Diagnostic testing methods for spectrometers

Abstract

A diagnostic testing method for a detector in a spectrometer is provided. The spectrometer includes a line spectral source configured to emit at least one branched spectral line pair from an excited species. The diagnostic testing method includes performing multiple detector diagnostic measurements and diagnosing the operational status of the detectors. Each detector diagnostic measurement includes: measuring the intensity of a first spectral line emitted by the excited species from the line spectral source using a detector; and measuring the intensity of a second spectral line emitted by the excited species from the line spectral source using a detector. The first and second spectral lines emitted by the excited species from the line spectral source form a branched spectral line pair, and for the multiple detector diagnostic measurements, the spectrometer is controlled to vary the intensities of the first and second spectral lines incident on the detector. For each of the multiple detector diagnostic measurements, the operational status of the detector is diagnosed based on the ratio of the intensity of the first spectral line to the intensity of the second spectral line.

Description

Technical Field

[0001] This disclosure relates to a spectrometer. Specifically, this disclosure relates to a spectrometer that includes a plasma light source. Background Technology

[0002] The operation of analytical instruments such as spectrometers involves interactions between many advanced assemblies (HLAs). To ensure the smooth operation of analytical instruments, it is beneficial to identify when the operation of HLAs deviates from their expected behavior. It may also be beneficial to identify whether a particular HLA is operating as expected so that it can be ruled out from further troubleshooting steps. Furthermore, early detection of HLAs exhibiting deviant behavior allows for the implementation of predictive maintenance.

[0003] In sequential analytical plasma spectrometers, one such HLA component is a single-channel detector such as a photomultiplier tube (PMT), while in simultaneous analytical plasma spectrometers, a such HLA component is a multi-channel detector such as a charge-coupled device (CCD), complementary metal-oxide-semiconductor (CMOS) detector, or charge injection device (CID) detector camera. To examine the behavior of single-channel or multi-channel detectors, individual light sources with known wide wavelength spectra and tunable radiant flux can be used. Mercury pen lamps, deuterium lamps, or tungsten lamps are commonly used for this purpose.

[0004] To examine the detector's behavior, a separate light source can be mounted to the spectrometer and adjusted. Alternatively, the detector can be removed from the spectrometer and tested on a test bench equipped with a stable light source. Therefore, testing the detector with a light source involves some degree of manual assembly / disassembly of the spectrometer.

[0005] Furthermore, it is known that the light source used for testing degrades over time. Therefore, the light source must be recalibrated periodically to maintain the known wide wavelength spectrum.

[0006] Another known method for examining the behavior of an analytical plasma spectrometer detector is to nebulize a series of standard solutions of known concentrations into the plasma and measure the analytical signal generated by the standard species. Standard solutions of varying concentrations can be prepared and nebulized into the plasma to produce different concentrations of analyte atoms within the plasma observation region, resulting in different light intensities at the detector. The preparation and maintenance of standard solutions are very time-consuming because the concentration of the solution may change over time as it ages. Changing the concentration level of the solution requires user intervention or the use of an autosampler. Methods based on standard solutions are known to be prone to dilution errors. Furthermore, changes in the solution flow rate, nebulization efficiency, and temperature within the source when the standard solution concentration changes will cause nonlinearities in the concentration dependence of the measured signal. Such source-derived nonlinearities may lead to erroneous conclusions that the detector response is nonlinear.

[0007] In addition to the aforementioned sources of nonlinearity, another source of nonlinearity is the self-absorption of light by a species in a steady state (i.e., unexcited) or metastable state (excited but with a long lifetime), when the species absorbs a portion of the light emitted by the same species in a (more)excited state (e.g., at a higher energy level).

[0008] Even with a perfectly functioning detector, the accuracy of both standard solution-based and external light source methods is limited by the random noise generated by the light source. This random noise is present in every measurement performed by the detector and typically constitutes at most a few percent of the signal. The main components of the source noise are shot noise and flicker noise.

[0009] One known type of spectrometer is the analytical plasma spectrometer. Such spectrometers can use inductively coupled plasma (ICP), laser-induced plasma (LIP), microwave-induced plasma (MIP), electric arc, or spark discharge as sources of light radiation. Light radiation from ICP and LIP sources has been used to determine the spectral responses of the following spectrometers: PSDoidge et al., *Acta Spectrochimica Sinica*, 1999, B54, 2167-2182; and X. Li, BWSmith, N. Omenetto, *Journal of Analytical Atomic Spectroscopy*, 2014, 29, 657-664. In these papers, the intensities of spectral line pairs originating from the same plasma gas or analyte element at the same high energy level were measured. The relative intensities of these spectral line pairs were calculated together with the known branching ratios of the spectral line pairs to calculate the spectral response curve of the spectrometer. Spectral line pairs with overlapping wavelengths over a wide wavelength range were measured to construct the spectral response curve of the system over a broad wavelength range.

[0010] The purpose of this disclosure is to provide an improved diagnostic testing method for detectors from spectrometer sources, which addresses or at least provides a commercially useful alternative to at least one or more problems associated with prior art methods. Summary of the Invention

[0011] As explained in this disclosure, the intensity relationship between branches of spectral lines emitted by a species from a suitable line spectral source can be used to perform diagnostic tests on the detector of a spectrometer that includes the line spectral source.

[0012] According to a first aspect of this disclosure, a diagnostic testing method is provided for a detector of a spectrometer including a line spectral source. The line spectral source may be configured to emit at least one pair of branched spectral lines from an excited species. The diagnostic testing method includes:

[0013] Perform multiple detector diagnostic measurements; each detector diagnostic measurement includes:

[0014] The detector is used to measure the intensity of the first spectral line emitted by the excited species from the line spectral source; and

[0015] The detector is used to measure the intensity of the second spectral line emitted by the excited species from the line spectral source;

[0016] The first spectral line and the second spectral line emitted by the excited species of the line spectral source form a branched spectral line pair;

[0017] For diagnostic measurements of the plurality of detectors, the spectrometer is controlled to change the intensity of the first and second spectral lines incident on the detectors; and

[0018] For each of the plurality of detector diagnostic measurements, the operational status of the detector is diagnosed based on the ratio of the intensity of the first spectral line to the intensity of the second spectral line.

[0019] Advantageously, the method according to the first aspect utilizes the line spectral source of the spectrometer as part of the diagnostic testing method for the spectrometer detector. The method according to the first aspect does not require an external light source and does not require removing the line spectral source or detector from the spectrometer to perform the diagnostic testing method. Instead, the operational status of the spectrometer detector can be diagnosed in situ using the line spectral source of the spectrometer. By diagnosing the operational status of the detector in situ, the diagnostic testing method can quickly and effectively identify whether the detector (HLA part) is behaving as expected or whether further investigation of the detector is required. Therefore, the diagnostic testing method can improve the fault diagnosis or maintenance process of the spectrometer.

