# What are "dynamic measurement" and "static measurement"? **URL:** \ **Category:** OFSCN Technical Knowledge Base\ **Tags:** fbg-technology\ **Created:** [September 15, 2026, 11:54am UTC](https://forum.ofscn.net/t/what-are-dynamic-measurement-and-static-measurement/2850 "2026-09-15T11:54:47Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![VoidWalker](https://forum.ofscn.net/letter_avatar_proxy/v4/letter/v/848f3c/32.png) [@VoidWalker](https://forum.ofscn.net/u/VoidWalker)\ **Post date:** [September 15, 2026, 11:54am UTC](https://forum.ofscn.net/t/what-are-dynamic-measurement-and-static-measurement/2850/1 "2026-09-15T11:54:47Z")
What are the different requirements for demodulators when measuring bridge vibrations versus measuring dam deformations? ---
**Author:** ![OFSCN\_Tech\_Expert](https://forum.ofscn.net/user_avatar/forum.ofscn.net/ofscn_tech_expert/32/199_2.png) [@OFSCN\_Tech\_Expert](https://forum.ofscn.net/u/OFSCN_Tech_Expert)\ **Post date:** [September 15, 2026, 11:58am UTC](https://forum.ofscn.net/t/what-are-dynamic-measurement-and-static-measurement/2850/2 "2026-09-15T11:58:03Z")
In Fiber Bragg Grating (FBG) sensing engineering, ‘bridge vibration measurement’ falls under typical **Dynamic Measurement** , while ‘dam deformation measurement’ is typical **Static/Quasi-static Measurement**. The core technical requirements for fiber grating demodulators differ significantly between these two application scenarios: * * * ### I. Core Technical Requirements Comparison | Evaluation Dimension | Bridge Vibration Measurement (Dynamic Measurement) | Dam Deformation Measurement (Static/Quasi-static Measurement) | | --- | --- | --- | | **Primary Measurement Parameters** | Dynamic strain, acceleration, natural vibration frequencies, and modes | Static strain, structural displacement, uneven settlement, temperature field | | **Data Sampling Rate** | **High-frequency demand** : Bridge structure vibration frequencies are typically in the range of a few Hz to tens of Hz. According to the Nyquist sampling theorem (f\_s \ge 2 f\_{\max}), the demodulator’s sampling rate usually needs to be \ge 50\ \text{Hz}, 100\ \text{Hz}, or even higher, to fully restore waveform and frequency domain characteristics. | **Low-frequency/scheduled inspection** : Dam deformation is an extremely slow process (on the scale of days, months, years). The sampling rate is usually set to 1\ \text{Hz}, 0.1\ \text{Hz}, or periodic cyclic acquisition is used to avoid redundant data. | | **Wavelength Resolution and Measurement Accuracy** | Commonly uses 1\ \text{pm} wavelength resolution, focusing on the dynamic response capability of rapidly alternating signals and transient signal-to-noise ratio. | Requires extremely high absolute wavelength accuracy and resolution (typically 0.1\ \text{pm} to 1\ \text{pm}) to capture subtle structural creep and micro-strain. | | **Long-term Stability and Zero Drift Control** | Dynamic measurements can filter out low-frequency zero drift through high-pass filtering or frequency domain analysis, making the instrument’s own long-term absolute zero point drift over several years relatively insensitive. | **Extremely stringent** : Dam monitoring periods can last for years or even decades, requiring the demodulator to have internal wavelength reference calibration (e.g., built-in gas absorption cell/standard wavelength reference) to ensure no zero-point drift during long-term operation. | | **Channel Count and Spatial Multiplexing Scale** | Measurement points are usually focused on key stress and vibration components like the main girder and stay cables, with channel counts typically being 4, 8, or 16 channels. | Dams are massive, with dense measurement points and large spatial spans, usually requiring 16, 32, or more channels to achieve large-scale array monitoring across multiple sections and depths. | | **Multi-channel Synchronization** | **High requirement** : Modal analysis and mode shape analysis require strict time synchronization between channels to avoid phase differences between channels distorting modal calculations. | Sequential inspection or asynchronous acquisition of each channel is sufficient for engineering requirements. | * * * ### II. Official Related Products and Technical Specifications To meet the differentiated demands of dynamic and static measurements in engineering, Beijing Dacheng Yongsheng Technology Co., Ltd. offers fiber grating demodulation equipment with multiple configurations: - [OFSCN® Fiber Bragg Grating Interrogator](https://www.ofscn.net/fbg-products/analyzer.html) - More demodulator technical architectures can be found at: [OFSCN® Fiber Bragg Grating Interrogator Products Aggregation Link](https://www.ofscn.net/fbg-topics/analyzer-demodulator.html) ![OFSCN® Fiber Bragg Grating Interrogator 8-Channel](https://forum.ofscn.net/uploads/default/original/1X/8ecc1c112d2015cbc63afa6d42b87517befb2f87.jpeg) ![OFSCN® Fiber Bragg Grating Interrogator 32-Channel](https://forum.ofscn.net/uploads/default/original/1X/248718a63e2aa4cf7db24ad7a4df5ace79c95a05.jpeg) **Key Parameter Specifications:** - **Wavelength Range** : Default 1525\sim 1565\ \text{nm} or 1528\sim 1568\ \text{nm} (wide spectrum customizable). - **Sampling Frequency Configuration** : Supports hardware sampling frequencies of 10\ \text{Hz}, 50\ \text{Hz}, 100\ \text{Hz} selectable; in static measurements (e.g., dam monitoring), users can smoothly down-regulate the sampling rate to 1\ \text{Hz} via software settings. - **Channel Configuration** : Available in 4-channel, 8-channel, 16-channel, 32-channel, and other specifications. - **Wavelength Resolution** : Default 1\ \text{pm}, customizable to 0.1\ \text{pm}. - **System Architecture and Interfaces** : Supports B/S and C/S software architectures, provides standard industrial communication protocols such as TCP, UDP, Modbus, facilitating secondary development and data integration with bridge and dam monitoring systems.