How to check the serviceability of resistor with a multimeter
Resistor - is an element without which it can not do any one scheme. It is therefore not just desirable, but necessary to know how to correctly checked the serviceability of resistance (resistor) using a measuring instrument (multimeter).
Content
checking algorithm
types of labels
Marking SMD elements
inspection
Check for an open
Check the denomination
What is tolerance, and why is it important
Checking variable resistor
conclusion
checking algorithm
Despite the fact that there are numerous modifications of the resistors, the algorithm checks the majority of them are reduced to the following three stages, namely:
1. Visual inspection.
2. Testing details for an open or breakdown (an extremely rare phenomenon in resistors).
3. To verify compliance with the nominal value of the resistance parameter.
The first three points is not likely to cause trouble, but on the third to stop in more detail than we are with you are going to do.
After all, in order to verify compliance with par value, need to know this is the face value. And if you have a diagram of the device, it's simple here.
We read the chart find the desired item, and in the accompanying documentation will know its parameter. But that's the trouble, most modern devices are not equipped with circuits. The way out of this position is to determine the resistor value on the label.
types of labels
In Soviet times, all the necessary information about the resistors marked on the product, and if the item is damaged, its parameters are just pointing in the accompanying technical documentation.
Currently accepted color coding of products, which allows, even when extensively damaged element (in the absence schemes) determining the nominal and tolerance resistance.
Deciphering this marking is as follows:
Marking SMD elements
But resistors mounted version, mounted with the help of robotic systems are digitally coded in the form of three digits. The first two represent the resistance value, but the third indicates the factor:
So, we figured out how to determine the denomination of interest to us resistor, now let's go back to our algorithm and start checking elements of interest.
inspection
In the majority of cases a work stoppage resistor is overheating, which is very easy to identify on the blackened body parts
As you can see from the photo detail number 1 just below replacement, but the neighbors need to be checked.
Check for an open
an open test is performed as follows: take the device (meter), the controller and probes possess as shown in photo enlarge
Then touch the ends of test leads to the terminals of the resistor and if the display see "1" it means that the item is in breakage and should be replaced.
Note. Though check and can be carried out directly on the board (without watering) must always be borne in mind that in complex schemes detail can make calls via the circuitous chain. On failure or serviceability of the element with 100% certainty can only talk when one of vypayat legs. Just checking the polarity does not matter.
Check the denomination
If you vypayat resistor or wish to check newly acquired, then follow these steps:
Take the device, connect the probes to the corresponding connectors on the controller expose measurement limit as close as possible to the intended nominal resistor. And produces a measured parameter.
Note. During testing, do not touch the fingers of the conclusions and exposed parts of the probe. This is necessary for accuracy of measurement, since the human body is also resisted.
We read the testimony from the device and perform a comparison with a nominal value. And I want to tell you that in 99 cases out of 100 they will be different. Since all resistors have a tolerance.
What is tolerance, and why is it important
This parameter is set by the manufacturer, and indicates how the product parameter may differ from the nominal value. If you set the item with the corresponding parameter is not required, it can lead to rapid overheating and failure of the resistor. And accordingly inoperable newly renovated unit.
So, how to check the standard resistor seems understandable, but how to check the trimmer (variable) resistor talk further.
Checking variable resistor
Check this resistance is actually a little different from the usual test resistor, except for a few moments, namely:
We trimmer three output legs and if you make a measurement between "1" and "3" on the instrument will close nominal value of the resistor.
If the measuring device connected to the terminals "1" - "2" or "2" - "3" (no difference in principle), the resistance value (at Regulation of the trim arms) should vary smoothly from zero to a nominal value obtained when measured by "1" conclusions - «3».
If during adjustment readings are periodically changed to 1 (infinite resistance), the trimmer fail and need to replace it.
conclusion
Here thus comes resistor checked using a measuring instrument (multimeter). If the article was useful to you, you will appreciate it Like. Thank you for your attention!