[0020] The diagnostic method of the first aspect of the present invention utilizes spectral lines emitted by an excited species from a line spectral source (e.g., argon from an ICP source). Therefore, the diagnostic test method according to the first aspect can also be performed without using a standard solution to provide the excited species. Using spectral emission from a line spectral source avoids any measurement uncertainties that may be associated with dilution or aging changes of the standard solution. Thus, the method of the first aspect provides a diagnostic test method with improved efficiency and accuracy.

[0021] The diagnostic testing method of the first aspect utilizes the intensity relationship between branched spectral line pairs. This relationship is independent of the conditions within the line spectral source and the concentration of associated species in the line spectral source. Therefore, the diagnostic testing method according to the first aspect can be performed with improved accuracy. Furthermore, since the diagnostic testing method may not require any further adjustments to the spectrometer, it can be easily integrated into fully or partially automated spectrometer diagnostic workflows.

[0022] In some embodiments, the excitation species is provided by one or more of a standard solution atomized into the plasma at a known concentration or a plasma gas species. In some embodiments where the excitation species is provided by a standard solution, the diagnostic method can be performed multiple times, each time using a standard solution with a different known concentration. Therefore, the diagnostic test method may include the generation of concentration profiles to further improve the accuracy of the diagnostic test method.

[0023] In some embodiments, for diagnostic measurements of the plurality of detectors, at least one of the following is controlled: the line spectral source, the detector, and one or more optical elements between the line spectral source and the detector, to change the intensity of the first spectral line and the second spectral line incident on the detector. By controlling the spectrometer to change the intensity of the spectral lines, the diagnostic testing method can be easily implemented as an automated testing process.

[0024] A line spectral source is understood to provide a source of electromagnetic radiation. Electromagnetic radiation (e.g., light) is emitted by excited species of the line spectral source. A line spectral source may include one or more excited species. It should be understood that excited species are those that are excited to higher energy states. When a species transitions from a higher energy state to a lower energy state, electromagnetic radiation is emitted as spectral lines. When a species transitions from the same higher energy state to a different lower energy state, a pair of branched spectral lines is formed. Therefore, it should be understood that light emitted by a line spectral source has at least one pair of spectral lines (a first spectral line and a second spectral line) produced by radiative transitions from the same higher energy state to different lower energy levels.

[0025] In some embodiments, the line spectral source is a plasma source. For example, the plasma source may be an inductively coupled plasma (ICP) source, a laser-induced plasma (LIP), a microwave-induced plasma (MIP), an arc or spark discharge, or any other plasma source. In some embodiments, the line spectral source may be a flame or a furnace. In some embodiments, the excitation species is provided by a standard solution having a known concentration nebulized into the plasma source.

[0026] In some embodiments where the online spectral source is a plasma source, controlling the plasma source to change the intensity of the first and second spectral lines includes controlling one or more of the following: auxiliary gas flow rate, nebulizer gas flow rate, and cooling gas flow rate. The spectrometer may include one or more mass flow controllers for controlling the auxiliary gas flow rate, nebulizer gas flow rate, and / or cooling gas flow rate. Therefore, diagnostic testing methods can be economically implemented on the spectrometer without additional control components.

[0027] In some embodiments, if a synchronous spectrometer is used, the intensity measurement of the first spectral line is performed simultaneously with the intensity measurement of the second spectral line. By simultaneously measuring the first and second spectral lines, the flicker noise present in the measurement of the first spectral line will be correlated with the flicker noise present in the measurement of the second spectral line. Since the determination is based on the ratio of the two measurements, the flicker noise can be reduced or eliminated from subsequent determinations of the detector's operating condition. By eliminating flicker noise, the detector's operating condition can be diagnosed with very high accuracy.

[0028] In some embodiments, the diagnostic testing method further includes performing further multiple detector diagnostic measurements using different branched spectral line pairs emitted by the excitation species of the line spectral source. The different branched spectral line pairs can be emitted by the same excitation species of the line spectral source or by different excitation species of the line spectral source. The determination of the detector's operating condition can then take into account the ratio of the intensities of the different branched spectral line pairs in each of the additional multiple detector diagnostic measurements. Therefore, the diagnostic testing method can be repeated using multiple branched spectral line pairs emitted by the line spectral source. By using multiple branched spectral line pairs, the operating range and accuracy of the diagnostic testing method can be further improved.

[0029] In some embodiments, the diagnostic testing method can be used to diagnose different regions of the detector. Therefore, the diagnostic testing method of the first aspect can be repeated, wherein different regions of the detector are illuminated by a line spectral source. In some embodiments that measure multiple branched spectral line pairs, different branched spectral line pairs can be used to test different regions of the detector. In some embodiments, one or more optical elements between the detector and the line spectral source can be used to guide the spectral lines to different regions of the detector. In some embodiments, at least one of the optical elements can be a dispersive optical element. Therefore, the diagnostic testing method can be used to determine the operating condition of a specific region of the detector. Therefore, the diagnostic testing method can be used to determine whether there are any changes in the operating condition of the detector in the detector region.

[0030] In some embodiments, the diagnosed operating condition of the detector includes a normal operating condition or an abnormal operating condition. By normal operating condition, it should be understood that the detector's response to spectral lines of varying intensities is sufficiently linear for the purpose of the experiment to be performed on the spectrometer. Those skilled in the art will understand that the response of a detector operating under normal operating conditions may not be perfectly linear due to anticipated experimental noise. Therefore, the normal operating condition of the detector can have a substantially linear response (i.e., within a narrow range considered linear). In some embodiments, the range considered linear (i.e., the range of normal operation) can be specified by the user as an input parameter for the diagnostic test method.

[0031] Abnormal operating conditions indicate that the detector's response is not functioning as expected. In some embodiments, abnormal operating conditions may include nonlinear operating conditions and excessive noise operating conditions. Therefore, diagnostic testing methods can classify abnormal operating conditions as either nonlinear operating conditions or excessive noise operating conditions (or any other operating conditions). Thus, in the event of a diagnosed abnormal operating condition, the method may further include, for each of the plurality of detector diagnostic measurements, diagnosing the nonlinear operating condition or excessive noise operating condition based on the ratio of the intensity of the first spectral line to the intensity of the second spectral line.

