Madur Gas Analysers

The small ones:

GA-12 and GA-12plus
The GA-12 is designed with two or three sensors, with O2and CO as standard model and an optional NO sensor. This cannot be realistically added later. The instrument comes complete with carrying case, batteries (non-rechargeable), RS232 cable for computer connection and probe. Options include a rubber protector for the instrument and the printer shown here. If needed, longer probes are available. The instrument is mostly used for checking and adjusting smaller oil or gas burning combustion systems. The instrument can also be used with a pitot tube to measure flow velocity and can be fitted with a humidity probe. A graphic display is standard and backlighting is available as an option, as is an external ambient temperature sensor or a relative humidity probe. A magnetic holder can be fitted to the instrument to attach it to ferrous surfaces. There is also a mains power unit, for those who use the analyser for long periods attached to the computer. This is not a battery charger.
The GA-12plus was designed for use with up to four sensors. It is slightly larger than the GA-12. The basic version has two sensors, O2 and CO. It can be fitted with a sensor for NO, and then there is space for an extra sensor, either NO2 or SO2. These can only be added if the NO sensor is fitted. The instrument has the capability of carrying out a soot test according to the Bacharach method. The pump flow rate is electronically controlled to allow this to be carried out accurately. It is fitted with a rechargeable battery and comes complete with charger. The instrument is delivered as standard in a carrying case with probe (300 mm) and probe holder for the soot test. There is an option for a differential pressure sensor to measure either pressure differences or, using a pitot tube, flow velocity. An external ambient temperature sensor can also be added if necessary. Longer probes can be substituted if needed by the application. A magnetic holder is also available for this analyser. This instrument is designed for similar applications as the GA-12, with the addition of an extra sensor and the soot test option.
Both instruments have an interface for an external infrared printer. This will also fit inside the carrying case. This printer uses rechargeable batteries and comes complete with charger. All the screens on the display can be printed and the main printout can be configured by the user, as can the display itself. Like all the larger analysers, these hand-held instruments are equipped with a software based cross-sensitivity calculation to remove any interference effects between the sensors. Electrochemical sensors typically react to other gases in addition to the primary target gas, although to a lesser extent. These effects can be registered in the calibration phase and used later during measurements to cancel out the cross-sensitivities to a great extent.

The medium sized analysers

GA-21plus
This is a portable analyser available either in a soft case or hard case. It was originally designed to take 4 electrochemical sensors and a further two infrared sensors for methane and carbon dioxide. Nevertheless, it is now possible to extend the range of sensors fitted, and it can be fitted now with up to nine electrochemical sensors in addition to the two infrared units. Without the cross-sensitivity calculation this would not be practicable. It can either be supplied in a hard case as shown or in a soft carrying case. The standard model contains O2 and CO, all other sensors can be chosen as options from the list. A dot matrix printer is fitted to the analyser. The instrument can be fitted with extra filters (shown) or a minidryer (shown) to remove condensate from the gases and improve the lifetime of the sensors. Other options include an external ambient temperature sensor, a graphic display of results and a programmable purging pump to prevent over-range of the CO sensor. The differential pressure sensor is standard equipment and can be used for flow velocity measurement with additional optional software and a pitot tube. The capability for the soot test is standard, but an appropriate probe holder must be taken to use this option. Only the heated probe holders can carry out the soot test. The instrument has an alphanumeric keyboard to allow letters and numbers to be entered simply. The instrument is built around a pressed and fabricated steel rack to ensure strength and stability.

GA-40plus
The GA-40plus is very similar in design to the GA-21plus. It comes with O2 and CO as standard, and the graphic display together with the purging pump are also standard here. The instrument is also equipped with a range of extra analogue inputs for temperature, voltage and current. The analyser uses the same display as the GA-21plus which is fitted with a high grade backlighting. This can be switched off if not needed to extend the life of the battery. Two analogue outputs can be fitted to the analyser if needed. All the options available with the GA-21plus are available here, or are standard equipment, such as the two filters, which are normally fitted here. For accuracy of results, the cross-sensitivity calculation is standard, as in all other analysers. Naturally the analyser can be supplied for 110 VAC or 230 VAC as required. The casing of the analyser was designed to be within airline hand-luggage limits to make life easier for travelling service technicians. As with the GA-21plus, the printer will produce both graphic and text results. Since this is a dot matrix printer, the results will not fade as quickly as a printout made on thermopaper.

