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Leading manufacturer of electroacoustic test equipment, acoustic cameras, and sound & vibration measurement systems. Serving 10,000+ customers across 90+ countries with 28 years of expertise.
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Deliver reliable products for acoustic measurement and testing
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Provides measurement microphones, mouth simulators, ear simulators, and more for accurate acoustic measurements.
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Combines hardware and software for high-speed, high-precision signal acquisition, ideal for various acoustic applications.
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Offers acoustic cameras for gas leak detection, partial discharge, and fault diagnostics across handheld, fixed, and UAV platforms.
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Includes sound level meters, noise sensors, and monitoring systems for effective noise measurement and analysis.
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Why Choosing the Right Acoustic Test Chamber Matters In electroacoustic testing and wireless device production, the test chamber is not just a box — it directly affects measurement accuracy, throughput, and production costs. The wrong chamber can introduce background noise into your measurements, fail to shield RF interference, or simply not fit your DUT (Device Under Test). This guide walks you through the key factors for selecting an acoustic test chamber, with a comparison of CRYSOUND's product range to help you match the right model to your application. Key Selection Criteria 1. What Are You Testing? The size and type of your DUT is the first deciding factor: DUT TypeTypical ProductsChamber RequirementSmall wireless devicesTWS earbuds, smartphones, smart watchesCompact chamber with RF shieldingMedium devicesBluetooth speakers, headphones, smart home devicesMid-size chamber with good low-frequency isolationLarge devicesLaptops, walkie-talkies, wireless serversLarge chamber with full RF shieldingUltra-quiet testingMEMS microphones, hearing aids, high-sensitivity sensorsUltra-low noise floor chamber 2. Acoustic Isolation Performance How much noise do you need to block? If your production floor is noisy (70–80 dB ambient), you need a chamber with high sound attenuation to achieve a clean measurement environment. For laboratory settings that are already relatively quiet, a lighter chamber may suffice. Key spec to check: Sound attenuation (dB) across the frequency range relevant to your product. Pay special attention to low-frequency attenuation — this is where most chambers struggle, and where the CRY725D specifically excels. 3. RF Shielding If you are testing wireless devices (Bluetooth, WiFi, GSM, WCDMA, RFID, GPS), RF shielding is essential to prevent interference between adjacent production lines. Without it, neighbouring test stations can cause false failures. Key spec to check: Shielding effectiveness (dB) at the frequencies your device operates on. 4. Door Mechanism: Pneumatic vs Manual FeaturePneumatic DoorManual DoorSpeedFast open/close, ideal for high-volume productionSlower, suitable for lab or low-volumeAutomationSerial port / PLC control, integrates into automated linesManual operation onlyConsistencyRepeatable sealing force every cycleDepends on operatorCostHigher (requires air supply)LowerBest forProduction linesR&D labs, occasional testing 5. Production Line Integration For high-volume manufacturing, consider: Drawer-style design — slides into automated test racks (e.g. CRY7865, CRY725D) Shell-type design — pairs with analysers for multi-station operation (e.g. CRY723) Serial port control — enables software-triggered open/close for fully automated test sequences CRYSOUND Acoustic Test Chamber Lineup Here is a comparison of our full product range, organised by application scenario: For Smartphones & Wireless Wearables CRY723 Pneumatic Acoustic Test Chamber Design: Shell-type, compact form factor Best for: Smartphones, TWS earbuds, smart watches, wireless wearables Key advantage: Cost-effective and high-performance. Combine two CRY723 units with a CRY6151B analyser for complete audio, ENC, and ANC measurements — one operator manages two test stations simultaneously Door: Pneumatic CRY723D Pneumatic Acoustic Test Chamber Design: Enhanced version of CRY723 Best for: Wireless electronic and communication products requiring comprehensive RF testing Key advantage: Full wireless connectivity support — Bluetooth, WiFi, GSM, WCDMA, RFID, GPS Door: Pneumatic For Large