[0032] Under nonlinear operating conditions, the diagnostic method systematically diagnoses a deviation of the ratio from the expected linear behavior. It should be understood that the detector's response to spectral lines of varying intensities is nonlinear, which can negatively impact the accuracy of experiments to be performed on the spectrometer. Therefore, the identification of nonlinear operating conditions can be an indication of a detector malfunction that may require further investigation.

[0033] In excessively noisy operating conditions, the ratio of each diagnostic measurement fluctuates excessively and randomly around the expected linear relationship.

[0034] In some embodiments, diagnosing the normal operating condition of the detectors includes determining, for each of the plurality of detector diagnostic measurements, that the ratio of the intensity of the first spectral line to the intensity of the second spectral line forms a linear relationship. For example, a linear relationship can be determined when each of the ratios determined for the plurality of detector diagnostic measurements falls within a predetermined range. In some embodiments, a normal operating condition can be determined where the intensity ratio of the first spectral line to the second spectral line is substantially constant for the plurality of detector diagnostic measurements. By being substantially constant, the method can diagnose the normal operating condition based on the residual standard deviation of the intensity ratios of the plurality of detector diagnostic measurements.

[0035] In some embodiments, if an abnormal (or nonlinear) operating condition is diagnosed, the diagnostic testing method further includes determining whether a first spectral line and / or a second spectral line forming a branched spectral line pair undergoes self-absorption. Self-absorption occurs when the light of the first spectral line and / or the second spectral line interacts with the same species of the line spectral source, thereby reducing the intensity of the corresponding spectral line relative to the expected value (based on transition probabilities). The diagnostic testing method may also perform checks to see if the identified abnormal (or nonlinear) operating condition can be explained by self-absorption rather than by the operating condition of the detector.

[0036] In some embodiments, if self-absorption is determined in the first spectral line and / or the second spectral line, the diagnostic method can be repeated using additional branched spectral line pairs with different wavelengths. Therefore, the diagnostic testing method can detect and self-correct any self-absorption that may exist in the line spectral source.

[0037] In some embodiments, if an abnormal operating condition is diagnosed, the diagnostic testing method further includes determining whether the measurement of the first spectral line and / or the measurement of the second spectral line has experienced line positioning error. Line positioning error occurs when the position of the first spectral line and / or the second spectral line incident on the detector deviates from their expected position. Line positioning error may be caused by temperature variations in one or more optical elements, as well as source spectral line shift and broadening. This error can be significantly reduced by increasing the spectral line profile portion generated for the measured signal and by performing all measurements over a short period of time. By checking to see if line positioning error still occurs, the diagnostic testing method can have even improved reliability.

[0038] In some embodiments, if a line positioning error is determined to have occurred, the spectrometer is adjusted to reduce the line positioning error. After adjustment, multiple detector diagnostic measurements can be repeated. By repeating the measurements after adjustment, the accuracy of the detector diagnostic measurements can be improved. In some embodiments, the measurements of the first and second spectral lines can be recalibrated to address the line positioning error, wherein for each of the multiple detector diagnostic measurements, the operating condition of the detector is determined based on the ratio of the recalibrated intensity of the first spectral line to the recalibrated intensity of the second spectral line. Therefore, in some embodiments, the spectrometer can account for the line positioning error without repeating the measurements. Such features allow for relatively rapid diagnostic testing methods.

[0039] In some embodiments, the diagnostic testing method is performed on one or more of the following: a photomultiplier tube detector, a charge-coupled device (CCD) detector, a complementary metal-oxide-semiconductor (CMOS) detector, and a charge injection device (CID) detector. Therefore, the diagnostic testing method can be performed on a variety of spectrometers incorporating multiple detectors.

[0040] According to a second aspect of this disclosure, a method for optical emission spectroscopy of a spectrometer is provided. The spectrometer includes a plasma source and a detector. The method of the second aspect includes performing a diagnostic test method according to the first aspect of this disclosure. For example, according to the second aspect, the diagnostic test method can be performed as part of an optical emission spectroscopy analysis workflow. Alternatively, the diagnostic test method can be performed as part of a maintenance workflow for the optical emission spectrometer.

[0041] The method of the second aspect of this disclosure may combine any optional features and any associated advantages of the optional features discussed above with respect to the first aspect of this disclosure.

[0042] According to a third aspect of this disclosure, a spectrometer is provided. The spectrometer includes a plasma source, a detector, and a controller. The spectrometer is configured to perform diagnostic tests on the detector. The controller is configured to cause the spectrometer to perform a plurality of detector diagnostic measurements, wherein for each diagnostic detector, the measurements are as follows:

[0043] The detector is configured to measure the intensity of a first spectral line emitted by elements of the plasma source;

[0044] The detector is configured to measure the intensity of a second spectral line emitted by the element of the plasma source;

[0045] The first and second spectral lines emitted by the elements of the plasma source form a branched spectral line pair.

[0046] The controller is configured to perform diagnostic measurements on the plurality of detectors, controlling the spectrometer to change the intensities of the first and second spectral lines incident on the detectors. The controller is also configured to perform diagnostic measurements on each of the plurality of detectors, diagnosing the operational status of the detector based on the ratio of the intensity of the first spectral line to the intensity of the second spectral line.

[0047] Therefore, according to a third aspect of this disclosure, a spectrometer can be provided, configured to perform the diagnostic testing method of the first aspect of this disclosure. The spectrometer can also be configured to perform the light emission spectroscopy method according to the second aspect of this disclosure.

[0048] The spectrometer of the third aspect of this disclosure may combine any optional features and any associated advantages of the optional features discussed above with respect to the first or second aspect of this disclosure.

[0049] According to a fourth aspect of this disclosure, a computer program is provided. The computer program includes instructions that, when executed, cause a spectrometer of the third aspect of this disclosure to perform a diagnostic testing method according to the first aspect of this disclosure or a light emission spectroscopy method according to the second aspect of this disclosure.

[0050] According to a fifth aspect of this disclosure, a computer-readable medium is provided having a computer program of the fourth aspect stored thereon. Attached Figure Description

[0051] Embodiments of this disclosure will now be described by way of example only with reference to the accompanying drawings, in which:

[0052] - Figure 1 A schematic diagram of a spectrometer according to an embodiment of the present disclosure is shown;

[0053] - Figure 2 An illustrative diagram is shown of the excited species that produce branched spectral line pairs;

[0054] - Figure 3a An example flowchart of a diagnostic testing method according to an embodiment of the present disclosure is shown;

[0055] - Figure 3b An example flowchart of a diagnostic testing method according to another embodiment of the present disclosure is shown;

[0056] - Figure 4 A graph showing the intensity of branched spectral line pairs at different plasma source power levels is presented;

[0057] - Figure 5 It shows the drawing relative to each other. Figure 4 and 6 A graph of the intensity;

[0058] - Figure 6 A graph showing the intensity of branched spectral line pairs for different atomizer gas flow rates is presented;

[0059] - Figure 7 The spectral line intensity plots of Ar branch II are shown, obtained by optical emission spectrometers for different nebulizer gas flow rates (NGFR).