The bigger analysers

GA-40Tplus
The GA-40Tplus is very similar to a GA-40plus with the addition of an integrated peltier cooler and a heated hose. This equipment ensures that the gases remain above the dew point between sampling point and analyser. In the peltier cooler they are quickly cooled down to ensure rapid condensation. The condensate is removed by an integral peristaltic pump. This procedure is designed to limit the contact between the gases and condensate, which can result in removal of NO2 and SO2, which are both highly soluble gases. This also provides very good protection for the infrared sensors if fitted. Condensation inside the infrared sensors will lead to failure of the units. The standard heated hose is powered by mains power to ensure efficient heating. There is an adapter available to enable a soot test to be made with this instrument. The heated hose and gas drier in combination with the cross-sensitivity calculation ensure and accurate measurement of the soluble gases such as SO2 and NO2. This analyser can also be used for long-term measurements with programmable measuring phases and purging phases. This provides a capability to cover some of the modern requirements for long-term measurements and a useful back-up to fixed installations.

GA-60
The GA-60 has been around in one form or another for many years. Due to continuous updating it has remained state of the art despite its age. This was the first analyser to have the cross-sensitivity calculation. The instrument has O2, CO, NO, NO2 and SO2sensors as standard. Another electrochemical sensor can be fitted and up to two additional infrared sensors. This analyser can also be used in combination with the GD-10, providing a semi-continuous capability. This should not be practiced without a dryer due to the dangers of condensate accumulation in the analyser. The analyser includes a large, backlit LCD screen and all standard features such as RS232 communication and storing of results. A soot test is also possible if the correct probe holder is used. There is also an option for 6 freely programmable analogue outputs for this instrument, and a case heating module for use in cold climates. The construction on separate, exchangeable PCBs makes this instrument a favourite of all service technicians. Like all the instruments, an internal battery serves to operate the instrument without connection to the electrical supply. The large battery in this instrument does have a negative side; the GA-60 is relatively heavy, but can operate for at least 8 hours without external power.

The gas dryers

GD-10
The GD-10 has also been one of the main products for a long time. It is a gas cooler/dryer based on a peltier element that rapidly cools the gases down from the dew point to around 4°C, causing fast condensation of the water that is always present in flue gases. The peristaltic pump will rapidly remove the condensate formed to reduce its contact time with the gases to a minimum. The instrument is fitted with a controller for the heated hose and the dryer unit, allowing the hose temperature and the cooler temperature to be set as needed. The connection cable between dryer and analyser is compatible with all the analysers and will transfer the gas temperature and ambient temperature information to the analyser. The dryer is fitted with a gas pump to allow the longer gas transfer distance. The heated hoses are available in various lengths up to 5 metres. Longer hoses will require a separate hose controller due to the power necessary to heat them. The heated hose needs about 100 W per metre of length in normal operation.

PGD-100
The PGD-100 is a further development of the GD-10. It is designed specifically for use with the Photon analyser, but may be used with any of the other analysers if needed. It can be operated remotely from the Photon over the comm-unication cable. This dryer uses a two-stage peltier drying unit to ensure a constant level of remaining humidity. No drier can remove all of the water, but a constant and small level of remaining condensate ensure that the effects can be cancelled out in the software. The PGD-100 can naturally also be used with the other analysers, but communication between analyser and drier is only possible with the Photon. This drier has all the same features as the GD-10, simply being based on a two stage peltier drying unit.

The gas monitors
The maMoS family of gas monitors is designed for use in industry and is very different to our other instruments. These are fixed systems providing simple control and monitoring of industrial processes. The typical uses include biogas operations, waste water treatment and all areas where a specific gas concentration is used as the main operating parameter. All of the instruments are fitted with a powerful peltier cooler to remove condensate from the gases. This includes a visible external filter which can be easily checked for maintenance purposes. The instruments have analogue outputs for current and voltage for each measured gas. There is also a digital output for integration in a control system or display of the values on a computer. The software supplied with the monitors will allow the user to set purging and operation times, carry out calibration and configure the analogue outputs. Each gas concentration is further shown on a display on the maMoS gas monitor. The standard power supply is 24 VAC.

