The slope of the scale characteristic curve. Therefore, range migration means a change in sensitivity; and if it is only a zero point shift, the sensitivity is unchanged.
Expressed by the definition of sensitivity, the sensitivity is essentially equivalent to the magnification of the meter, just because [, and y have specific dimensions, so the sensitivity is also dimensioned and determined by y; and the magnification has no dimension. So the meaning of sensitivity is greater than the magnification
It is much broader. Often confused with meter sensitivity is the meter resolution. It is the minimum input that the meter output can respond to and resolve, also known as the meter sensitivity limit. Resolution is a reflection of sensitivity. Generally speaking, the sensitivity of the meter is high, and the resolution is the same.
Also high. Therefore, in practice, it is mainly desirable to improve the sensitivity of the meter to ensure a better resolution.
Sensitivity is transferable in a measurement or control system consisting of multiple meters. For example, the instrument system in series with the head and tail (that is, the output of the previous meter is the input of the latter meter), and the total sensitivity is the product of the sensitivity of each meter.
The measured value displayed by the meter indicating device is called the indication value, which is a reflection of the measured true value. Strictly speaking, the measured true value is only a theoretical value, because there is an error in the value measured regardless of the instrument. In practice, it will often be measured with a meter of appropriate accuracy or
The contracted truth value determined by a specific method replaces the true value. For example, a standard instrument that has been calibrated by a national standard metrology institute is used for measurement, and the measured value can be used as the agreed true value.
The difference between the indication value and the accepted agreement true value is called the absolute error, that is, the absolute error can usually be referred to as the error. When the error is positive, it indicates that the indication value of the meter is too large, and vice versa.
The ratio of the absolute error to the agreed true value is called the relative error, and is usually expressed as a percentage, that is, relative error (%) - absolute error / agreed true value
Although it is reasonable to measure the accuracy of the instrument by the absolute error as a percentage of the agreed true value, the meter is mostly used to measure the amount close to the upper limit value. Therefore, the agreed true value in the range substitution method is used to obtain the reference error, considering the entire range. The biggest inside
For the ratio of the error to the range, the maximum reference error of the instrument is independent of the specific indication of the meter, which can better explain the accuracy of the meter measurement. It is the main form of the basic error of the instrument and one of the main quality indicators of the instrument.
The instrument shall specify the allowable value of the reference error when it leaves the factory, which is referred to as the allowable error. If the tolerance of the meter is recorded as Q, the maximum reference error is recorded as Q. . . , then the following relationship is satisfied between the two
Any measurement is related to environmental conditions, including ambient temperature, relative humidity, supply voltage, and installation. When the instrument is applied, it should be measured strictly according to the specified environmental conditions, that is, the reference working conditions. The error obtained at this time is called
Basic error. Therefore, if the measurement is performed under non-reference working conditions, the error obtained at this time includes an additional error, which is also called an additional error, in addition to the basic error.
The above discussion is basically for the static error of the instrument. The static error refers to the error when the instrument is in a static state, or the error that is presented when the measured change is very slow. At this time, the inertia factor of the instrument is not considered. There are also dynamic errors in the meter, and the dynamic error is
Refers to the additional error caused by the inertia delay of the instrument, or the error during the change process. The application of instrument static errors is more common.
Any instrument has a certain error. Therefore, when using the meter, you must first know the accuracy of the meter, in order to estimate the difference between the measured result and the agreed true value, that is, the estimated value of the measured value. The accuracy of the meter is usually determined by the maximum allowable reference error.
The number after the percent sign is measured.
The process of determining the accuracy level of the meter. For ease of observation and understanding, the deviations have been consciously magnified. The straight line OA in the figure is an ideal input output characteristic curve, and the broken lines 3 and 4 are the lower and upper limits of the basic error. Obtained during the verification or verification process
The actual characteristic curves obtained are recorded as curves 1 and 2, where curve 1 is obtained when the input value gradually increases from the lower limit value to the upper limit value, and is called the actual rise curve; and curve 2 is the input value from the upper limit value to What is obtained when the lower limit value is gradually decreased is called the actual drop curve.
The maximum actual positive and negative deviations can be obtained from the deviations of curves 1 and 2 from line 0A, respectively. The actual rising curve and the actual falling curve obtained by the instrument inspection often appear to be non-coincident, so that the characteristic curve of the meter forms a ring shape. This phenomenon is called
Hysteresis. Obviously, when hysteresis occurs, the same input value of the meter often corresponds to multiple output values, and an error occurs.
There are three situations in the information interface between the automatic detection or automatic control system and the external environment: the sensor that acquires the state of the detection object, and the actuator that controls and adjusts the state of the object; the interface between the operator and the instrument device; the monitoring instrument
Information exchange with other systems. The sensor is the input port of all the information of the measured object, and is the central component of signal detection and signal conversion; the signal conversion or the electrical signal conversion may not be required between the interface of the monitoring system and other systems.
However, signal detection or signal conversion of the monitoring object and the monitoring system is very important.