[0060] - Figure 8 It shows: a) drawn relative to each other Figure 7 The spectral line intensity plot and the residual plot for each spectral line shown in section b) of a); and

[0061] - Figure 9 Shown are: a) spectral line intensity plots of Ar branch III obtained by optical emission spectrometers for different atomizer gas flow rates plotted relative to each other, and b) residual plots of each spectral line shown in part a). Detailed Implementation

[0062] According to embodiments of the present disclosure, a spectrometer 10 is provided. The spectrometer 10 is configured to perform diagnostic testing methods according to embodiments of the present disclosure. Figure 1 A schematic diagram of the spectrometer 10 is shown. (e.g.) Figure 1 As shown, the spectrometer 10 includes a line spectral source 11, an optical device 12, a detector 13, a processor (μP) 14, a memory 15, and an input / output (I / O) unit 16.

[0063] exist Figure 1 In one embodiment, the line spectral source 11 is a plasma source such as an inductively coupled plasma (ICP) source. In other embodiments, the line spectral source 11 may be a furnace that generates excited species or any other high-temperature light source. Figure 2 An illustrative diagram showing the possible excited states of the species within line spectral source 11 is presented. For example, in Figure 1 In ICP sources, the excitation species can be elements of the plasma gas. For example... Figure 2 As shown, under different populations n1, n2, and n3, the excited species can have multiple different excited states (represented by exponents 1, 2, and 3), and under population n0, the excited species can have a ground state (represented by exponent 0). Figure 2 As shown, the transition of the excited species between the higher-level excited state (3) and the lower-level energy states (2, 1, 0) results in emission with a corresponding energy level change (hν). 32 ,hν 31 ,hν 30 Photons with energy of ) are emitted. Each spectral line (I) is emitted. 32 I 31 I 30 The relative strength of ) and the corresponding transition probability (A) 32 A 31 A 30 This is directly proportional to the energy level. It should be understood that excited species in a relatively high-level excited state (e.g., 3) can transition to more than two different energy levels (e.g., 2, 1, or 0). Therefore, excited state energy levels can produce more than one branched spectral line pair. For example, as... Figure 2 As shown, the transition between excited state energy levels three produces the first branch spectral line pair I. 32 and I 31 and the second branch spectral line pair I 32 and I 30In some embodiments, it is preferable to select branched spectral line pairs for analysis, wherein none of the spectral lines are resonance lines. For example, in Figure 2 In the example, the second branch contains spectral line I. 30 The spectral lines are resonance lines and therefore may be prone to self-absorption. Some spectral lines originating from transitions to excited overloaded levels (metastable levels) may also be prone to self-absorption.

[0064] exist Figure 1 In some embodiments, the optical element 12 may include an echelle grating and a prism (and / or an additional grating) to generate an echelle grating spectrum of light generated by the line spectral source 11. An image of the two-dimensional echelle grating spectrum is formed on the detector 13. Therefore, the optical element is configured to generate an echelle grating spectrum on the detector 13. It should be understood that the optical element 12 is configured to direct radiation from the line spectral source 11 to the detector such that the radiation is suitable for detection by the detector 13. Therefore, in other embodiments where the detector does not detect the echelle grating spectrum, the optical element 12 may be adapted to deliver radiation of a desired form to the detector 13.

[0065] exist Figure 1 In some embodiments, detector 13 may be a CCD (charge-coupled device) array. A typical CCD array may have at least approximately 1024 × 1024 pixels (1 megapixel). The CCD array may be arranged to generate spectral intensity values ​​corresponding to the measured light quantity of a mid-echelon grating spectrum and to transmit the spectral values ​​to processor 14. Therefore, detector 13 may be a multi-channel detector configured to detect multiple different wavelengths. Detector 13 (as in...) Figure 1 In one embodiment, detector 13 can be configured to detect the echelle grating spectrum. In other embodiments, detector 13 can be a CMOS or CID detector.

[0066] In some embodiments, detector 13 may be a single-channel device such as a photomultiplier tube (PMT). Optics 12 may be used to perform wavelength selection and filtering. Thus, in some embodiments, optics 12 may be used to select a first spectral line or a second spectral line incident on detector 13. Processor 14 may be configured to control optics 12 to select the wavelength of light that can be incident on detector 13.

[0067] Processor 14 (controller) may include a commercially available microprocessor or the like. Memory 15 may be a suitable semiconductor memory and may be used to store instructions that allow processor 14 to execute embodiments of the methods according to this disclosure. Processor 14 and memory 15 may be configured to control the spectrometer to execute diagnostic test methods according to embodiments of this disclosure. Therefore, memory 15 may include instructions that, when executed by processor 14, cause the spectrometer to execute diagnostic test methods according to embodiments of this disclosure.

[0068] Next, we will refer to Figure 3a This describes a diagnostic testing method for detector 13. The diagnostic testing method can be developed by... Figure 1 The spectrometer 10 shown can be operated with user intervention or completely automatically.

[0069] Initially, in step 101, the processor 14 selects a pair of branched spectral lines emitted by the line spectral source 11 for use in a diagnostic testing method. Therefore, the processor 14 selects a first spectral line and a second spectral line to be measured. Figure 1 In this embodiment, the selected branched spectral line pair may correspond to a branched spectral line pair emitted by the excitation element of the plasma gas within the ICP plasma source. The wavelengths of branched spectral line pairs used for plasma sources and other line spectral sources are well known to those skilled in the art. For example, many branched spectral line pairs have been identified in PSDOIDGE et al., 1999, or can be easily found in spectral line databases such as the NIST Atomic Spectroscopy Database. The processor 14 can select the branched spectral line pair to be measured according to the method from a predetermined list of spectral line wavelengths stored in the memory 15. Alternatively, before the diagnostic test method begins, the user can select the branched spectral line pair to be measured in the diagnostic test method as input to the processor 14.

[0070] Next, in step 102, multiple detector diagnostic measurements may be performed. Each detector diagnostic measurement includes measuring the intensity of a first spectral line emitted by the line spectral source 11 using detector 13. The multiple detector diagnostic measurements also include measuring the intensity of a second spectral line emitted by the line spectral source 11 using detector 13. Thus, detector 13 measures the two spectral lines associated with the branched spectral line pair initially selected by processor 14.