MaMoS-100
This instrument is a gas monitor for a single gas component. It can be equipped with one electrochemical or infrared sensor for semi-continuous monitoring of any of the gases measured with the portable instruments. Popular choices are methane (CH4) or carbon dioxide (CO2) for biogas or wastewater applications and carbon monoxide (CO) for combustion emission monitoring. Oxygen (O2) is also a popular choice in the packaging industry or food processing in general. Like all the maMoS series this can be fitted with a freely programmable relay output to switch a process according to a specific gas concentration. The instrument is fitted with linear current and voltage outputs in addition to a digital output that can either feed a computer display over the standard software or be used as part of a control system. This instrument provides a simple control module based on gas concentrations that will complement other industrial control systems.

MaMoS-200
The maMoS-200 is a gas monitor for two components that can be supplied with any combination of electrochemical or infrared sensors. There are separate current and voltage outputs for each of the channels, and these can also be configured independently to display the range of concentration that is of particular interest. The digital output brings the values from both sensors to a computer terminal where it can be stored or used for further control functions. The two gas models are commonly used for biogas systems, measuring oxygen (O2) and methane (CH4) or carbon dioxide (CO2) and methane. The oxygen measurement serves a safety function in that it can be used to prevent the formation of an explosive mixture. The presence of oxygen will also reduce or prevent the formation of methane, leading to increased carbon dioxide production.

MaMoS-300
Basically the same instrument as the smaller maMoS-100 and maMoS-200, this version has provision for up to three sensors. All the other options and standard features remain the same. This is commonly used for biogas applications where measurement of H2S is required or industrial pollution monitoring where simple gas measurements are the deciding factor independent of any calculated values. Many industries now require the addition of gases to systems, and the high cost of these gases makes monitoring the concentrations part of sensible business practice.

MaMoS-400
The maMoS-400 (picture not yet available) is simply a gas monitor with four channels available for gas measurement. This will enable the instrument to cover most pollution monitoring requirements as well as being used for industrial control applications. As with all the maMoS family, this monitor can be fitted with a relay output for each gas channel in addition to the standard analogue outputs for each component and the digital RS232C output. Picture not yet available

Common accessories
There are a number of common accessories that are regularly ordered with our instruments. This will give an overview of the most common ones and where they can be most easily used.

Minidryer

The minidryer is a common accessory to the GA-21plus and GA-40plus analysers. Theoretically, it can also be used with the GA-60, although there is no provision for attaching the minidryer in this instrument. The minidryer is supplied from the probe socket on the analyser. There is a simple switch to activate the minidryer, but it also detects activity from the analyser when it is switched on. The minidryer will cool the gases down to around +4°C or 12°C under ambient temperature, whichever is higher. The power requirement is around 12 W. The minidryer includes a peristaltic pump to remove the condensate quickly from the unit and reduce the contact time between the gases and water. This prevents the soluble gases being removed from the sample in solution. The minidryer requires an air supply for the cooling fan to operate, so this must not be blocked.

Alternative gas sensors

All of the larger instruments can be fitted with the infrared sensors for methane (CH4) and carbon dioxide (CO2). There is also the option to add low-range sensors for the other gases if this is required. This is particularly useful for ambient conditions or for traces of the gases. The low range allows a much higher resolution and an improved absolute accuracy of readings.