Wireless Devices CRY725 Pneumatic Acoustic Test Chamber Design: Large-format chamber Best for: Laptops, walkie-talkies, wireless servers, and other large wireless devices Key advantage: Spacious internal volume for large DUTs, compatible with comprehensive testers and vector network analysers Door: Pneumatic CRY725D Pneumatic Acoustic Test Chamber Design: Drawer-style, enhanced low-frequency performance Best for: Background noise measurement, applications requiring superior low-frequency isolation Key advantage: Superior soundproofing at low frequencies compared to CRY725. Combined with CRY6151B and CRY algorithm, provides enhanced noise floor minimisation for precision testing Door: Pneumatic (drawer-style) For Production Line Integration CRY7865 Pneumatic Acoustic Test Chamber Design: Drawer-style, designed for rack integration Best for: Automated production lines testing Bluetooth headphones, speakers, laptops Key advantage: High-performance acoustic isolation and RF shielding in one unit. Drawer-style design facilitates seamless integration into automated test systems Door: Pneumatic (drawer) CRY710 Pneumatic Acoustic Test Chamber Design: Welded steel plate construction, robust RF shielding Best for: Bluetooth, WiFi device testing where strong RF shielding is the priority Key advantage: Prevents interference between adjacent production lines. Combine two CRY710 units with a CRY6151B for quadruplex TWS headphone audio testing Door: Pneumatic (serial port controlled) For R&D and Laboratory Use CRY7413 Acoustic Test Chamber, Manual Door Design: Compact, manual door, adjustable test jig Best for: R&D labs, product development, low-volume testing Key advantage: User-friendly design with marked and adjustable test jig that accommodates various DUT sizes. Quick DUT exchange with minimal operator strain Door: Manual CRY7412 Ultra-Quiet Chamber Design: Double-shell (box-in-box), lateral two-stage opening Best for: Testing very quiet sounds — MEMS microphones, hearing aids, high-sensitivity sensors Key advantage: Unique box-in-box design provides the lowest noise floor in the product range. Essential when your DUT produces very low sound levels that would be masked by ambient noise in a standard chamber Door: Manual (two-stage lateral opening) Quick Selection Guide Your SituationRecommended ModelWhyTesting TWS earbuds on a production lineCRY723Compact, cost-effective, dual-station with CRY6151BTesting laptops or large wireless devicesCRY725Large internal volume, full RF shieldingNeed superior low-frequency isolationCRY725DEnhanced low-frequency soundproofingAutomated production line integrationCRY7865Drawer-style, RF + acoustic shieldingBluetooth/WiFi RF isolation is priorityCRY710Robust welded steel RF shieldingR&D lab, various DUT sizesCRY7413Adjustable jig, easy DUT exchangeMeasuring very quiet soundsCRY7412Double-shell, lowest noise floor Frequently Asked Questions Do I need RF shielding in my acoustic test chamber? If you are testing any wireless device (Bluetooth, WiFi, cellular), the answer is yes. Without RF shielding, wireless signals from neighbouring test stations or production equipment can cause false test failures. All CRYSOUND pneumatic chambers include RF shielding as standard. Can I use one chamber for both R&D and production? Yes, but the optimal choice differs. For R&D, flexibility and low noise floor matter most (CRY7413 or CRY7412). For production, speed and automation matter most (CRY723, CRY7865). If you need both, consider the CRY723 — it balances performance, automation capability, and cost. What is the advantage of drawer-style vs shell-type chambers? Drawer-style (CRY7865, CRY725D) slides into standard equipment racks and integrates cleanly into automated test lines. Shell-type (CRY723) opens like a clamshell for quick DUT loading and is more versatile for varied DUT shapes. Choose drawer-style for fixed production setups; shell-type for flexible or multi-product lines. How do I reduce labour costs in acoustic testing? Combine two test chambers with a single CRY6151B electroacoustic analyser. While one DUT is being tested, the operator loads the next DUT in the second chamber. This dual-station setup — supported by CRY723, CRY710, and other models — effectively doubles throughput with no additional headcount. Need Help Choosing? Every production environment is different. If you are unsure which model fits your requirements, our engineering team can help you evaluate your testing needs and recommend the right configuration. Contact CRYSOUND for a personalised recommendation based on your DUT, production volume, and test requirements.
