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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(shù)：5811 發(fā)布時間：2009-04-09
Application Notes 應(yīng)用注解
Disadvantages of Ecophysics NOx analyser
1. Twin Reaction Chamber 雙反應(yīng)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(yīng)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(yīng)時間及光電倍增管提供有限的響應(yīng)速度較之單一反應(yīng)室及樣氣轉(zhuǎn)換沒有明顯優(yōu)勢。
II. The arrangement requires a motor driven shutter to alternate each reaction chamber to ‘PM’ Tube.
要求馬達(dá)驅(qū)動斬波器去交替每個反應(yīng)室到光電倍增管。
2. Ozonizer臭氧發(fā)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(yīng)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(chǎn)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(chǎn)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(jìn)入會快速生成硝酸，將腐蝕及阻塞臭氧的供應(yīng)。
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(yù)先去除真空泵上的臭氧。
3. NOx Converter NOx轉(zhuǎn)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(jié)構(gòu)的轉(zhuǎn)換爐受太多的條件限制，作為過濾器，將導(dǎo)致兩個反應(yīng)氣室的雜質(zhì)總量不一樣，即：由于NOX通道由于經(jīng)過NOX 轉(zhuǎn)化爐過濾，進(jìn)入的雜質(zhì)將比NO通道少，因此產(chǎn)生一個偏移，導(dǎo)致NOX 通道與NO通道之間產(chǎn)生一個有誤差的NO2讀數(shù)，單一反應(yīng)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(zhuǎn)換爐維護(hù)保養(yǎng)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(zhuǎn)換為NO，導(dǎo)致NO讀數(shù)偏高
The stainless steel converter diminishes NO to N2 in a low oxygen sample gas.
不銹鋼材料轉(zhuǎn)化爐在樣氣低氧的情況下，NO會減少轉(zhuǎn)變?yōu)?/span>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(zhuǎn)化爐不會有過濾效應(yīng)，它不會使氨轉(zhuǎn)變?yōu)?/span>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(nèi)置樣氣過濾單元，僅被設(shè)計通過一個孔進(jìn)入后背板，爐內(nèi)的用于選擇校準(zhǔn)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(diào)節(jié)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(zhì)的機(jī)械真空調(diào)節(jié)器不一樣，Eco卻使用了一個電子真空變頻器來監(jiān)控真空度及通過電機(jī)驅(qū)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(hù)費用特別昂貴。由于臭氧泄漏會導(dǎo)致橡皮損壞，以致齒形傳動帶需要頻繁的更換。電機(jī)需要維護(hù)保養(yǎng)，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(zhì)的機(jī)械式真空調(diào)節(jié)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(xué)發(fā)光分析儀的靈敏度已經(jīng)有極大的改善并且在高真空狀態(tài)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(yīng)室單元有兩個反應(yīng)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(yīng)更少的真空度
The Signal unit pulls down to 15mbar vacuum.
Signal單元真空度達(dá)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(xù)輸出，每3秒鐘刷新一次數(shù)據(jù)，等同于ECO雙反應(yīng)室設(shè)計，它有一個氖管臭氧發(fā)生器，不會經(jīng)由空氣原料氣生成NO，因此當(dāng)空氣原料氣不*干燥的情況下也不用擔(dān)心產(chǎn)生硝酸，由于NOX轉(zhuǎn)化爐產(chǎn)生過濾效應(yīng)但污染物是在不同的窗口，所以NO2的讀數(shù)不會出現(xiàn)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(fā)生器不會產(chǎn)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(chǎn)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(zhuǎn)化爐安放在一個石英室內(nèi)，它不會轉(zhuǎn)化氨，NO也不會被還原為N2, 更換方便而且價格經(jīng)濟(jì)
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(diào)節(jié)器是高品質(zhì)機(jī)械型的，幾乎不需要維護(hù)與保養(yǎng)，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(diào)壓電磁閥控制樣氣及校準(zhǔn)氣，為了安全可靠使用，外部纏繞螺旋加圈，維護(hù)與保養(yǎng)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(shè)計上很明顯過于復(fù)雜化，此種復(fù)雜的設(shè)計除了帶來更高的維護(hù)成本及維護(hù)方面的劣勢外，在性能上并沒有任何優(yōu)勢。
Eco分析儀的總體設(shè)計有一系列導(dǎo)致讀數(shù)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(zhuǎn)化爐產(chǎn)生影響
c） Loss of NO to N2 in converter.
轉(zhuǎn)化爐內(nèi)NO還原成N2
d） Nitric oxide production in ozoniser if an air feed gas is not totally dry.
