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英國SIGNAL氣體分析儀同其它分析儀的比較
點擊次數：4505 發布時間：2009-04-09
Application Notes 應用注解
Disadvantages of Ecophysics NOx analyser
1. Twin Reaction Chamber 雙反應室
There are several disadvantages in using a twin reaction chamber with one photo multiplier tube, for example:
采用帶光電倍增管的雙反應室存在以下幾個局限性，例如：
I. Reaction time and ‘PM’ tube offer little speed of response advantage over single reaction chamber and sample gas switching etc.
反應時間及光電倍增管提供有限的響應速度較之單一反應室及樣氣轉換沒有明顯優勢。
II. The arrangement requires a motor driven shutter to alternate each reaction chamber to ‘PM’ Tube.
要求馬達驅動斬波器去交替每個反應室到光電倍增管。
2. Ozonizer臭氧發生器
Double the level of ozone is needed （enough for reaction chambers）. This necessitates the use of a high strength corona discharge method. With this strength N2 in the air feed gas produces:
要供足每個反應室需要雙倍的臭氧，因此必須使用高能量的電暈放電方法，在這種能量下空氣中的原料氣會產生N2。
I. NO gas at around 2 ppm and this produces an offset seen as non-linearity at lower ranges.
NO氣體大約2 ppm，在低量程時會產生非線性漂移。
II. Any moisture in the air feed gas quickly produces Nitric Acid, which corrodes and blocks the ozone supply.
空氣中任何濕氣進入會快速生成硝酸，將腐蝕及阻塞臭氧的供應。
III. A large capacity ozone scrubber is required to remove prior to the Vac pump.
要求大容量的臭氧去除器預先去除真空泵上的臭氧。
3. NOx Converter NOx轉化爐
The welded construction converter produces a considerable restriction, which acts as a filter. This leads to a difference in the amount of impurities each of the two reaction chamber receive i.e. the NOx channel receive less due to filtration by the NOx converter than the NO channel, this leads to an offset between NOx and NO channels producing an error in the NO2 reading that the single reaction chamber does not.
焊接結構的轉換爐受太多的條件限制，作為過濾器，將導致兩個反應氣室的雜質總量不一樣，即：由于NOX通道由于經過NOX 轉化爐過濾，進入的雜質將比NO通道少，因此產生一個偏移，導致NOX 通道與NO通道之間產生一個有誤差的NO2讀數，單一反應室則沒有這種情況。
The NOx converter is not designed for low cost maintenance and is an exchange item.
這種NOx轉換爐維護保養成本過高。
The stainless steel material is able to convert ammonia to NO and produces unwanted readings.
不銹鋼材料會將氨轉換為NO，導致NO讀數偏高
The stainless steel converter diminishes NO to N2 in a low oxygen sample gas.
不銹鋼材料轉化爐在樣氣低氧的情況下，NO會減少轉變為N2
The normally used carbon converter does not have a filteration effect. It does not produce NO from ammonia and does not have the effect reducing NO to N2 in a reducing atmosphere sample. It is also easy and cheap to replenish.
通常使用碳轉化爐不會有過濾效應，它不會使氨轉變為NO，在樣氣有還原氛時也不還原NO成N2，并且容易更換、費用低廉。
4. Oven爐
The Ecophysics unit has an internal sample filter, which can only be accessed, through a hole in the back panel. The solenoid valve in the oven to select CAL gas or SAMPLE gas is very expensive to overhaul and/or replace.
Eco 內置樣氣過濾單元，僅被設計通過一個孔進入后背板，爐內的用于選擇校準氣或樣氣的電磁閥在檢查及更換時費用昂貴。
5. Vacuum Regulator真空調節器
Instead of using a high quality mechanical vacuum regulator, Ecophysics use an electronic vacuum transducer to monitor the vacuum and operates a motor driven toothed rubber belt, which operates a needle valve within an electronic feedback circuit.
This is very expensive, quite unnecessary and expensive to maintain. The toothed belt require frequent replacement as ozone leakage even on a small scale destroys the rubber. The motor requires maintenance and the electronic transducers is expensive to replace.