Probes
The probe is an integral necessity for a flue gas analyser. This does not apply in the same way to a gas monitor. The gas probe is available in a variety of lengths and temperature ranges. Probes are made in sizes of 150 mm, 300 mm, 450 mm, 750 mm, 1000 mm and 1500 mm for a maximum temperature of 800°C and 300 mm, 750 mm and 1500 mm for 1150°C. These have a NiCr-Ni thermocouple for temperature measurement integrated into the probe tip for measurement of the gas temperature. The probe comes with a conical fitting to fix it at the desired depth in the gas channel. Gas concentration and temperature measurements should be carried out at the hottest part of the gas flow; this is generally in the centre of the stack. This also means that the probe used should be at least half the diameter of the stack in length. There are also ceramic probes for temperatures up to 1600°C. These use a PtRh-Pt thermocouple. The ceramic probe is needed sometimes, such as in the glass industry, but should not be used unless genuinely needed. It is highly fragile and much more expensive to buy. The instrument must be set in the menu to use the PtRh-Pt thermocouple, otherwise the temperature display will be obviously incorrect. The probe will eventually corrode and fail in use, although this should take some time. The upper picture shows a selection of different lengths of probe and the lower picture shows a probe attached to the probe holder ready for use. The position of the cone is altered to suit the diameter of the flue gas channel. This will hold the probe in place and free up one hand for other activities.

Probe holder
The probe holder attaches to the probe mechanically and is also the electrical connection between the thermocouple and the analyser. The probe holder is a standard item that will fit all of the usual probes. The ceramic pro be requires a different probe holder, however. The probe holder comes in a range of types. For the GA-12 there is a simple unit combining probe and holder. A similar low-cost alternative is also available for the other analysers. The usual probe holder is a detachable unit that screws onto the probe and connects to the analyser with a 3 m tube and electrical cable. The probe holder is also used for the soot test. For this purpose a heated probe holder is needed, which has a slit to take the soot test paper. There is also an unheated, lower cost probe holder. The tubing from the probe holder is typically fitted with an inline filter and condensate trap. This may not be present if the analyser is fitted with its own filters on the inlet side. Some of the analysers have a different electrical connector for the probe holder, which means they are not easily interchangeable between models. The GA-12 and GA-12plus both have different connectors, whilst the GA-21plus, GA-40plus and GA-60 have the same connector. The GA-40Tplus has the heated hose as standard and therefore does not need the probe holder. Shown are a selection of probe holders, one with attached probe. The lower picture shows a heated probe holder with the filter paper for the soot test inserted in the slot ready for the test. The last picture shows the inline filter and condensate trap disassembled for changing the filter element. Care should be taken that the condensate trap part of the filter is indeed lower than the filter element in use, otherwise the unit will not function correctly. The transparent filter holder allows the condition of the filter to be monitored without disassembling the unit. The condensate trap should be emptied as needed and after the measurements in any case. This mixture of condensate, particulates and dissolved gases is mildly corrosive and will degrade the plastic of the condensate trap in time if left. The plastic filter insert can be dried if necessary. A wet filter will not let so much gas pass through.

Heated hose

The heated hose is used in all the gas analysers that have a gas cooler. The principle behind the heated hose is that it transfers the gas from the sampling point to the cooler of the analyser without allowing the gas temperature to drop below the dew point. This has a number of important reasons. Condensate formed will tend to dissolve the soluble gases such as NO2 and SO2 in the sample gas stream. This leads both to incorrect readings and also to the formation of corrosive acids that will attack the equipment. The present heated hoses are all fitted with a heated filter on the inlet side which will remove all larger particles from the gas and protect the system. The top picture shows the 3 metre heated hose for the GA-40Tplus. The centre picture shows the connection for the probe and the holder for the heated filter element. From the probe connection to the analyser the entire system is heated above the dew point of the gases, maintaining all the soluble gases in the vapour state and preventing formation of corrosive solution products in the gas tubing. The heated hose uses a Teflon tube for transport of the gases and this is very proof against chemical attack as well as being flexible. All parts that may come into contact with the gases are made of corrosion and heat resistant materials. The lower picture shows the magnetic connection that allows quick and simple assembly of the analysis system and it also shows the single electrical connection between heated hose and analyser. Although flexible, the heated hose should not be forced to make curves that do not occur naturally. The electrical wiring inside and the insulating material will fatigue in time if undue force is used, reducing the life of the hose unnecessarily. Especially the heated filter will become hot in use. Care should be taken when handling the hose for this reason. The hose should also be allowed to cool before being packed for transport to avoid damage to it and other articles it might come into contact with. In some applications, specifically with the GD-10 and PGD-100, the temperature of the hose can be regulated as required, but the GA-40Tplus runs the hose at a constant high temperature. This has no detrimental effect on measurements.
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