XRF 101: Choosing the Right Analyzer
Consider these seven points to help you identify what tool best meets your needs.
Before selecting an X-ray fluorescence (XRF) analyzer, consider what you want to achieve. For example, if you are looking to confirm alloy grades for incoming goods QC, you will want to know what the important element in those grades should be. In any manufacturing situation, verifying that you are using the correct specified alloy is critical.
Why use XRF?
Material mix-ups can be costly. XRF is a fast and nondestructive method for testing the composition of alloys and metals, as well as other materials. Handheld XRF analyzers have the flexibility to test and measure most alloy components with varying sizes and shapes, from metal turnings to strands of metal wire. However, handheld XRF cannot measure some elements like carbon or sodium. And XRF cannot tell you about the structure or physical integrity of what you are testing. There are other methods to test for those properties.
As a consumer, it can be difficult to understand the complexities surrounding the different X-ray fluorescence analyzers on the market, but considering these seven points will help you identify what tool best meets your needs.
Choosing the Right XRF Analyzer
1. Identify the materials you want to analyze
Identify what alloy grades or groups of alloys you want to analyze. Do you need to match a certain grade, or are you validating heat or batch chemistry?
2. Choose a detector type:
PIN or SDD
There are two types of detectors used in handheld XRF analyzers: PIN and SDD. PIN detectors are an older technology that is less expensive, but also less sensitive than a silicon drift detector (SDD). Your answers to the three questions below will help you determine whether or not you need the sensitivity of an SDD.
Do I need to measure light elements? In XRF lingo, light elements are magnesium, aluminum, silicon, phosphorous, and sulfur. If you need to know the concentration of these elements, then you need an SDD.
Is testing speed important? An SDD can identify most alloys in a second or two. A PIN instrument can take eight to 10 seconds to perform the same task. If you are testing many samples, the analysis time can add up, making the SDD instrument the cost-effective choice.
What is the lowest concentration level you need for each element? SDD instruments have lower limits of detection (LODs) than PIN instruments. Refer to the manufacturer’s LOD sheet, but understand that the reported LODs are typically under ideal conditions.
3. Select a detector size
If you have decided you need the throughput, sensitivity, and elemental range of the SDD, most manufacturers offer a standard SDD and a large area SDD. The large area SDD has better analytical sensitivity but costs more.
4. Choose an anode material
Some manufacturers carry a complete line of analyzers with a variety of available tube anode materials. Typical materials are rhodium (Rh), silver (Ag), and tungsten (W).
Rhodium: It is best for measuring light elements. It’s particularly fast at measuring magnesium, a key element in aluminum grades, making rhodium the best choice for most alloy applications.
Tungsten: The use of tungsten or a similar heavy material is best for high-energy elements like cadmium, which is important for RoHS testing.
Silver: A good all-around anode material, silver is not as good as rhodium for magnesium or tungsten for cadmium but is a good compromise anode.
Consult with the manufacturer for details and expert recommendations.
5. Select your options
Cameras: When documentation is important, purchase an analyzer with built-in cameras to document the sample tested and to position the instrument for testing.
Collimator: Some analyzers offer a collimator, which narrows the X-ray beam, so the spot size decreases from about 10 mm to 3 mm. This feature enables the inspector to select a small area for analysis, such as the weld seam in a pipe.
Connectivity features: Analyzers with Wi-Fi connectivity enable fast decision making in the field and easily accessible results. Direct export to a USB drive is a nice convenience on most modern analyzers.
6. Understanding the specifications for your environment
The instrument specifications that matter most when selecting an analyzer are the ones related to your environment. Think about where and how the analyzer will be used. Considerations include:
- IP rating: An IP rating means the analyzer is resistant to dust and water. This helps ensure your instrument can handle the rigors of rugged industrial environments.
- Drop tested: Tools sometimes get dropped or misplaced, but one drop shouldn’t put you out of business. Consider an instrument that has been drop tested to help prevent costly repairs.
- Operating temperature: When testing in hot environments, consider an instrument that can sustain all-day testing in hot environments.
7. Test it out
XRF analytical specifications can be confusing. People talk about count rate, resolution, voltage, and tube watts. While each of these can be important, what is most important is how they work together. It’s like buying a car—the compression ratio in the pistons doesn’t matter to most drivers. What matters is what happens when you step on the gas. So for XRF, pull the trigger and look at the results.
The only way to truly evaluate if an instrument is a good fit for your needs is to try it on your materials. Is it the right tool for what you are doing? Is the user interface responsive and easy to use and navigate? Clear, straightforward navigation is crucial for a good user experience and minimizing training. Is the information you need right there on the screen? Do you get lost setting up the analyzer? A good user experience translates to higher throughput and a faster return on investment.
After testing the instrument, you’ll be ready to get the right analysis tool in your toolbox and start saving time and money with your handheld XRF analyzer.