What Is an Anechoic Chamber? An anechoic chamber is a room designed to completely absorb sound reflections. The walls, ceiling, and (in a full anechoic chamber) the floor are lined with wedge-shaped foam or fibreglass absorbers that prevent sound waves from bouncing back into the room. The result is a controlled acoustic environment that simulates free-field conditions — as if the sound source were suspended in open air with no surfaces nearby. This matters because most acoustic measurements — sound power, directivity, frequency response — require a known, reflection-free environment to produce repeatable, standards-compliant results. Without it, room reflections contaminate the measurement, making results dependent on the specific room rather than the product being tested. Full Anechoic vs Semi-Anechoic (Hemi-Anechoic) Chambers Feature Full Anechoic Semi-Anechoic (Hemi-Anechoic) Absorbing surfaces All 6 surfaces (walls, ceiling, floor) 5 surfaces (walls + ceiling); floor is reflective Floor Wire mesh or perforated metal grid suspended above absorbers Solid, load-bearing concrete or steel Acoustic condition Free-field (no reflections from any direction) Free-field over a reflecting plane Load capacity Limited — cannot support heavy equipment directly Can support vehicles, machinery, industrial equipment Primary standards ISO 3745 (precision sound power) ISO 3744 (engineering sound power), ISO 3745 Typical use Microphone calibration, loudspeaker characterisation, hearing research Automotive NVH, product noise testing, industrial machinery Cost Higher (floor treatment adds significant cost and complexity) Lower (no floor treatment needed) In practice, about 80% of industrial acoustic testing uses semi-anechoic chambers because most test objects — cars, appliances, compressors, power tools — are too heavy for a suspended wire-mesh floor. What Standards Require an Anechoic Chamber? ISO 3745 — Precision Sound Power Measurement The gold standard for sound power determination. Requires either a full anechoic or hemi-anechoic chamber qualified to meet strict free-field deviation limits across the frequency range of interest. The chamber must demonstrate that the inverse-square law holds to within ±1 dB at the measurement positions. Typical cut-off frequency: 80–200 Hz, depending on chamber size and wedge depth. Below this frequency, the chamber no longer behaves as a free field. ISO 3744 — Engineering Sound Power Measurement Less stringent than ISO 3745 but still requires a hemi-anechoic environment. Allows for environmental corrections when the room is not perfectly anechoic, making it practical for production-floor test cells that approximate (but do not perfectly achieve) free-field conditions. ISO 26101 — Qualification of Free-Field Environments Defines how to verify whether a room actually meets free-field requirements. This is the standard used to “qualify” an anechoic or hemi-anechoic chamber — confirming that its acoustic performance matches what is claimed. Other Standards ECMA-74: IT equipment noise measurement (uses ISO 3745 or ISO 3744 as the underlying acoustic method) ANSI S12.55 / S12.56: North American equivalents of ISO 3744/3745 ISO 11201–11205: Various sound pressure level determination methods, some requiring free-field conditions Key Design Considerations 1. Chamber Size and Usable Volume The physical dimensions determine the lowest usable frequency. A general rule: the chamber must be large enough that the distance between the sound source and each measurement microphone is at least one wavelength at the lowest frequency of interest. For a 100 Hz cut-off, the minimum source-to-microphone distance is approximately 3.4 metres, which means the chamber's internal dimensions (excluding wedges) should be at least 7–8 metres per side for a hemi-anechoic chamber. 2. Wedge Absorbers The depth of the absorbing wedges determines the low-frequency performance. Deeper wedges absorb lower frequencies: Wedge Depth Approximate Low-Frequency Cut-off 200 mm ~500 Hz 500 mm ~200 Hz 1000 mm ~80–100 Hz Wedge materials include melamine foam (lightweight, fire-retardant) and fibreglass (better low-frequency absorption but heavier). 3. Background Noise An anechoic chamber must also be well-isolated from external noise. The ambient noise level inside the chamber (with no source operating) should be at least 6 dB — and preferably 15 dB — below the sound pressure level generated by the test object at the measurement positions. This typically requires a chamber built with multiple layers of massive construction (concrete, steel) and vibration-isolated mounting to prevent structure-borne noise transmission. 