In this manual, users will learn how to use the DMM, an indispensable tool that can be used for circuit diagnostics, electronic design studies, and battery testing. Hence the name multi - meter (multiple measurement).
The main parameters to be checked on this device are voltage and current. A multimeter is also great for some basic he alth checks and troubleshooting. It is often used in the repair of equipment. The symbols on the multimeter allow you to understand how much the voltage or current in a certain section of the circuit differs from the original value.
What equipment is made of
Before you start using the technique, you need to find out what parts it consists of. The designations on the multimeter can be obtained by measuring a specific area. Without knowledge of the necessary terminals and contacts, the work cannot be done.
The multimeter consists of three parts:
- Display.
- Selection knob.
- Ports.
The display usually has four digits, plus the option to display a negative sign. Some device models have backlit displays for better viewing in low light conditions.
The selection knob allows the user to set the mode and read various readings such as milliamps (mA) of current, voltage (V) and resistance (ohms).
Two sensors are connected to two ports on the front of the device. COM stands for common connection and is almost always connected to the ground or "-" circuit. The COM probe is usually black, but there is no difference between a red and black connection other than the color. The designation on the multimeter through each of these conductors will be the same.
10A is a special port used to measure high currents (more than 200mA). mAVΩ is the port where the red probe is usually connected. It allows you to measure current (up to 200 mA), voltage (V) and resistance (Ω). The end of the probe has a connector that connects to a multimeter.
Voltage measurement
Now, having de alt with the device of the multimeter, you can proceed to the simplest measurements. First you should try to measure the voltage on the AA battery. The designation on the multimeter will show the level of passing current in a particular area.
To do this, the following actions are performed:
- Connect black probe to COM and red probe to mAVΩ.
- Set the multimeter to "2V" in the DC range. Almost all portableelectronics use direct current, not alternating current.
- Connect the black probe to battery ground or "-" and the red probe to power or "+".
- Squeeze the probes by lightly pressing on the positive and negative terminals of the AA battery.
If a new battery is applied, users should see about 1.5V on the display. AC voltage (such as wiring from walls) can be dangerous, so it is rarely necessary to use the AC voltage setting (V with a wavy line next to it). It is important to observe each parameter of the original value here. To answer the question of how to use a multimeter, detailed instructions for beginners to measure the voltage on different pins will be presented below.
Measuring the voltage taken from the power supply
To do this, you need to set the knob to "20V" in the DC range (it is indicated as V with a straight line next to it).
Multimeters don't usually have autoranging. Therefore, users should set the multimeter to the range it can measure. For example, 2V measures voltages up to 2 volts, while 20V measures voltages up to 20 volts. In case a 12V battery is measured, the 20V setting is applied. If the parameter is set incorrectly, the meter screen will not change at first, and then a value of 1 will appear. beginners may contain differentmeasurement rules. It all depends on the type of digital or analog device. There are advanced models that have additional features related to current tracking on microcontrollers.
Other measurements
With this device, you can check various parts of the circuit. This practice is called nodal analysis and is the main method in circuit analysis. When measuring the voltage in the circuit, you need to track what indicator is needed for each section. First, the entire circuit is checked. By measuring from where the voltage is applied to the resistor and then to ground, on the LED, the user should see the total voltage of the circuit, which should be about 5 V. The AC designation on the multimeter in this case will not work. To do this, you will need to switch to another mode, described above.
Sampling overload
The resistance designation on the multimeter may not be displayed. This may be due to malfunctions. What can happen is to choose a voltage setting too low that you need to measure the question is interesting. Nothing bad will happen. The meter will simply display the number 1. This is how the meter indicates that it is overloaded or out of range. To change the reading, change the multimeter pen to the next maximum setting.
Selection knob
Why does the indicator knob show 20 V and not 10, a question that users often ask. If you want to measure less than 20V, you need to switch to the 20V setting. This will allow you to read the reading from 2.00 to 19.99. First digitmany multimeters can only display "1" so the ranges are limited to 1 9.99 instead of 9 9.99. Therefore, the maximum range is 20 V instead of the maximum range is 99 V. The capacitance designation on the multimeter in this case will be inaccurate. However, such errors are insignificant.
Must stick to DC circuits (settings on multimeter with straight lines, not curved lines). Most devices can measure AC systems, but they can be dangerous. If you need to check if the outlet is turned on, you should use an AC tester.
Resistance measurement
The designation of microamps on a multimeter makes it possible to check the resistance in different electrical sections. This is especially useful when testing microcircuits.
Normal resistors have color codes located on them. It is impossible to know all possible combinations and their definitions. There are many online calculators that are easy to use. However, if the user ever finds himself without access to the Internet, a multimeter will help to measure the desired parameter.
To do this, choose a random resistor and set the multimeter to 20 kOhm. Then press the probes against the legs of the resistor with the same pressure as when pressing a key on the keyboard. The meter will read one of three values - 0, 00, 1, or the actual value of the resistor. In this case, the designations on the multimeter panel can be switched in several modes.
In this casethe meter reading is 0.97, which means that the value of this resistor is 970 ohms, or about 1k ohms. Note that the meter is in 20 kΩ or 20,000 Ω mode, so you need to move three decimal places to the right, which will equal 970 Ω.
Highlights when measuring
Many resistors have 5% tolerance. This means that color codes may indicate 10 thousand ohms (10 kΩ), but due to variations in the manufacturing process, a 10 kΩ resistor may be as low as 9.5 kΩ or 10.5 kΩ. In the instructions, the description of the multimeter indicates that measurements can only be taken within strictly established ranges.
