Designing a Low-Cost ECG Sensor and Monitor: Practical Considerations and Measures
Daniel Tze Huei Lai, Rezaul Begg, Marimuthu Palaniswami in Healthcare Sensor Networks, 2016
An automatic gain control (AGC) is a control system which uses negative feedback to stabilize the gain of the ECG amplifier in much the same way a phase-locked loop (PLL) stabilizes and locks signal frequencies. An AGC system, like the PLL, is highly nonlinear and complex to analyse. Again like the PLL, the AGC system can be approximated to the first order with a considerable amount of inaccuracy. An AGC system is not the same as a limiter, which does not usually use any form of feedback and merely crops the output waveform so that the required output level is maintained. An AGC system has to maintain the required output level without any form of distortion. An AGC is highly desirable in an ECG system, as smaller ECG signals can be automatically increased and larger ones decreased to the same output level without any adjustment by the user being necessary. This is particularly important when the ECG system is to be used on many patients in quick succession.
Quality Assurance, Elimination of Artifacts, and Repeatability
Noam Gavriely, David W. Cugell in Breath Sounds Methodology, 2019
Visual monitoring of breath sounds amplitude is available by observing the signal on an oscilloscope screen or on a computer monitor. Adequate adjustment of the signal amplitude (gain) is important: the amplifier gain should be adjusted to take advantage of the full dynamic range of the amplifier and A/D converter, but should never exceed the amplifier or the converter limits and saturate the system. This type of quality control is better done visually, because the ear is not very good at detecting amplifier saturation. For certain applications, such as long-term monitoring of breath sounds, an alarm or automated gain adjustment, with an automatic gain control device, is useful to minimize system under- or overloading. A disadvantage of automatic gain control amplifiers is that they do not provide information on the instantaneous gain and prevent standardization of the measurement of breath sound amplitude. Improved dynamic range of the analog amplifiers and filters, and a higher-resolution A/D converter (i.e., 16-bit A/D) will minimize these problems.
A Biomorphic Active Cochlear Model In Silico
Iniewski Krzysztof in Integrated Microsystems, 2017
Here we present frequency responses measured from linearly spaced BM segments and longitudinal responses to octave-spaced pure tones, both at an input level of 24 dB. We also present frequency responses obtained at various input intensities (0–48 dB), demonstrating automatic gain control. We then demonstrate the role of ABC by disabling it. Finally, we present the chip’s real-time responses to a chirp-click sound sequence.
Signal processing & audio processors
Published in Acta Oto-Laryngologica, 2021
Anandhan Dhanasingh, Ingeborg Hochmair
Automatic Sound Management (ASM) is a term created to bring together a set of front-end features that were implemented in the audio processors at various time points at MED-EL. Automatic Gain Control (AGC) is one of the features within ASM that attenuates high-level signal and enhances low-level signal, enabling the CI user to hear even a very soft sound signal. AGC recreates or models the sound level compression function of the basilar membrane and compresses the range of sound levels by mapping a dynamic input range of 75 dB to a narrower output dynamic range. This feature is available in all MED-EL audio processors, including in off-the-ear processors, existent since 2013. AGC is the first-ever and the only front-end feature that was implemented in MED-EL’s COMBI 40 body-worn audio processor and is still available along with other advanced features in the latest SONNET2 BTE audio processor. The modern AGC in CI audio processor carries a dual time constant compression system (slow and fast detector). The slow detector is generally in control of the system gain and mainly determines the dynamic properties of the AGC. The exceptions are sudden intense transient sounds (like door slamming) when the AGC gain is determined by the fast detector, which immediately reduces the system gain.
Screening of serum biomarkers of preeclampsia by proteomics combination with bioinformatics
Published in Hypertension in Pregnancy, 2019
Yuee Ling, Jie Su, Jie Lin, Sumei Wang
The peptides were ionized in an NSI ion source and analyzed by tandem mass spectrometry (MS) using Q ExactiveTM Plus (Thermo) coupled online to the ultra performance liquid chromatography (UPLC). The ion source voltage was set to 2.0 kV, and high resolution Orbitrap was used to detect and analyze peptide precursor ions and secondary fragments. The scanning range of the first-order mass spectrum was set to 350–1800 m/z, and the scanning resolution to 70,000. The fixed starting point of the second-order mass spectrum scanning range was 100 m/z, and the scanning resolution was set to 17,500. The data were acquired using the data-dependent scanning (DDA) program, alternating between one MS scan followed by 20 MS/MS scans with 15 s dynamic exclusion. Automatic gain control (AGC) was set at 5E4 in order to improve the efficiency of MS.
Proteomic global proteins analysis in blast lung injury reveals the altered characteristics of crucial proteins in response to oxidative stress, oxidation-reduction process and lipid metabolic process
Published in Experimental Lung Research, 2022
Peifang Cong, Changci Tong, Shun Mao, Xiuyun Shi, Ying Liu, Lin Shi, Hongxu Jin, Yunen Liu, Mingxiao Hou
The tryptic peptides were dissolved in.1% formic acid (solvent A) and directly loaded onto a homemade reversed-phase analytical column (15-cm length, 75 µm i.d.). The gradient was comprised of an increase from 6 to 23% solvent B (0.1% formic acid in 98% acetonitrile) over 26 min, 23–35% in 8 min, increasing to 80% in 3 min, and then holding at 80% for the last 3 min, all at a constant flow rate of 400 nl/min on an EASY-nLC 1,000 UPLC system (Thermo Scientific, United States). The peptides were subjected to an NSI source. Then, MS/MS in Q ExactiveTM Plus (Thermo Fisher Scientific, Waltham, MA, United States) coupled online to the UPLC was performed. The electrospray voltage applied was 2 kV. The m/z scan range was 350 to 1,800 for a full scan, and intact peptides were detected in the Orbitrap at a resolution of 70,000. Peptides were then selected for MS/MS using the NCE setting as 28, and fragments were detected in the Orbitrap at a resolution of 17,500. A data-dependent procedure that alternated between 1 MS scan followed by 20 MS/MS scans with 15 s dynamic exclusion. Automatic gain control (AGC) was set at 5E4. The fixed first mass was set at 100 m/z.
Related Knowledge Centers
- Auditory System
- Photoreceptor Cell
- Retina
- Visual System
- Signal-to-Noise Ratio
- Distortion
- Peak Meter
- Active Noise Control