What's the matter with the multimeter nF and uF jumping back and forth
The measured capacitance of the capacitor is just around the node where it is not so convenient to use these two different capacitance units to identify. In fact, at this time, the multimeter is just like a human being, unable to make up its mind. Especially when the capacitance of the capacitor you are testing plus the distributed capacitance of the multimeter pen of a few pF or more than ten pF (including the distributed capacitance of the human body holding the multimeter pen) will just change the node where the capacitance unit is used. , this phenomenon is more likely to occur.
The range of the multimeter is too wide from 1uF-999kF (different multimeters have different ranges, according to the actual situation, this time we are talking about a large-range universal multimeter), so there is an error, and in this way uF.nF and F , The beating between uF and nF can be ignored.
Take thermometers as an example, industrial thermometers and human mercury thermometers, the error of 0.01-0.1 degrees can be ignored when industrial thermometers measure hundreds of thousands of temperatures.
What is the reason why the needle of the multimeter measures the DC current in the opposite direction?
1. Function of pointer multimeter
In fact, the pointer multimeter is the same as other multi-function meters, which can measure DC current, DC voltage, AC current, AC voltage, resistance and other data.
2. How to realize the measurement of direct current
The head of the pointer multimeter is actually a head of a DC ammeter. When it is necessary to measure the DC current, each gear is equivalent to connecting a resistor with a different resistance in parallel to the head, so as to divide the current. When measuring DC voltage, a resistor of different resistance is connected in series with the meter head to reduce the voltage.
How to measure with a multimeter
Using a multimeter can be divided into several steps:
1. Observation and mechanical zero adjustment are required before use, that is, to ensure that the pointer is on the zero scale before use.
2. Select the correct gear according to the measured data. For example, when measuring DC current, the gear is selected as DCmA. Here, the DC gear must be selected, because DC is direct current and AC is alternating current. The specific gear needs to be estimated according to the actual measurement data. value.
3. The red test lead should be inserted in the "+" position, and the black test lead should be inserted in the "com" port. When measuring, the red test lead should be at the positive pole of the device under test, and the black test lead should be at the negative pole of the device under test (here is the focus of this question )
Because the characteristic of direct current is that the direction does not change with time, it has a direction, and the direction must be paid attention to when measuring. If measured as shown above, the reverse value will be displayed.