However, when measured below the established norm, nothing will change. Since the resistor (1 kΩ) is less than 2 kΩ, it is still shown on the display. However, you will notice that there is one more digit after the decimal point, which gives a refinement in the calculation of the final value.
As a rule, a resistor less than 1 ohm is rare. It should be understood that resistance measurement is not perfect. Temperature can greatly affect the reading of the indicator. Also, measuring the resistance of a device when it is physically installed in a circuit can be very difficult. Surrounding components on the board can greatly affect the readings. As a result, ohms may not be displayed correctly on the multimeter.
Current measurement
Reading current is one of the most difficult measurements in the world of embedded electronics. This is difficult because it is necessary to control the current in several areas at once. Measurement works the same asvoltage and resistance - the user must get the correct range. To do this, set the multimeter to 200 mA and work from this value. Current consumption for many circuits is typically less than 200 mA. Make sure the red probe is connected to the 200mA fused port. On a multimeter, the 200mA hole is the same hole/port used for measuring voltage and resistance (output labeled mAVΩ).
This means you can keep the red probe in the same port to measure current, voltage or resistance. However, if the circuit will be using a voltage close to 200mA or more, it is best to switch the sensor to the 10A side to be on the safe side. Overcurrent may cause the fuse to blow, not just show an overload.
Things to remember when measuring
The multimeter acts like a piece of wire - when the circuit is closed, the circuit turns on. This is important because over time, an LED, microcontroller, sensor, or any other measurable device can change its power consumption. For example, turning on an LED could cause an increase of 20 mA for one second and then a decrease for a second as it turns to off.
The instantaneous current value should appear on the multimeter display. All multimeters take readings over time and then average, so readings should be expected to fluctuate. Generally,cheaper meters will average more sharply and respond more slowly.
Continuity check
A continuity test is a resistance test between two points. If the resistance is very low (less than a few ohms), the two points are connected electrically and an audible signal is emitted. If the resistance exceeds a few ohms, then the circuit is open and no sound is produced. This test helps ensure that the connections between two points are correct. The check also helps determine if two points are connected, which shouldn't be. In this case, the volts on the multimeter will be displayed in a strictly set value, without errors.
Continuity is perhaps the most important feature for electronics repairers and testers. This feature allows you to check the conductivity of materials and see if electrical connections have been made.
To measure this parameter, you need to do the following:
- Setting the multimeter to "Continuity" mode. The switch may be different among digital multimeters. You should look for a diode symbol with propagating waves around it (for example, sound coming from a speaker).
- Next, you need to touch the probes together. The multimeter should beep (Note: not all multimeters have a continuity setting, but most should). This shows that a very small amount of current can flow without resistance (or at least very little resistance) betweensensors.
- It is important to shut down the system before checking for continuity.
Continuity is a great way to check if two SMD pins are touching. If you can't tell the difference visually, a multimeter is usually a great resource for testing. When the system is down, continuity is another thing to help troubleshoot power outages.
Here are the steps to take:
- If the system is on, carefully check VCC and GND with the voltage setting to make sure the voltage is correct.
- If a 5V system is running at 4.2V, carefully check the regulator, it may be very hot, indicating the system is drawing too much current.
- Turn off system and check for continuity between VCC and GND. If you hear a beep, then there is a short circuit somewhere.
- Turn off the system. Continuously verify that VCC and GND are properly connected to the pins of the microcontroller and other devices. The system may turn on, but individual ICs may not be connected correctly.
Capacitors will change rates until they are filled with energy, and then they will act as an open connection. Therefore, a short beep will appear, and then there will be no beep when the measurement is taken again.
Replacing the fuse
One of the most common mistakes a new multimeter makes is measuring current on a breadboard by probing from VCC to GND. This will immediately short to ground through the multimeter, causingto loss of power supply. As current flows through the multimeter, the internal fuse gets hot and then blows when 200 mA flows through it. It will happen in a split second and without any real audible or physical indication that anything is wrong.
If the user tries to measure the current with a blown fuse, he will probably notice that the meter reads "0, 00" and that the system does not turn on, as when a multimeter is connected. This is because the internal fuse is broken and acts like a broken wire or open connection.
To replace the fuse, you need to unscrew the bolts with a mini screwdriver. The DMM is fairly easy to take apart.
After removing the bolts, the following steps are performed:
- The battery plate is being removed.
- Two screws are removed behind the battery plate.
- The front panel of the multimeter is slightly raised.
- Now you should pay attention to the hooks on the bottom edge of the front of the panel. You will need to move the case slightly to the side to disengage these hooks.
- Once the face piece is unhooked, it should come off easily.
- Next, the fuse is carefully lifted up, after which it should pop out of its socket on its own.
Be sure to replace the correct fuse with the correct type. If you select a device of a different type of voltage, the multimeter will stop functioning. The components and circuit board traces within the device are designed to accept variouscurrent values. Therefore, when disassembling the case and assembling it, it is important not to damage the coatings and contacts.
Conclusion
When using a multimeter, it is important to correctly set the desired mode. A common mistake many users make is that they incorrectly set the required values and measure high voltage sources. This can lead not only to a complete failure of the equipment, but also to injuries to the person measuring it. It is best to use a multimeter to measure the value on microcontrollers and digital boards.