[0071] As the intensities of the first and second spectral lines change, detector 13 repeatedly measures the intensity of the first and second spectral lines. Spectrometer 10 (e.g., processor 14) can, for example, change the intensity of the first and second spectral lines by controlling line spectral source 11. Figure 1In some embodiments, the intensity of the branched spectral line pairs can be varied by controlling the power supplied to the line spectral source 11. In the case of an ICP spectral source, the power can be varied, for example, between 800 W and 1600 W at regularly spaced intervals (e.g., 200 W intervals), where measurements of the branched spectral line pairs can be performed at each interval. In some embodiments, only a single measurement of each of the first and second spectral lines can be performed at each intensity level, while in other embodiments, multiple measurements (i.e., repeated measurements) can be performed at each intensity level. Performing multiple measurements allows diagnostic testing methods to minimize shot noise components in the measurements, thereby improving the accuracy of the tests.

[0072] exist Figure 3a In this embodiment, the intensity measurements of the first and second spectral lines are performed simultaneously. By performing the measurements of the first and second spectral lines simultaneously, the flicker noise present in the measurement of the first spectral line will be correlated with the noise present in the measurement of the second spectral line. The ratio of these two measurements will not be affected by the flicker noise component. Therefore, compared to performing asynchronous measurements, performing simultaneous measurements of the first and second spectral lines allows the linearity of detector 13 to be determined with improved accuracy.

[0073] Of course, in other embodiments where detector 13 (e.g., a detector including a photomultiplier tube) is not configured to simultaneously measure light of different wavelengths, the measurements of the first and second spectral lines can be performed at different times. In some embodiments where the first and second spectral lines of each branch spectral line pair are measured asynchronously, for each detector diagnostic measurement, the second spectral line can be measured directly after the first spectral line under the same experimental conditions (e.g., power level). By measuring the spectral lines in this manner, the flicker noise present in the first and second spectral lines can be more closely correlated, thereby improving the accuracy of the diagnostic testing method.

[0074] Figure 4 A graph showing the intensities of the first and second spectral lines is displayed. Figure 4 As shown, the nebulizer gas flow rate is varied to perform multiple diagnostic detector measurements at different spectral line intensities. In some embodiments, a single measurement for each spectral line is performed at each intensity. In other embodiments, multiple diagnostic detector measurements can be performed at each intensity setting if desired. Figure 4 The data points shown are generated by simulating the spectral line intensities of different atomizer gas flow rates, and are examples of data generated in embodiments of the present invention.

[0075] After performing multiple detector diagnostic measurements, the processor 14 can diagnose the operational status of the detectors based on these measurements. For example... Figure 3aAs indicated in step 103, one method for diagnosing the operational status of the detector is to plot each measured intensity of the second spectral line relative to the corresponding measured intensity of the first spectral line. Figure 5 An example of this type of graph is shown in the figure. Figure 5 It shows Figure 4 and Figure 6 The data is plotted. Those skilled in the art will understand that, since the ratio of the transition probability to the spectral response of the two spectral lines is constant, the intensity plot of the spectral lines should form a linear relationship. In cases where the intensity of the spectral lines does not form a linear relationship or there is widespread scattering, the processor 14 can diagnose that the detector is not functioning as expected (abnormal operating condition).

[0076] Therefore, in step 104, for each of the multiple detector diagnostic measurements, the processor 14 diagnoses the operating condition of the detector 13 based on the constancy of the ratio of the intensity of the first spectral line to the intensity of the second spectral line (or in other words, the proximity of the measured intensity point to the straight line, where the slope is defined by the transition probability and the spectral response value).

[0077] For example, in some embodiments, for intensity measurement pairs (e.g., I) 32 / I 31 The processor 14 can then calculate the regression line parameters. These parameters can be calculated using ordinary least squares or, preferably, orthogonal least squares (see examples in: K. Danzer et al., Fresenius Journal of Analytical Chemistry, 1995, 352, 407-412; and W. Bablok and H. Passing, Journal of Automatic Chemistry, 1985, 7, 74-79) or nonparametric methods such as the Passing-Bablok method (H. Passing and W. Bablok, Journal of Clinical Chemistry and Clinical Biochemistry, 1983, 21, 709-720). The processor 14 can then calculate the residuals, which are the distances from the measurement points to the regression line obtained in the previous step. When the detector is operating under normal conditions, the calculated residuals are expected to be randomly distributed and very close to their zero-mean average. The processor can then compare each relative residual (i.e., the distance from the measurement point to the regression line divided by the distance from the corresponding point on the regression line to the origin of the graph) to a given critical value, and if one or more of the calculated relative residuals exceed the critical value, the processor 14 can determine that the detector is malfunctioning. For example, the predetermined critical value can be stored in memory 15 or can be specified by the user using the processor 14.

[0078] In some embodiments, the standard deviation of the residuals can be used to test detector operation using the F-test, as described in, for example, “Is My Calibration Linear?”, Analyst, November 1994, Vol. 119, pp. 2363-2366, and IUPAC “Guidelines For Calibration in Analytical Chemistry”, Pure & Appl. Chemistry, Vol. 70, No. 4, pp. 993-1014, 1998. Other methods for analyzing the intensity ratios of each pair of intensity ratios can also be used. For example, other methods for analyzing regression line residuals are further described in “EMVA Standard 1288 Standard for Characterization of Image Sensors and Cameras”, version 3.0, November 29, 2010.

[0079] In some embodiments, upon detecting an abnormal operating condition, processor 14 may use further statistical tests at step 104 to determine whether detector 13 is operating under an excessive noise abnormal operating condition or a nonlinear abnormal operating condition. That is, the detector may apply further statistical tests to attempt to characterize the abnormal behavior of detector 13. As discussed above, the processor may be configured to generate a regression line and calculate the residuals for each pair of intensity measurements relative to the regression line. The determination of nonlinear operating conditions and excessive noise operating conditions can be based on the analysis of the residuals of the intensity ratios. A nonlinear operating condition can be determined to occur if the residuals show a systematic error relative to the regression line. An excessive noise operating condition can be determined to occur if the residuals show a random but relatively wide distribution.