4. Vibration Isolation For NVH testing (especially automotive), the chamber floor may include vibration-isolated foundations or air-spring mounting systems to prevent road-simulator or dynamometer vibrations from coupling into the acoustic measurement environment. What If You Do Not Have an Anechoic Chamber? Not every organisation can invest $500K–$2M+ in a purpose-built anechoic facility. Several practical alternatives exist: Sound Intensity Method (ISO 9614) Sound intensity measurements are inherently less sensitive to room reflections because intensity is a vector quantity — it distinguishes between outgoing sound (from the source) and incoming sound (reflections from room surfaces). This allows sound power determination in ordinary rooms without anechoic treatment. Trade-off: Requires specialised intensity probes and more complex measurement procedures. Acoustic Test Boxes For small products (electronics, components, transducers), a desktop-sized acoustic test box provides a controlled, low-noise environment that approximates anechoic conditions within a defined frequency range. These are significantly cheaper than a full chamber and can be placed directly on a production line. CRYSOUND offers a comprehensive range of acoustic test chambers designed for different testing scenarios: CRY723 Pneumatic Acoustic Test Chamber — A compact, shell-type test box ideal for smartphones and wireless wearables. Combine two CRY723 units with a CRY6151B analyzer for complete audio, ENC, and ANC measurements. CRY725 Pneumatic Acoustic Test Chamber — Designed for larger wireless devices such as laptops and walkie-talkies. Compatible with comprehensive testers and vector network analyzers. CRY7865 Pneumatic Acoustic Test Chamber — A high-performance drawer-style chamber with both acoustic isolation and RF shielding, ideal for production line audio and noise measurements of wireless electronic devices. CRY7412 Ultra-Quiet Chamber — An ultra-quiet chamber for testing very quiet sounds in noisy environments. Features a unique double-shell design for superior noise isolation. All models support pneumatic operation for fast, repeatable DUT loading on production lines — a practical alternative when a full anechoic chamber is not justified by the application. Portable Acoustic Arrays Modern acoustic imaging cameras can identify and localise noise sources in situ — in the factory, on the production line, or in the field — without any anechoic treatment. While not a substitute for standards-compliant sound power measurements, acoustic imaging enables rapid noise source diagnosis that previously required dedicated chamber time. The CRY8500 Series SonoCam Pi Acoustic Camera, is a portable acoustic imaging camera that delivers real-time sound source visualisation — ideal for R&D engineers working on noise source identification in automotive NVH, industrial equipment, and consumer electronics. In-Situ Sound Power (ISO 3744 with Corrections) ISO 3744 allows environmental correction factors to account for room reflections. If the correction is small (typically less than 2 dB), the measurement can be performed in a reasonably quiet industrial space without a purpose-built chamber. The SonoDAQ Pro data acquisition system combined with OpenTest software supports automated sound power calculations with environmental corrections built in — enabling standards-compliant measurements without a dedicated anechoic chamber. Frequently Asked Questions How much does an anechoic chamber cost? Costs vary widely based on size, performance requirements, and cut-off frequency. A small hemi-anechoic room for component testing may start around $100K–$300K, while a large automotive-grade full anechoic chamber can exceed $2M. For smaller products, acoustic test boxes offer similar isolation at a fraction of the cost. What is the difference between an anechoic chamber and a soundproof room? A soundproof room blocks external noise from entering but does nothing about internal reflections. An anechoic chamber both blocks external noise and absorbs internal reflections, creating a free-field environment for precision measurement. Can I do acoustic testing without an anechoic chamber? Yes. Depending on your application, alternatives include acoustic test boxes for small products, sound intensity methods (ISO 9614), portable acoustic imaging cameras like the CRY8500 SonoCam Pi, and in-situ measurements with environmental corrections using systems like SonoDAQ Pro. What frequency range does an anechoic chamber cover? The usable frequency range depends on the wedge depth and chamber dimensions. Most chambers are effective from their cut-off frequency (typically 80–200 Hz) up to 20 kHz or beyond. Below the cut-off, the chamber no longer provides adequate absorption. How is an anechoic chamber qualified? Chamber qualification follows ISO 26101, which verifies that the inverse-square law (sound pressure decreasing by 6 dB per doubling of distance) holds within specified tolerances at the measurement positions. Conclusion Anechoic chambers remain the gold standard for precision acoustic measurement — but they are not the only option. Understanding what your application truly requires helps you choose the right solution, whether that is a full anechoic room, a compact acoustic test chamber, or an in-situ measurement approach. At CRYSOUND, we provide the full spectrum: from purpose-built anechoic chambers to portable acoustic test boxes and advanced measurement systems — so you can get accurate results regardless of your facility constraints. Contact us to discuss which solution fits your testing requirements.
