Top 10 Common Questions for Spectrometer Selection (Part 2)

When building a spectral detection system or selecting a spectrometer—whether you are a researcher, engineer, or system integrator—you will inevitably face a series of selection challenges.

In the previous article, we discussed five core selection issues: spectral range, resolution, cooling type, slit, and interfaces. In this installment, we will dive deeper into five additional common questions that are crucial when setting up a spectral system.

Q6: How do I choose the matching fiber optic and light source?
A: Fiber optics and light sources are the "blood vessels" and "heart" of a spectral system. Choosing them correctly ensures efficient and accurate signal transmission.

Three Key Factors for Fiber Selection :
Core Diameter: Bigger is not always better; it needs to match the spectrometer's detector.

• Linear array CMOS detectors (e.g., SR50C, SR75C): A 200 μm core diameter fiber is recommended for optimal coupling.
• Area array CCD detectors (e.g., SR100B, SR100Z, ST90S): A larger core diameter of 400 μm or 600 μm, or multi-core fibers, can be chosen to collect more light signals.

Material and Wavelength Band: Select the fiber material based on the operating wavelength to avoid transmission loss.

• UV/VIS: Use High-OH (high hydroxyl) quartz fiber.
• NIR: Use Low-OH (low hydroxyl) quartz fiber.
• Deep UV: Requires specialized UV-resistant fiber.

Numerical Aperture (NA): Should match the NA of the spectrometer's internal optical components as closely as possible to avoid light energy loss. JINSP's transmission spectrometers (ST series) have an NA of 0.25, which perfectly matches the industry-standard 0.22 NA multimode fiber.

Light Source Selection: Based on detection principle and wavelength band.

• Absorption/Reflectance/Transmission Measurements: Requires a broadband, stable continuous light source.
• UV-VIS-NIR full range: Deuterium-Halogen light source is recommended (e.g., DH-01, 190–2500 nm) .
• VIS-NIR: Tungsten-Halogen light source is recommended (e.g., HL series, 360–2500 nm).
• Fluorescence Measurements: Requires a specific wavelength excitation source, such as an LED or laser.
• Raman Measurements: Must use a laser with good monochromaticity (532 nm, 785 nm, 1064 nm, etc.) .
• LIBS Measurements: Requires a high-power pulsed laser as the excitation source.

Matching Recommendations:
JINSP can provide complete system solutions. For example, the Spectrometer Application Manual clearly lists standard configurations (spectrometer + light source + fiber + holder) for different measurement systems like reflectance, transmittance, fluorescence, and LIBS, allowing users to reference them directly based on their application scenario.

Q7: What is the software and SDK support like for the spectrometer?
A: Software is the interface for users to interact with the spectrometer, while the SDK (Software Development Kit) is key for system integration and secondary development.

Standard Software:
JINSP provides all spectrometers with the self-developed "JINSP_SPEC" spectral acquisition and analysis software. This software supports real-time spectral display, data saving (CSV, TXT, etc.), parameter settings (integration time, averaging times etc.), and basic absorbance and transmittance calculations. The software interface supports both Chinese and English.

SDK and Secondary Development Support:

• Supported Scope: All models come with an SDK, supporting mainstream programming languages such as C/C++, LabVIEW, MATLAB, Python, and Java, making it easy for users to integrate the spectrometer into automated testing systems or their own software platforms.
• Protocol Support: In addition to standard USB communication, all spectrometers provide the Modbus communication protocol, facilitating integration with industrial equipment like PLCs.
• Operating System Compatibility: Currently, the software primarily supports Windows 10 and above.

Q8: Does a fixed-grating spectrometer require wavelength calibration? How is it done?
A: For spectrometers with a fixed grating design (such as JINSP's SR and ST series), the wavelength stability is extremely high, and under normal use, subsequent wavelength calibration by the user is typically unnecessary. Precise calibration has been completed at the factory, and the calibration coefficients have been permanently stored (embedded) within the device.

Why is the fixed-grating design more stable?
The optical components (such as the grating and mirrors) of a fixed-grating spectrometer are precisely fixed and sealed at the factory, with no movable mechanical parts. This design fundamentally avoids wavelength drift caused by vibration, wear, or mechanical loosening, thus providing excellent long-term stability.

When might verification or operation be needed?

