A multi-channel meridian impedance detector used to the 3D meridian visualization positioning is presented. The detector is designed with the four-electrode method based on current driving according to low impedance of the meridian. The detector consists of power-supply module, sinusoidal signal generator, voltage-controlled current source, isolation amplifiers, filter circuit, amplitude detectors and so on.
Amplifiers, Electronic ; Electric Impedance ; Electrodes ; Meridians

To fit the technological requirements in electrical impedance tomography system, an improved bipolar optocoupler isolation amplifier based on single analog optocoupler was realized. The experimental results illustrates that the full power -3dB bandwidth of this circuit is greater than 800 KHz, the equivalent output noise is lower than 50 uV(RMS), and the linearity at +/- 4 V inputs is lower than 0.01%. In addition to these features, the circuit also have the advantages of simple structure and no distortion caused by mismatch between analog optocouplers.
Amplifiers, Electronic ; Electric Impedance ; Equipment Design ; Humans ; Tomography ; instrumentation

Distortion will occur when testing medical microwave products, due to its high power, high frequency, in the existing radiated emission testing process which will cause saturation non-linear of the pre-amplifier. It will lead to test distorted, the test results are not accurate. This article will improve the original test method by adding some suppressing-frequency devices to suppress the main frequency energy and avoid pre-amplifier saturation, eliminate distortion. All of this will ensure the test results are effective and relia ble.
Amplifiers, Electronic ; Equipment Design ; Equipment and Supplies ; Materials Testing ; Microwaves

An intravascular ultrasound-enhanced thrombolysis excitation system with adjustable frequency, amplitude and duty cycle was designed based on FPGA (ZYNQ-7Z020). Firstly, the FPGA generated waveform amplitude binary data based on direct digital frequency synthesis (DDS) technology, and then the data was converted into burst signal through an external daughter card, which included D/A conversion circuit, active low-pass filter, power amplifier circuit and impedance matching circuit. The test results demonstrated that the output waveform reached the target with advantages of simple implementation and flexible control, the peak negative pressure generated from ultrasound transducer was doubled by means of an electrical impedance matching network. In vitro thrombus models were applied to verify the excitation system, it turned out that ultrasound cavitation effect generated could accelerate the penetration of urokinase and increase the thrombolysis rate by about 20%.
Amplifiers, Electronic ; Electric Impedance ; Thrombolytic Therapy ; Ultrasonography ; Ultrasonography, Interventional

A wireless transmission system for visual prosthesis is introduced. Power and data are transmitted through inductive link between only one pair of coils, in order to reduce the size of the device. The transmitter is based on Class-E power amplifier due to its high efficiency, and a modulation circuit is added to control the dc supply of the Class-E amplifier to achieve ASK modulation of data with modulation depth of 25%. In addition, an experimental system is implemented, and test shows that it sufficiently supports a 16-channel micro-stimulator on power delivery and data transfer rate.
Amplifiers, Electronic ; Automatic Data Processing ; Electric Power Supplies ; Electronics, Medical ; Prosthesis Design ; Telemetry ; Visual Prosthesis

AIM AND METHODSUsing blind whole-cell recording techniques on rat hippocampal slices, the function and mechanisms of several leak subtraction methods of Axon patch clamp system (Axopatch amplifier and pClamp software) were analyzed. That how to select and use scaled P/N leak subtraction, patch clamp amplifier leak subtraction and Clampfit leak subtraction were emphasized in our present study.

RESULTSThe noise induced by scaled P/N leak subtraction of Clampex soft ware was smaller than that of P/N leak subtraction. Axon patch clamp amplifier leak subtraction could subtract the leak current produced by single depolarizing pulse but not the leak current produced by a series of different step depolarizing pulses. Due to its assumption that leak current would be produced if only potential difference arises across membrane, Clampfit leak subtraction was not suitable to subtracting the steady-state leak current while recording voltage-gated channel currents.