During pilot production and production line ramp-up, many issues do not appear in the way teams initially expect. Sometimes it starts with a small fluctuation at a test station, or a comment from a line engineer saying, "This result looks a bit unusual."However, when takt time, yield targets, and delivery milestones are all under pressure, these seemingly minor anomalies can quickly be amplified and begin to affect the overall production rhythm. We have been working with Huaqin as a long-term partner. As projects progressed, the challenges encountered on the production line became increasingly complex. On site, our role gradually extended from basic production test support to problem analysis and cross-team coordination during pilot production. In many cases, the focus was not simply on whether a test station was functioning, but on how to absorb uncertainties early and prevent them from disrupting delivery schedules. The following two experiences both took place during the pilot production phase of Huaqin projects. They are not exceptional cases. On the contrary, they represent the kind of everyday issues that most accurately reflect the realities of production line delivery. Airtightness Testing Issues in Project α During the pilot ramp-up of Project α, the airtightness test station for the audio microphone showed clear instability. For the same batch of products, pass rates fluctuated noticeably across repeated tests, frequently interrupting the station's operating rhythm. Initial troubleshooting naturally focused on the test system itself, including software logic, equipment status, and basic parameter settings. It soon became clear, however, that the issue did not originate from these areas. As on-site verification continued, we gradually confirmed that the anomaly was more closely related to the product's mechanical structure and material characteristics. This model used a relatively uncommon combination of materials. A sealing solution that had worked well in previous projects could not maintain consistency during actual compression. Even slight variations in applied pressure were enough to influence test results. Once the direction of the problem was clarified, the on-site approach shifted accordingly. Rather than repeatedly adjusting the existing solution, we returned to verifying the compatibility between materials and structure. Over the following period, we worked together with the customer's engineering team on the production line, testing multiple material options. This included different types of silicone and cushioning materials, variations in silicone hardness, and adjustments to plug compression methods. Each step was evaluated based on real test results before moving forward. The process was not fast, nor was it particularly clever. In essence, it came down to repeatedly confirming one question: could this solution run stably under real production line conditions?Ultimately, by introducing a customized soft silicone gasket and making fine parameter adjustments, the airtightness test results gradually stabilized. The station was able to run continuously, and the pilot production rhythm was restored. Figure 1. Test Fixture Diagram Noise Floor Issues in Project β Compared with the airtightness issue in Project α, the noise floor anomaly encountered during pilot production in Project β was more complex to diagnose. During headphone pilot production for Project β at Huaqin's Nanchang site, the noise floor test station repeatedly triggered alarms. Test data showed that measured noise levels consistently exceeded specification limits, significantly impacting the pilot production schedule. This model used high-sensitivity drivers along with a new circuit design, making the potential noise sources inherently more complex. It was not a problem that could be resolved by simply adjusting a single parameter. Rather than focusing solely on the test station, we worked with the customer's audio team to investigate the issue from a system-level signal chain perspective. The process involved sequentially testing different shielding cables, adjusting grounding strategies, evaluating various Bluetooth dongle connection methods, and isolating potential power supply and electromagnetic interference sources within the test environment. Through continuous spectrum analysis and comparative testing, the scope of the issue was gradually narrowed. It was ultimately confirmed that the elevated noise floor was primarily related to power interference from the Bluetooth dongle, combined with differences in product behavior across operating states. After this conclusion was reached, relevant configurations were adjusted and validated on site. As a result, noise floor measurements returned to a stable and controllable range, allowing pilot production to proceed. Figure 2. Work with the customer engineer to solve problems Common Characteristics of Pilot Production Issues Looking back at these two pilot production experiences, it becomes clear that despite their different manifestations, the underlying diagnostic processes were quite similar. Whether dealing with airtightness instability or excessive noise, the root cause could not be isolated to a single module. Effective resolution required on-site evaluation across mechanical structure, materials, system operating states, and test conditions. During pilot production, issues of this nature rarely come with ready-made answers. They are also unlikely to be resolved through a single verification cycle. More often, progress is made through repeated trials, comparisons, and eliminations, gradually converging on a solution that is genuinely suitable for long-term production line operation. Production line delivery rarely follows a perfectly smooth path. In many cases, what ultimately determines whether a project can move forward as planned are those unexpected issues that must be addressed immediately when they arise. In our long-term collaboration with customers, our work often takes place at these critical moments—working alongside engineering teams to stabilize processes, maintain momentum, and keep projects moving forward step by step. If you also want CRYSOUND to support your production line, you can fill out the Get in Touch form below.
