GND( ground) resistor value measured by a multimeter

In ATX power maintenance, it is often necessary to use a multimeter; to measure the ground resistor of the test points.            

For ac high voltage input side: select the diode block of the multimeter; connect the red pen to the negative pole of the whole bridge, and test the test points of the black pen. At this point, the multimeter; will have a reading known in this article as the "ground resistor value on the high voltage side of the ATX power supply. For the dc low voltage output side: select the multimeter; diode block, red pen connection output terminal ground, black pen contact point. At this point, the multimeter; will also have a reading, which in this book is referred to as the "ground resistor value on the low voltage side of the ATX power supply.

In a word, according to the selected reference point, the ground resistor value of ATX power supply is defined as "ground resistor value of high voltage side and ground resistor value of low voltage side".      

Since the ground resistor value can be used as the basis for maintenance, it means that the ground resistor value must reflect a certain essential concurrent of the test point in the circuit, and the 'of whether this essential property is normal or not can effectively clarify the point of failure.       

Not. Strictly speaking, the earth resistor value is essentially the equivalent internal resistor of the circuit network between the "negative pole" or "ground" and the "test points" of the circuit board.            

Real circuits are network like, and there are many nodes on the network. According to the venin’s theorem in electricity, a two - terminal network in each network can be equivalent to a resistor (internal resistor), regardless of its internal structure. The two ends of the equivalent resistor are the two ends of the sub network. When a multimeter; is used to measure the earth resistor of the two-terminal network, the value represents the "equivalent resistor".            

First, whether or not there is a resistor value to the ground reflects whether the line has been connected normally. In general, the current must be able to flow back to the main board from the test scores, otherwise there will be a break. Therefore, if a test point does not have a ground resistor value, it is not connected to the ground or the negative pole, and for a circuit board that does not drop off, there are indeed but few such signals.             Second, for specific test points, the earth resistor value cannot be too small or even small to the ground or to the negative short circuit, nor can it be too large or even too large to open the road. It will have a normal value, which is determined by the circuit in which the test point is located. If the earth resistor value of a test point is obviously deviated from the normal value, the fault element can be clearly determined in the circuit in which the test point is located, which is the theoretical basis for judging the possible existence of the fault element by using the ground resistor value.            

The above two points are the basic value of the ground resistor value in maintenance.             The bags in voltage caused by the resistor between the pension and the contact resistor between the pension and the measuring points can sometimes not be ignored when the earth resistor value is actually measured. For errors caused by resistor between pen, in the case of a digital multimeter; the relative measurement function provided by the multimeter; itself can be used to zero. For the contact resistor between the meter pen and the measuring points, the tip of the meter pen should be used to contact the measuring points reliably as far as possible.

This article is from Allicdata Electronics Limited.