• Factory Verification: Before leaving the factory, the manufacturer uses standard light sources like Mercury-Argon (Hg-Ar) lamps for rigorous wavelength calibration, ensuring wavelength accuracy (e.g., within ±0.3–0.5 nm error) and generating a calibration report.
• Verification in Extreme Cases: If the device has been subjected to extreme environments (e.g., severe temperature shocks, strong vibrations) or after long-term use (e.g., several years), users may perform verification if they have doubts about wavelength accuracy.
• Verification for Ultra-High Precision Requirements: Users may self-verify before conducting experiments with extremely high requirements for absolute wavelength accuracy.

Verification/Operation Method (if needed) :
Use a Standard Light Source: Connect a Mercury-Argon (Hg-Ar) lamp, which provides known and stable characteristic emission lines (e.g., Mercury line at 253.6 nm, Argon line at 696.5 nm).

Acquire and Compare: Use the spectrometer to collect the spectrum of the standard light source. Use the accompanying software (e.g., JINSP_SPEC) to check if the detected characteristic peak positions match the theoretical values. The software typically has automatic comparison or fitting functions.

Result Judgment: If the peak wavelength error is within the device's specified accuracy range (e.g., ±0.5 nm), the wavelength status is good and no action is needed. If a deviation is found to be out of range, contact the manufacturer's technical support rather than adjusting it yourself, as calibration of fixed-grating spectrometers typically needs to be done in a factory environment.

Calibration Cycle Recommendation:
For regular use, thanks to the inherent stability of the fixed grating, there is no need to set a fixed manual calibration cycle.

Q9: Is customization supported (wavelength range, interfaces, structure)?
A: Yes. JINSP has strong customization capabilities to meet users' specific needs.

Wavelength Range Customization: This is the most common customization request. For example, the standard model might cover 200–450 nm, but a user might need 250–500 nm to monitor peaks after 500 nm, or a specific Raman shift range. This can be achieved by changing the grating and adjusting the optical path, but the scope of changes and costs need to be assessed based on specific requirements.

Interface Customization:

• Electrical Interfaces: In addition to standard USB and serial ports, RS485, Ethernet, etc., can be customized.
• Fiber Optic Interfaces: Supports standard interfaces like SMA905 and FC/PC, and can also be adjusted according to requirements.

Structure Customization:

• Special dimensions can be customized to fit compact integration spaces.
• Multi-channel input (e.g., 4 channels, for JINSP's ST series transmission spectrometers) can be customized for simultaneous monitoring of multiple samples.
• Special probes or sampling accessories can be customized.
• Other Customizations: Such as slit width, software features (e.g., support for external triggering), etc.

Customization Process and Lead Time:
Requires detailed communication with technical support to discuss requirements. The delivery time for standard models is approximately 4–6 weeks, while custom models typically take 6–8 weeks or longer, depending on the complexity of the modifications.

Q10: How do I evaluate the long-term stability of a spectrometer?
A: Long-term stability is a key indicator of a spectrometer's reliability and data reproducibility, primarily reflected in wavelength stability and intensity stability.

Evaluating Wavelength Stability:

• Method: In a temperature-controlled environment, measure the characteristic peak positions of a standard light source (e.g., Mercury-Argon lamp) multiple times continuously or at long intervals, and calculate the standard deviation or maximum drift of the wavelength.
• Indicator: The wavelength stability of the SR50C is approximately 0.12 nm drift per 20°C. High-stability models have even better temperature drift coefficients.

Evaluating Intensity/Signal-to-Noise Ratio Stability:

• Method: Under fixed integration time and light source conditions, measure multiple times continuously and calculate the relative standard deviation (RSD) of the characteristic peak intensity.
• Indicator: The typical requirement is RSD < 1%. This reflects the combined stability of the spectrometer's detector, electronics, and light source.

Factors Ensuring Long-Term Stability:

• Optical Design: Designs with fixed gratings and no moving parts (like JINSP's fixed-grating spectrometers) offer much higher stability than tunable grating spectrometers.
• Temperature Drift Compensation: Built-in temperature sensors and compensation algorithms (e.g., in SR50C/SR75C) effectively suppress drift caused by ambient temperature changes.
• Detector Performance: Cooled detectors can significantly reduce thermal noise variations over time and temperature.

Summary:

Selecting a spectrometer is a systematic engineering task that requires comprehensive consideration—from core optical parameters (wavelength, resolution) to supporting accessories (fiber, light source), from immediate software operation to long-term stable maintenance. We hope these two installments of the "Top 10 Common Questions" can help clear the fog and provide you with a clear path for selection.

If you encounter more detailed questions when selecting for specific applications (such as chlorophyll fluorescence measurement, doped glass Raman analysis, or water quality online monitoring), feel free to contact JINSP team. We will combine your actual scenario to provide professional solutions.