CONCLUSIONP/N- and scaled P/N leak subtraction, but not Clampfit leak subtraction, cad be used to subtract steady-state leak current while recording voltage-gated channel currents.

Amplifiers, Electronic ; Animals ; Hippocampus ; physiology ; Male ; Patch-Clamp Techniques ; methods ; Rats ; Rats, Wistar ; Software

AIMTo study the effects of the 50 Hz-filter circuit in a microelectrode amplifier on cardiac action potential waveform and parameters.

METHODSCardiac action potential signals were fed into a microcomputer through a glass microelectrode, a microelectrode amplifier, a differentiator and A/D converter. The cardiac action potential signals were recorded and analyzed with 50 Hz-filter circuit and without it, and the frequency spectrum in the signals was analyzed with the fast Fourier transformation.

RESULTSWhen the 50 Hz-filter circuit was used, the phase 0 of the potential waveform was seriously distorted and prolonged. The maximal rate of depolarization at the phase 0 was cut down, while the other parameters were not effected.

CONCLUSIONThere has already been much 50 Hz element in the action potential waveform. During amplifying the cardiac action potential signal, the 50 Hz-filter circuit should not be turned on. Otherwise, the experiment results will be effected.

Action Potentials ; physiology ; Amplifiers, Electronic ; Animals ; Guinea Pigs ; Myocytes, Cardiac ; physiology ; Papillary Muscles ; cytology ; physiology

The amplifier is easy to saturation because of polarization voltage in ambulatory ECG acquisition. The traditional way is using analog high-pass filter to eliminate, but the output tends to have a residue. If upgrading high-pass filter cutoff frequency, it will lead to low frequency distortion of ECG signals. In this paper, a Savitzky-Golay (SG) smoothing filter has been designed by combining the single edge point and the polynomial order , which can fit the polarization voltage components of ECG signals, filter useful components and get drift-free ECG signals by using the subtraction algorithm. The results of ECG filtering experiment verify the feasibility of the SG smoothing filter, and show the filtered ECG signal without any losses of useful components.
Algorithms ; Amplifiers, Electronic ; Electrocardiography, Ambulatory ; methods ; Humans ; Signal Processing, Computer-Assisted

Skin-hearing aid is a new type of electronic product, which can improve hearing for deaf patients. It is different from audiphones and cochlear implant. The instrument makes use of the effect of the skin response to audio signals. The working process of the instrument is as following. Firstly, the sound signal is converted to audio signal by microphone, then through the power amplifier and booster. Then the signal is transmitted to the brain via skin by electrodes. And finally the hearing is formed. As skin-hearing aid transmits signals through the skin by the electrodes, the intensity of the skin resistance becomes the main factor influencing the response of the skin to audio signal. Skin resistance depends mainly upon the stratum corneum. This article aims to discuss the factors affecting the skin resistance, such as the thickness of the stratum corneum, hydration level of stratum corneum, the relation of audio frequency and skin resistance, and the skin resistance of acupuncture points.
Amplifiers, Electronic ; Equipment Design ; Galvanic Skin Response ; physiology ; Hearing Loss, Sensorineural ; etiology ; rehabilitation ; Humans ; Skin Physiological Phenomena

Induced current electrical impedance tomography (ICEIT) is a new branch of electrical impedance tomography (EIT). We have designed and set up a high accuracy ICEIT hardware system with 32 electrodes based on physical phantom, and we have brought forward a new method to reduce the additive electromotive force (EMF) in circuit of the electrode leads. By use of the technique of twisted pair wire, the additive EMF in the circuit of the electrode leads has been reduced to 10% of that before use and the precision of the system has been improved. The precision of the final results is better than 0.5% after 1000 measurement data averaged. Applying the reconstructive algorithm, we have obtained preliminary images based on physical phantom.
Algorithms ; Amplifiers, Electronic ; Electric Impedance ; Electrodes ; Electromagnetic Phenomena ; Equipment Design ; Models, Theoretical ; Signal Processing, Computer-Assisted ; instrumentation ; Tomography ; methods