[0080] The difference between the two conditions can be easily identified through visual inspection of the residual plot, but the processor can also perform the task in a more objective and automated manner. For example, in one embodiment, the processor 14 can distinguish between the two conditions by scoring the residuals with values ​​of -1 and +1 and applying a run test to them. If there is a nonlinear relationship between the intensity values, there may be a large number of consecutive measurements above or below the regression line. In another embodiment, the processor can distinguish between nonlinear operating conditions and excessively noisy operating conditions by calculating a cumulative statistic and applying a Kolmogorov-Smirnov test to it, as described in: H. Passing, W. Bablok, Journal of Clinical Chemistry and Clinical Biochemistry, 1983, 21, 709-720. For each test, the threshold can be specified by the user or stored in memory. By comparing the test results with the corresponding threshold, the processor 14 determines whether the detector 13 (which has been determined to be operating under abnormal operating conditions) is operating under nonlinear operating conditions or abnormal operating conditions.

[0081] exist Figure 3b An embodiment of a method in which the spectrometer 10 uses further statistical tests to determine whether the detector 13 is operating under an abnormal condition of excessive noise or nonlinearity at step 104 is shown.

[0082] In some embodiments, the processor 14 uses the calculated intensity ratio to determine whether the detector 13 is operating under abnormal or normal conditions. In some embodiments, the processor 14 may compare the calculated intensity ratios with each other or with a ratio of known transition probabilities. An abnormal operating condition can be determined if the difference between the intensity ratios or the difference between the calculated intensity ratio and a known ratio exceeds a predetermined threshold. The predetermined threshold on which the processor 14 determines the abnormal operating condition may be specified as an absolute value or, for example, a relative amount (i.e., a percentage) of a known ratio. For example, in one embodiment, the processor 14 may determine the calculated ratio (K') at the nth measurement. n If the difference between the detector and a known ratio (K) exceeds a predetermined threshold α%, an abnormal operating condition can be identified. In other embodiments, the threshold may be 10%, 5%, 3%, 2%, 1%, 0.5%, or 0.1%. The specified threshold can reflect the expected accuracy of the detector. In some embodiments, the threshold to be used by the processor 14 can be specified by the user before the diagnostic test method begins. If the detector operates within the range specified by the threshold, the processor 14 can determine that the detector's operating condition is normal (i.e., linear).

[0083] As discussed above in step 102, spectrometer 10 performs multiple detector diagnostic measurements. In some embodiments, spectrometer 10 performs at least two detector diagnostic measurements. In other embodiments, spectrometer 10 performs at least three, five, seven, or nine detector diagnostic measurements. Increasing the number of measurements performed by spectrometer 10 can improve the significance of the statistical tests used and thus the accuracy of the diagnostic testing method in determining whether detector 13 operates linearly.

[0084] In step 105, the processor may perform a brief check to see if the diagnostic test method has been performed within the appropriate operating range of the detector. If the diagnostic test method has not been performed within a sufficiently wide operating range, the processor may instruct the spectrometer 10 to perform further detector diagnostic measurements to increase the range within which the diagnostic test method can be performed.

[0085] Therefore, processor 14 can determine the operating status of detector 13 based on the measurement data of spectral line intensity. Figure 3a and 3b In this embodiment, the determined operating condition can be that the detector operates in a linear manner or that the detector operates abnormally. If the operating condition of the detector is determined to be linear, the diagnostic test of detector 13 ends and the operating condition of detector 13 is not further investigated.

[0086] like Figure 3a and 3b As shown, if the initial determination is that the detector 13 is malfunctioning, a series of further checks and analyses can be performed. These checks and analyses are optional; therefore, in some embodiments, the determination of nonlinear behavior can lead to the termination of the diagnostic test, with output provided to the user for further investigation of the detector 13's operation. Thus, the diagnostic testing method using the spectrometer 10 allows the user to quickly identify whether the detector 13 is operating as expected. This, in turn, allows the user to quickly identify whether the detector's malfunction can be eliminated from the fault-finding procedure or whether further investigation of the detector's operation is necessary.

[0087] As mentioned above, in Figure 3a and 3b In cases where the detector's operation is determined to be nonlinear, a series of further checks and analyses can be performed. (As mentioned above...) Figure 3b The spectrometer discussed here can determine whether abnormal operating conditions are the result of excessive noise. Upon detecting excessive noise, the spectrometer 10 can output a notification and terminate the diagnostic process.

[0088] The spectrometer 10 can also undergo further checks. These checks are particularly useful for determining the detector's operation under nonlinear conditions. Figure 3a and Figure 3b In step 106, the processor 14 can check whether the measured branched spectral line pairs have undergone self-absorption. The processor 14 can check for self-absorption by comparing the wavelength of the spectral line measured as part of multiple detector diagnostic measurements with a list of known spectral lines known to be prone to self-absorption. The list of known spectral lines can be stored in memory 15. In some embodiments, the processor 14 can also check individual measurements of the spectral line pairs to see if the expected intensity relationship between the measured spectral line pairs is maintained. That is, the processor 14 can predict the expected intensity of a spectral line based on the intensity of one or more other spectral lines measured. If the expected intensity of a second spectral line does not properly match the measured intensity of the second spectral line, the processor 14 can determine that self-absorption has occurred. In some embodiments, the spectrometer 10 can be configured to perform multiple detector diagnostic measurements using light emitted radially and axially from a plasma source. That is, the line spectral source can emit light in mutually orthogonal directions by illuminating the detector 13 with light from a line spectral source generated in two mutually orthogonal directions. In this way, self-absorption can be detected by comparing the detector diagnostic measurements of light in the first direction with those of light generated in the second orthogonal direction.

[0089] If processor 14 determines that self-absorption has occurred using one or more of the criteria discussed above, processor 14 can determine that a different branched spectral line pair should be selected for step 101 and that the diagnostic test method should be repeated using a different branched spectral line pair. Therefore, the diagnostic test method can automatically alert the user and correct for the occurrence of self-absorption.

[0090] If processor 14 does not detect any self-absorption using any of the aforementioned criteria, the processor can determine that the nonlinearity detected in the intensity measurement is not a result of self-absorption. In some embodiments, processor 14 can then determine that detector 13 is operating nonlinearly and further investigation may be necessary. Figure 3a and 3bAs shown, processor 14 can also perform analysis at step 107 to see if line positioning errors have occurred during or before the multiple detector diagnostic measurements. Line positioning errors may occur in some detectors 13, such as echelle grating detectors. Line positioning errors occur when the measured position of a spectral line differs from the expected position of the spectral line on the echelle grating detector. The position of the spectral line may deviate due to drift. Drift may occur due to temperature changes in the angle or relative distance between the grating in the optical element or between the grating and the prism in the optical element, resulting in a change in the position of the echelle grating spectral peak. Due to line positioning errors, the peak corresponding to the spectral line may not be identified or may be measured incorrectly.