與SIGNAL采用高品質的機械真空調節器不一樣，Eco卻使用了一個電子真空變頻器來監控真空度及通過電機驅動齒形橡膠傳動帶，開動電子反饋電路里的針形閥。這非常昂貴并且沒必要，而且維護費用特別昂貴。由于臭氧泄漏會導致橡皮損壞，以致齒形傳動帶需要頻繁的更換。電機需要維護保養，并且電子變頻器更換起來費用也很昂貴。
The Signal Model 4000VM uses a high quality mechanical regulator which require only the replacement if the diaphragm from time to time.
Signal Model 4000VM使用了高品質的機械式真空調節器，有時僅僅需要更換膜片。
6. Vacuum Pump真空泵
The chemiluminescent NOx analyser has greatly improved sensitivity and low quenching from CO2 and H2O when under high vacuum.
NOx化學發光分析儀的靈敏度已經有極大的改善并且在高真空狀態下將CO2和H2O淬火影響降到低。
The Ecophysics dual reaction chamber unit has two reaction chamber flows of sample and ozone. The vacuum pump has twice the flow rate and therefore pulls much less vacuum.
Eco 雙反應室單元有兩個反應室流動樣氣與臭氧。因此要求真空泵需要雙倍的流速來適應更少的真空度
The Signal unit pulls down to 15mbar vacuum.
Signal單元真空度達到到15mba
The Signal Model 4000VM is able to offer continuous NOx/NO/NO2 output. Updated every 3 seconds which is equivalent to Ecophysics twin reaction chamber design.
It has a ‘soft’ neon tube ozoniser which does not produce NO fro air feed gas and therefore does not suffer from nitric acid production if the air feed gas is not totally dry and it does not produce an error in the NO2 reading due to a difference in window contamination due to the filtering effect of the NOx converter.
Signal Model 4000VM 提供NOx/NO/NO2 連續輸出，每3秒鐘刷新一次數據，等同于ECO雙反應室設計，它有一個氖管臭氧發生器，不會經由空氣原料氣生成NO，因此當空氣原料氣不*干燥的情況下也不用擔心產生硝酸，由于NOX轉化爐產生過濾效應但污染物是在不同的窗口，所以NO2的讀數不會出現誤差。
The ozoniser does not produce so much ozone that it needs an electrical ozone destroyer and does not produce NO from air feed gas that will produce a low-level range non-linearity.
此臭氧發生器不會產生太多的臭氧，它需要一個電子臭氧破壞器，不會從空氣原料氣中生成NO而產生低量程時的非線性
The carbon converter is situated in a quartz chamber that does not convert ammonia and will not reduce NO to N2, it is also easy and cheap to refill.
碳轉化爐安放在一個石英室內，它不會轉化氨，NO也不會被還原為N2, 更換方便而且價格經濟
The vacuum regulator is the high quality mechanical type that requires little or no maintenance but still offers the same performance in sample bypass effects as that of the Ecophysics.
它的真空調節器是高品質機械型的，幾乎不需要維護與保養，但仍然提供與Eco在樣本氣體旁路作用方面一樣的性能
The sample oven is fitted with Teflon filter removable from the rear and it uses a regulator solenoid valve for sample/Cal gas section which has its solenoid coil external to the heated area in order to provide reliable long term use. It is also low cost to maintain.
樣品爐后面安置了一個抽取式的聚四氟乙烯過濾器，用一個調壓電磁閥控制樣氣及校準氣，為了安全可靠使用，外部纏繞螺旋加圈，維護與保養的成本也很低。
Summary總括
The Ecophysics analyser is a remarkable design for complexity over simplicity. The complexity offers no performance advantage but many cost and maintenance disadvantages.
The Ecophysics analyser also incorporates design that have series disadvantages in error in readings.
Eco分析儀在設計上很明顯過于復雜化，此種復雜的設計除了帶來更高的維護成本及維護方面的劣勢外，在性能上并沒有任何優勢。
Eco分析儀的總體設計有一系列導致讀數錯誤的劣勢
a） Different contamination in NOx/NO channels
在NOx與NO通道上有不同程度的污染
b） Ammonia effects with converter
氨會對轉化爐產生影響
c） Loss of NO to N2 in converter.
轉化爐內NO還原成N2
d） Nitric oxide production in ozoniser if an air feed gas is not totally dry.
