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英国SIGNAL气体分析仪同其它分析仪的比较
点击次数：4191 发布时间：2009-04-09
Application Notes 应用注解
Disadvantages of Ecophysics NOx analyser
1. Twin Reaction Chamber 双反应室
There are several disadvantages in using a twin reaction chamber with one photo multiplier tube, for example:
采用带光电倍增管的双反应室存在以下几个局限性，例如：
I. Reaction time and ‘PM’ tube offer little speed of response advantage over single reaction chamber and sample gas switching etc.
反应时间及光电倍增管提供有限的响应速度较之单一反应室及样气转换没有明显优势。
II. The arrangement requires a motor driven shutter to alternate each reaction chamber to ‘PM’ Tube.
要求马达驱动斩波器去交替每个反应室到光电倍增管。
2. Ozonizer臭氧发生器
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:
要供足每个反应室需要双倍的臭氧，因此必须使用高能量的电晕放电方法，在这种能量下空气中的原料气会产生N2。
I. NO gas at around 2 ppm and this produces an offset seen as non-linearity at lower ranges.
NO气体大约2 ppm，在低量程时会产生非线性漂移。
II. Any moisture in the air feed gas quickly produces Nitric Acid, which corrodes and blocks the ozone supply.
空气中任何湿气进入会快速生成硝酸，将腐蚀及阻塞臭氧的供应。
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预先去除真空泵上的臭氧。
3. NOx Converter NOx转化炉
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.
焊接结构的转换炉受太多的条件限制，作为过滤器，将导致两个反应气室的杂质总量不一样，即：由于NOX通道由于经过NOX 转化炉过滤，进入的杂质将比NO通道少，因此产生一个偏移，导致NOX 通道与NO通道之间产生一个有误差的NO2读数，单一反应室则没有这种情况。
The NOx converter is not designed for low cost maintenance and is an exchange item.
这种NOx转换炉维护保养成本过高。
The stainless steel material is able to convert ammonia to NO and produces unwanted readings.
不锈钢材料会将氨转换为NO，导致NO读数偏高
The stainless steel converter diminishes NO to N2 in a low oxygen sample gas.
不锈钢材料转化炉在样气低氧的情况下，NO会减少转变为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.
通常使用碳转化炉不会有过滤效应，它不会使氨转变为NO，在样气有还原氛时也不还原NO成N2，并且容易更换、费用低廉。
4. Oven炉
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 内置样气过滤单元，仅被设计通过一个孔进入后背板，炉内的用于选择校准气或样气的电磁阀在检查及更换时费用昂贵。
5. Vacuum Regulator真空调节器
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.
与SIGNAL采用高品质的机械真空调节器不一样，Eco却使用了一个电子真空变频器来监控真空度及通过电机驱动齿形橡胶传动带，开动电子反馈电路里的针形阀。这非常昂贵并且没必要，而且维护费用特别昂贵。由于臭氧泄漏会导致橡皮损坏，以致齿形传动带需要频繁的更换。电机需要维护保养，并且电子变频器更换起来费用也很昂贵。
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使用了高品质的机械式真空调节器，有时仅仅需要更换膜片。
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化学发光分析仪的灵敏度已经有极大的改善并且在高真空状态下将CO2和H2O淬火影响降到低。
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 双反应室单元有两个反应室流动样气与臭氧。因此要求真空泵需要双倍的流速来适应更少的真空度
The Signal unit pulls down to 15mbar vacuum.
Signal单元真空度达到到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 连续输出，每3秒钟刷新一次数据，等同于ECO双反应室设计，它有一个氖管臭氧发生器，不会经由空气原料气生成NO，因此当空气原料气不*干燥的情况下也不用担心产生硝酸，由于NOX转化炉产生过滤效应但污染物是在不同的窗口，所以NO2的读数不会出现误差。
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.
此臭氧发生器不会产生太多的臭氧，它需要一个电子臭氧破坏器，不会从空气原料气中生成NO而产生低量程时的非线性
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.
碳转化炉安放在一个石英室内，它不会转化氨，NO也不会被还原为N2, 更换方便而且价格经济
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.
它的真空调节器是高品质机械型的，几乎不需要维护与保养，但仍然提供与Eco在样本气体旁路作用方面一样的性能
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.
样品炉后面安置了一个抽取式的聚四氟乙烯过滤器，用一个调压电磁阀控制样气及校准气，为了安全可靠使用，外部缠绕螺旋加圈，维护与保养的成本也很低。
Summary总括
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分析仪在设计上很明显过于复杂化，此种复杂的设计除了带来更高的维护成本及维护方面的劣势外，在性能上并没有任何优势。
Eco分析仪的总体设计有一系列导致读数错误的劣势
a） Different contamination in NOx/NO channels
在NOx与NO通道上有不同程度的污染
b） Ammonia effects with converter
氨会对转化炉产生影响
c） Loss of NO to N2 in converter.
转化炉内NO还原成N2
d） Nitric oxide production in ozoniser if an air feed gas is not totally dry.