[0091] Various methods for detecting and correcting line positioning errors are known to those skilled in the art. For example, in some embodiments, a spectrometer may adjust a measured pixel pattern to a desired line profile (step 108). The spectrometer may adjust detector 13 and / or optics 12 to correct previously detected line positioning errors. In other embodiments, the measured intensity may be recalibrated to correct detected pixel offsets. Further discussion of some of the possible methods by which those skilled in the art can correct or resolve line positioning errors is disclosed in US 6,029,115 and US 7,319,519.

[0092] like Figure 3a and 3b As shown in the embodiment, in the event of a detected line positioning error, the measurement pixel pattern is adjusted to address the offset of spectral line positioning in the echelle grating spectrum, and multiple detector diagnostic measurements are repeated (step 102). Figure 3a and 3b In the embodiment where no line positioning error is detected, processor 14 determines that the detector is malfunctioning, and processor 14 cannot determine any reason why this is happening. Therefore, processor 14 flags detector 13 as potentially malfunctioning to the user.

[0093] Therefore, a diagnostic testing method for spectrometers is provided. As described above and as... Figure 3a and 3b The diagnostic testing method illustrated allows users to quickly and effectively determine whether a detector is operating in a linear or non-linear manner. It should be understood that the workflow steps can be performed in a different order than that given above.

[0094] As mentioned above, in Figure 3a and 3bIn one embodiment, the processor 14 controls the spectrometer to change the intensity of the first and second spectral lines. Of course, in other embodiments, the processor 14 may control other parameters of the spectrometer 10 to change the intensity of the first and second spectral lines. Figure 6 An example of a change in spectral line intensity measured in response to a change in power supplied to an ICP light source is shown. From Figure 6 It should be understood that changing the spectrometer parameters to control the intensity of spectral lines does not require a linear relationship between the parameters and the measured intensity of a spectral line. However, due to the fixed relationship between the expected transition probabilities, the relationship between the intensity of the first spectral line and the intensity of the second spectral line will be linear. Figure 6 The simulation of the spectral line intensities of the first and second spectral lines under different powers supplied to the ICP light source is shown by way of example.

[0095] In other embodiments, one or more optical elements of the optics 12 can be controlled to change the intensity of the line spectral source incident on the detector 13. Therefore, the diagnostic testing methods of this disclosure are not limited to the instances of changing the intensity of the first and second spectral lines discussed above.

[0096] exist Figure 3a and 3b In one embodiment, in step 101, a single branch spectral line pair is selected for measurement during the diagnostic testing method. In other embodiments, more than one branch spectral line pair can be measured. By measuring different branch spectral line pairs, the operating status of the detector can be determined within different wavelength ranges. This expands the number of test pixels (channels) and the range of measured intensity when the detector to be diagnosed is a multi-channel detector. Therefore, in some embodiments, in step 101, multiple branch spectral line pairs can be selected for analysis using the method described above.

[0097] Therefore, in some embodiments, the diagnostic testing method may include performing additional multiple detector diagnostic measurements using different spectral line pairs emitted by the excitation species of the line spectral source. The different spectral line pairs emitted by the excitation species of the line spectral source form different branched spectral line pairs. Different spectral line pairs may be emitted by the same excitation species, for example, in... Figure 2 In the example, the first spectral line pair can be hν 32 and hν 31 The second (different) branch spectral line pair is hν 32 and hν 30In some embodiments, different spectral line pairs can be used instead of the first and second spectral lines to completely replicate the diagnostic test method. In other embodiments, different spectral line pairs can be measured simultaneously (synchronously) with or sequentially after the first and second spectral lines in step 102. The operating condition can then be determined by considering the measurement of the two spectral line pairs or based on the wavelengths (corresponding to the wavelengths of the first, second, third, and fourth spectral lines).

[0098] Figure 7 An example of experimental measurements obtained by an ICP optical emission spectrometer is shown. According to embodiments of this disclosure, the experimental measurements can be used as part of a diagnostic testing method. Figure 7 The intensities of the Ar branch II spectral lines λ1 = 427.217 nm, λ2 = 416.418 nm, and λ3 = 456.610 nm are shown for different nebulizer gas flow rates (NGFR). (Repeat) Figure 7 The measurements were taken three times as shown.

[0099] Figure 8 It shows the drawing relative to each other. Figure 7 The spectral line intensity diagram. For example... Figure 8 The intensities of spectral lines λ2 and λ3 are plotted relative to λ1. Measurements are repeated (three times) at each NFGR. Figure 8 As shown, the orthogonal distance regression (ODR) line is calculated for each branch pair (λ1, λ2; λ1, λ3). Figure 8 The illustration shows a detailed view of a portion of the regression line of the λ1, λ2 plots. The locations of the experimental points corresponding to repeated measurements demonstrate the accuracy observable according to the diagnostic method of this disclosure. Although flicker noise is present in each individual measurement under the same experimental conditions (here, constant NGFR), the experimental points are not randomly scattered but lie on the same regression line. This contrasts with the relatively small deviation of the rest of the ODR line (…). Figure 8 The percentage (less than 0.06%) can be attributed to shot noise. Figure 8 The ODR lines shown are calculated using NISTDATAPLOT software and are used herein to illustrate the principles of the invention.

[0100] It should be understood that other techniques can be used alternatively to construct similar regressions, such as those mentioned above. Figure 5 The methods of discussion.

[0101] Figure 8The lower part (labeled b) shows the relative distance between the experimental measurement point and the regression line for each experimental measurement. It can be seen that the mode is primarily controlled by shot noise. Therefore, the system can be considered linear over a range exceeding five orders of magnitude, with only shot noise control accuracy (i.e., less than 0.1% for the highest half of the operating range).

[0102] Figure 9 The diagram shows the intensity plots of branched spectral lines measured by detectors for different nebulizer gas flow rates (NGFR), where the lines belong to Ar branch family III. Experimental points corresponding to a single repeat overlap in the plot showing relative distances. While exhibiting linear behavior with a deviation of less than 0.1% for the spectral line ratios λ1 and λ3, the intensity residuals of the spectral line ratio lines λ1 and λ2 (known to be caused by transitions to metastable levels and therefore prone to self-absorption) show a distinct nonlinear characteristic. Therefore, in step 106 of the method according to this disclosure, processor 14 can determine that the measured branched spectral line pair experiences self-absorption. Processor 14 can examine the self-absorption phenomenon and confirm that λ2 is prone to self-absorption by comparing the wavelength of the spectral line measured as part of multiple detector diagnostic measurements with a list of known spectral lines. The list of known spectral lines can be stored in memory 15. Therefore, in some embodiments, the method can discard branched spectral line measurements containing spectral line λ2. Such spectral lines can also be a priori excluded before measurement because such spectral lines are unsuitable for use in tests under selected conditions.

