which will absorb these gases very quickly.
The mini-dryer is very effective in protecting the instrument but, without a heated hose the increase in accuracy is not very high.
Condensate is incidentally a problem for all combustion analyzers, however much the manufacturers deny it.
Question 4. is very simple:
The GA-12 and GA-20plus combustion analyzers are not fitted with analogue outputs, so they cannot be used with such recorders. They are available as an optional extra on the GA-21plus, GA-40(T) plus and GA-60.
Question 5. narrows the search down, too.
The GA-60 may only be equipped with an external ambient temperature sensor, GA-40plus and GA-20plus have two inputs each for current and voltage, together with inputs for two thermocouple and two thermoresistive channels The GA-12 combustion analyzer does not have this option.
Question 6. is more a question of convenience.
The GA-60, GA-40(T)plus and GA-21plus all have built in printers,
whilst the GA-12 and GA-20plus combustion analyzers require an external printer.
Question 7. is the decision about the use of a heated casing.
This option is only available on the GA-60 combustion analyzer. Excessively low temperatures have a bad affect on the functioning of the electrochemical and infrared cells.
All the analyzers are equipped with serial interfaces allowing readout of data and data processing on a computer using the software supplied. There is a full version of the software available for the combustion analyzers, which has further options.
The other optional extras are common to all the analyzers.
The combustion analyzer comes complete with User's Manual, filter elements, mains cable (where appropriate) and printer paper (where appropriate), ready for use.