![]() The beta ratio at a certain micron size is simply the ratio of the number of particles upstream of the filter at a given size range versus downstream. The test, which is covered under the ISO 16889 standard, uses a multi-pass test stand to empirically determine the capture efficiency of a filter at specific micron sizes (Figure 1). The beta rating of a filter is measured by comparing the number of particles upstream and downstream of a filter at a given micron size.īeta efficiency: The beta rating of a filter is a measure of the expected capture efficiency at a given micron size. While there are engineering standards that are used to define a filter’s absolute rating, in practice most absolute-rated oil filters have a capture efficiency of 97% to 98% at the stated micron rating. Since the pore sizes of any oil filter are not uniform throughout the filter, in practice, absolute oil filters rarely if ever perform at 100% capture efficiency for their absolute micron rating. Unfortunately, nominally rated filters are often used because they are typically the least expensive.Ībsolute efficiency: The term absolute might suggest that a specific filter “absolutely” removes all particles greater than a certain size rating. When evaluated with more rigorous efficiency testing, such as the multi-pass beta rating test (see below), nominally rated filters often have less than a 50% capture efficiency at the stated micron size, e.g., a 10-micron nominal filter only has a one in two chance of capturing 10-micron particles. A nominal filter rating is little more than an estimate by the manufacturer of the filter’s true capture efficiency. ![]() Nominal efficiency: The nominal efficiency of a filter does not have any engineering definition. The micron rating of a filter is nothing more than an extension of the part number code based on one of three measurements of filtration efficiency: nominal, absolute, and beta. However, this is where things are not always as they should be. See Adding Prompts for more details.įilters correspond to the WHERE clauses in SQL, and are used to specify that only certain rows of a table shall be retrieved from the data source, based on the criteria described in the filtering condition.įilter elements can be applied as required by the person creating information links.The micron rating is a measure of the size of particles the filter might be expected to capture. For each column that has been set up like this, a dialog will appear allowing the user to enter threshold values or select individual values. However, the actual conditions are entered by the person running the information link only when the link is opened (executed). Prompts are also set up when you create an information link. ![]() See Adding Hard Filters for more details. Also, hard filters can only specify a range or a list of values, and so are less versatile than filter elements. This means that they cannot be reused in other links. Hard filters are set up as you define the information link, and are saved with the link. See Creating an information link to find out how to include a filter element. They can be added to any information link, just like column elements. ![]() There are three ways of filtering data when working with information links:įilter elements appear in the Elements tree of Information Designer. For example, a filter could set the conditions "X > 10 AND Y < 100". Filter Elements Overview Filter Elements Overviewįilters are conditions that limit the amount of data returned by an information link. ![]()
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