Free time to sort out some of the basic concepts of the following medical instrument parameters, more suitable for beginners to understand some of the more vague concepts of the main technical characteristics and classification of medical instruments:
This article refers to the address: http://
1. Accuracy (accuracy): A measure of the error of an instrument's measurement system. The higher the accuracy of the instrument, the smaller the deviation between its measured value and the theoretical value.
2, precision: the ratio of the maximum deviation between repeated measurements under the same conditions and the full scale of the instrument
3. Sensitivity: Sensitivity refers to the ratio of the output change and the input change in the steady state of the instrument.
Characteristics of medical instruments:
Noise characteristics, personality differences and systemicity, naturalness of physiological functions, diversity of operation and safety of contact interfaces.
Design principles for medical instruments:
Signal factors, environmental factors, medical factors, economic factors, and epoch factors.
Three conditions for medical instruments to form interference:
Interference source, coupling channel, sensitive circuit
Several measures to suppress interference
1) Reasonable grounding
a Safety ground (protective ground)
Power grounding protection grounding equipotential grounding b working grounding
One point grounding (series/parallel) multi-point grounding c sensitive circuit grounding
2) Adopt shielding
General nature of noise
The noise voltage or current is random. The random process of noise cannot be described by a certain time function, but it obeys the statistical law and can be described by the statistical average. The noise voltage can be known by the probability density of the noise process. The probability of falling within a certain range.
The main types of noise in biomedical measurement systems:
1, 1 / f noise: low frequency noise, is the main obstacle in the process of biological signal extraction.
2, thermal noise: is caused by the random thermal motion of the carriers in the conductor.
3, shot noise: is the randomness of the generation and disappearance of carriers in the semiconductor device, so that the number of flowing carriers fluctuates, causing the instantaneous fluctuation of the current caused by the current. . .
Basic requirements for bioelectric preamplifiers:
1) High input impedance:
a) The bioelectric signal source itself is a weak signal with high internal resistance, which exhibits unstable high internal resistance properties through electrode extraction.
b) The internal resistance of the signal source connected to the input of the amplifier is up to 100k Ω, and the input impedance of the amplifier should be at least greater than 1M.
C) If the ratio of the internal resistance of the signal source to the input impedance of the amplifier is 1/100, the distortion and error can be reduced to negligible.
2) High gain:
Bioelectric signal amplitude is small
3) High common mode rejection ratio (large CMRR value):
In order to suppress the interference signal carried by the human body, the differential amplification mode is selected, and the higher the CMRR value, the stronger the interference suppression capability. `F
4) Low noise: The low noise performance mainly depends on the pre-stage, the gain of the amplifier is correctly distributed, etc., and good low noise performance can be obtained.
5) Low drift: Most of the bioelectric signals are low frequency signals, and the baseline drift has a serious impact on the measurement. Low drift performance can be achieved by using a differential input circuit and setting a zero-return circuit.
6) Set the protection circuit: the front-end setting should include the human body safety protection circuit and the amplifier input protection circuit.
7) Set the fast calibration circuit: to indicate the amplitude of the signal under test in time
Fiber Optic Splice Closure,Fiber Optic Splice Case,Fiber Splice Closures,Outdoor Fiber Optic Splice Closure
Cixi Dani Plastic Products Co.,Ltd , https://www.cxdani.com