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Why does the orifice plate flowmeter produce errors
2011-10-28 15:17:50

检测 用测电限的方法来测量低电压的倍率量程,实际值与测得结果符合;准确度级别较高的分压箱,高电压的倍率量程,来测电阻就会产生较大的误差。 Orifice flowmeter detection , using the method of measuring the limit of electricity to measure the low-voltage rate range, the actual value is consistent with the measured result; a voltage divider with a higher accuracy level, and the high-voltage rate range will produce resistance Large error.

:⑴ . 电阻法 We test the voltage division box, and generally check the voltage division ratio. There are two methods : 电阻 . Resistance method . 电压法。 . Voltage method.

The measurement of voltage is actually the measurement of resistance. We know the resistance level, then I can get the voltage division ratio. This is the resistance method.

It is known from the working principle of the voltage divider that the ratio of voltage is equal to the ratio of electrical limit.

误差,我们分析了三个原因: Orifice flowmeter errors, we analyzed three reasons:

First of all

Leakage is one of the reasons affecting the voltage division ratio:

      Temperature and humidity in the air

      Dust impurities

These two factors are the factors that affect the insulation resistance. They are often the cause of the leakage of the circuit and the case.

Secondly

During the process of measuring the resistance, the measured working current is much smaller than the actual current, so the voltage divider in actual use is more likely than the test current. Because the voltage of each section of the voltage division box is not the same, the leakage currents formed may also be different. They are the reasons that directly affect the accuracy of the voltage division ratio.

   At last

The "degree" that also affects the voltage division ratio should not be underestimated:

      Function of degree

      Change in degree

For example, let's take the effect of temperature on the partial pressure ratio; there are two kinds of effects that are verified: First, the effect of the temperature of the partial pressure box itself under abnormal working conditions; When we measure the resistance of the voltage divider, we only need to consider the verification device used in measuring the resistance of the voltage divider; we do not need to consider the rated current passed by the voltage divider. Therefore, at the time of inspection, the normal current of the resistance of the voltage box is much smaller than the rated current.

For example, we say from the verification time; the normal use time is shorter than the actual use time, so there is a large error in the verification process and in actual use.

In addition, the resistance value of each section is different, and care must be taken in the selection of wire and temperature coefficient to avoid errors in the measurement process. Orifice flowmeter