[0103] Therefore, embodiments of this disclosure provide a diagnostic testing method for a detector of a spectrometer including a line spectral source. Using a line spectral source in the diagnostic testing method allows the diagnostic testing method to be performed with improved accuracy and efficiency.

Claims

1. A fault diagnosis test method for a detector in a spectrometer, the spectrometer comprising a line spectral source configured to emit at least one branched spectral line pair from an excited species. The fault diagnosis test method includes: Perform diagnostic measurements using multiple detectors; Each detector diagnostic measurement includes: The detector is used to measure the intensity of the first spectral line emitted by the excited species from the line spectral source; and The detector is used to measure the intensity of the second spectral line emitted by the excited species from the line spectral source; The first spectral line and the second spectral line emitted by the excited species of the line spectral source form a branched spectral line pair; For diagnostic measurements of the plurality of detectors, the spectrometer is controlled to change the intensity of the first and second spectral lines incident on the detectors; and For each of the plurality of detector diagnostic measurements, the operational status of the detector is diagnosed based on the ratio of the intensity of the first spectral line to the intensity of the second spectral line. When it is determined that the ratio of the intensity of the first spectral line to the intensity of the second spectral line forms a linear relationship for each of the plurality of detector diagnostic measurements, a normal operational status of the detector is diagnosed. When it is determined that for each of the plurality of detector diagnostic measurements, the ratio of the intensity of the first spectral line to the intensity of the second spectral line forms a non-linear relationship, an abnormal operating condition of the detector is diagnosed.

2. The fault diagnosis test method according to claim 1, wherein... For diagnostic measurements of the plurality of detectors, at least one of the following is controlled: the line spectral source, the detector, and one or more optical elements between the line spectral source and the detector, to change the intensity of the first spectral line and the second spectral line incident on the detector.

3. The fault diagnosis test method according to claim 1 or claim 2, wherein... The line spectral source is a plasma source.

4. The fault diagnosis test method according to claim 3, wherein... Controlling the plasma source to change the intensity of the first and second spectral lines includes controlling one or more of the following: plasma power, plasma gas flow rate, atomizer gas flow rate, and cooling gas flow rate.

5. The fault diagnosis test method according to any one of claims 1-2 and 4, wherein... The intensity of the first spectral line is measured simultaneously with the intensity of the second spectral line.

6. The fault diagnosis test method according to any one of claims 1-2 and 4, further comprising: Additional detector diagnostic measurements are performed using different spectral lines emitted by the excited species from the said line spectral source. The different spectral line pairs emitted by the excited species of the line spectral source form branched spectral line pairs that are different from the first spectral line and the second spectral line.

7. The fault diagnosis test method according to claim 1, wherein... In the event of the abnormal operating condition being diagnosed, the method further includes, for each of the plurality of detector diagnostic measurements, diagnosing a nonlinear operating condition or an excessively noisy operating condition based on the ratio of the intensity of the first spectral line to the intensity of the second spectral line.

8. The fault diagnosis test method according to claim 1, wherein... A linear relationship is determined when each of the ratios determined by diagnostic measurements for the plurality of detectors falls within a predetermined range.

9. The fault diagnosis test method according to claim 7, wherein... If the nonlinear operating condition is diagnosed, the fault diagnosis test method further includes: Determine whether the first spectral line and / or the second spectral line that form the branched spectral line pair undergo self-absorption.

10. The fault diagnosis test method according to claim 9, wherein... If self-absorption is determined for the first spectral line and / or the second spectral line, the fault diagnosis test method is repeated using different branch spectral lines with different wavelengths.

11. The fault diagnosis test method according to any one of claims 7, 9 to 10, wherein If the nonlinear operating condition is diagnosed, the fault diagnosis test method further includes: Determine whether the measurement of the first spectral line and / or the measurement of the second spectral line has experienced line positioning error.

12. The fault diagnosis test method according to claim 11, wherein... If a line positioning error is determined to have occurred: Adjust the spectrometer to reduce line positioning error, and repeat the multiple detector diagnostic measurements, or The measurements of the first and second spectral lines are recalibrated to address the line positioning error, and for each of the plurality of detector diagnostic measurements, the operating condition of the detector is determined based on the ratio of the recalibrated intensity of the first spectral line to the recalibrated intensity of the second spectral line.

13. The fault diagnosis test method according to any one of claims 1-2, 4, 7-10, and 12, wherein... The fault diagnosis test method is performed on one or more of the following: Photomultiplier tube detectors, charge-coupled device detectors, complementary metal-oxide-semiconductor detectors, and charge injection device detectors.

14. The fault diagnosis test method according to any one of claims 1-2, 4, 7-10, and 12, wherein the excitation species is provided by one or more of the following: A standard solution of known concentration nebulized into the plasma; or Plasma gas species.

15. A method for optical emission spectroscopy of a spectrometer, the spectrometer comprising a plasma source and a detector, the method comprising a fault diagnosis test method according to any one of claims 1 to 14.

16. A spectrometer comprising: A line spectral source configured to emit at least one branched spectral line pair from an excited species; Detector; as well as Controller The controller is configured to cause the spectrometer to perform a fault diagnosis test on the detector, the fault diagnosis test including: The spectrometer performs multiple detector diagnostic measurements, wherein the measurements are performed for each diagnostic detector: The detector is configured to measure the intensity of a first spectral line emitted by the excited species from the line spectral source; The detector is configured to measure the intensity of a second spectral line emitted by the excited species from the line spectral source; The first spectral line and the second spectral line emitted by the excited species of the line spectral source form a branched spectral line pair; The controller is configured to perform diagnostic measurements on the plurality of detectors, and to control the spectrometer to change the intensity of the first and second spectral lines incident on the detectors; and The controller is configured to diagnose the operational status of the detector for each of the plurality of detector diagnostic measurements based on the ratio of the intensity of the first spectral line to the intensity of the second spectral line, wherein a normal operational status of the detector is diagnosed when it is determined that the ratio of the intensity of the first spectral line to the intensity of the second spectral line forms a linear relationship for each of the plurality of detector diagnostic measurements. When it is determined that for each of the plurality of detector diagnostic measurements, the ratio of the intensity of the first spectral line to the intensity of the second spectral line forms a non-linear relationship, an abnormal operating condition of the detector is diagnosed.

17. A computer program comprising instructions that, when executed, cause a spectrometer according to claim 16 to perform the fault diagnosis test method according to any one of claims 1 to 14 or the optical emission spectroscopy method according to claim 15.

18. A computer-readable medium having a computer program stored thereon according to claim 17.

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