In our previous blog post, "Abnormal Noise Detection: From Human Ears to AI"we discussed the key pain points of manual listening, introduced CRYSOUND's AI-based abnormal-noise testing solution, outlined the training approach at a high level, and showed how the system can be deployed on a TWS production line. In this post, we take the next step: we'll dive deeper into the analysis principles behind CRYSOUND's AI abnormal-noise algorithm, share practical test setups and real-world performance, and wrap up with a complete configuration checklist you can use to plan or validate your own deployment. Challenges Of Detecting Anomalies With Conventional Algorithms In real factories, true defects are both rare and highly diverse, which makes it difficult to collect a comprehensive library of abnormal sound patterns for supervised training. Even well-tuned—sometimes highly customized—rule-based algorithms rarely cover every abnormal signature. New defect modes, subtle variations, and shifting production conditions can fall outside predefined thresholds or feature templates, leading to missed detections (escapes). In the figure below, we compare two wav files that we generated manually. Figure 1: OK Wav Figure 2: NG Wav You can see that conventional checks—frequency response, THD, and a typical rub & buzz (R&B) algorithm—can hardly detect the injected low-level noise defect; the overall curve difference is only ~0.1 dB. In a simple FFT comparison, the two wav files do show some discrepancy, but in real production conditions the defect energy may be even lower, making it very likely to fall below fixed thresholds and slip through. By contrast, in the time–frequency representation , the abnormal signature is clearly visible, because it appears as a structured pattern over time rather than a small change in a single averaged curve. Figure 3: Analysis results Principle Of AI Abnormal Noise Algorithm CRYSOUND proposes an abnormal-noise detection approach built on a deep-learning framework that identifies defects by reconstructing the spectrogram and measuring what cannot be well reconstructed. This breaks through key limitations of traditional rule-based methods and, at the principle level, enables broader and more systematic defect coverage—especially for subtle, diverse, and previously unseen abnormal signatures. The figure below illustrates the core workflow behind our training and inference pipeline. Figure 4: Algorithm Flow Principle During model training, we build the algorithm following the workflow below. Figure 5: Algorithm Judgment Principle How To Use And Deploy The AI Algorithm Preparation First, prepare a Low-Noise Measurement Microphone / Low-noise Ear Simulator and a Microphone Power Supply to ensure you can capture subtle abnormal signatures while providing stable power to the mic. Figure 6: Low-Noise Measurement Microphone Next, you'll need a sound card to record the signal and upload the data to the host PC. Figure 7: Data Acquisition System Third, use a fixture or positioning jig to hold the product so that placement is repeatable and every recording is taken under consistent conditions. Finally, ensure a quiet and stable acoustic environment: in a lab, an anechoic chamber is ideal; on a production line, a sound-insulation box is typically used to control ambient noise and keep measurements consistent. Figure 8: Anechoic Room Figure 9: Anechoic Chamber Model Development First, create a test sequence in SonoLab, select "Deep Learning" and apply the setting. Next, select the appropriate AI abnormal-noise algorithm module and its corresponding API Figure 10: Sequence Interface 1 Then open Settings and specify the model type, as well as the file paths for the training dataset and test dataset. Click Train and wait for the model to finish training (Training time depends on your PC's hardware) Figure 11: Sequence Interface 2 During training, the status indicator turns yellow. Once training is complete, it switches to green and shows a "Training completed" message. Figure 12: Sequence Interface 3 Finally, place your test WAV files in the specified test folder and run the sequence. The model will start automatically and output the analysis results. Test Case Figure 13:Test Environment Figure 14:Test Curve System Block Diagram Figure 15: System Block Diagram 1 Figure 16: System Block Diagram 2 Equipment More technical details are available upon request—please use the "Get in touch" form below. Our team can share recommended settings and an on-site workflow tailored to your production conditions.
