LGA-3500 FAQ​​

How flow sensitive if the LGA 3500 extractive unit?

For measuring water in chlorine, how does Chlorine butter affect the unit?

What values should be entered for purge and zero gas concentration?

What is the proper procedure for zeroing and spanning?

Can we zero in a vacuum?

For additional questions, please contact Technical Support​​.


Q: ​How flow sensitive if the LGA 3500 extractive unit?

A: The unit is not flow sensitive in normal use. Since you mentioned it is flow sensitive I would suggest you remove the Rota meter from the vent line, and vent to a constant pressure header. Pressure variations in the sample cell affect the reading on a one to one basis. Flow variations between 1SLPM to 3SLPM should cause less than 1% change in reading. ​

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Q: ​For measuring water in chlorine, how does Chlorine butter affect the unit?

A: Our expert is very familiar with Chlorine Butter build up, as we have done about 75 similar applications. For a laser unit such as this, it is the number two most done applications other than O2. Based on the previous experience with butter, we have found that it typically doesn’t give a problem in moderate amounts, as it is optically trans​missive in the wavelength of measurement. Only clean the cell when transmission drops under 30%.​

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Q: ​What values should be entered for purge and zero gas concentration?

A: Zero values must be entered for Zero Gas and for purge gas. Values other than zero are problematic from a software standpoint and must be avoided definitely. The reason they are adjustable in the SW is for the percent O2 application. For this application, however, giving non zero values can cause erratic behavior in the unit. ​

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Q: ​What is the proper procedure for zeroing and spanning?

A: For Zeroing and Spanning, the proper procedure is to introduce the gas and watch the display of the unit and wait for stability. Once the units reading has not changed for 15 minutes, one can call the reading stable and then go ahead and start pushing keys to initiate the calibration sequence. ​

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Q: ​Can we zero in a vacuum?

A: Zeroing in a vacuum is not recommended. The reason is that in a vacuum there is a narrowing of the absorption peak of the gas present, and this will cause an error. There is no mechanical risk to this, but there is the measurement error that will result. This is not recommend and we have no good results from anybody doing a zero cycle this way. ​

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