Digital Multimeter purchase Guide

Digital Multimeter purchase Guide

Multimeter is the most basic tool in the field of electronic testing, and is also a widely used instrument. because of its low price, simple operation, complete functions, and extensive use, professional electronic engineers often ignore the following problems:

1. Because the precision and resolution of the multimeter are insufficient, estimation may often lead to "human error:

2. Because of the different multimeter testing methods, the multimeter often leads to "error" in the testing of different signals and non-sine wave standard signals ":

3. Operational Safety, feasibility, and protection: due to the poor protection of the multimeter itself, testers are not required to be careless during the test. Otherwise, the multimeter may be damaged as necessary ......, Therefore, based on my years of experience, we recommend that you select your multimeter as needed!

So how to choose a multimeter?
1. Select the number of digits and precision of the multimeter as needed.
The display digits and precision are the two most basic and important indicators of the multimeter. The two are closely related. Generally, the higher the precision of the multimeter, the opposite. However, because the measurement principle is different from the quality standards of various manufacturers, in the same digit, some multimeter has a high precision, but some are poor. For example, the 41/2 multimeter is used, and some models have a precision of 0.025% while others have only 0.8%. There are two ways to display the number of digits: Count display and number of digits display. The Count display is the actual expression of the range of digits displayed by A multimeter. It is generally expressed by the number of digits because people are used to the convenience of the traditional method. For example, the 3000-bit counter display indicates that the maximum display value of the multimeter can reach 3999, And the 1000-bit counter display can only reach 1999. When the 220vac voltage is measured, it can be seen that the 3000-bit display is more than one decimal place after the 1000-bit display: this resolution is an order of magnitude higher, which is in the debugging and testing of highly sensitive micro-electrical signals, A high-sensitivity multimeter will play a greater role. At the same time, the Count display and the number of digits display can be converted: calculate the number of digits in the Count display, and then take the previous number as the denominator of the score, and then subtract this number from 1 to become a molecule, the number of digits is displayed. For example, the number of 3000 bits is counted, and the number of BITs is 3 2/3 bits.

2. Select A multimeter measurement method and AC frequency response as needed
Generally speaking, the multimeter's measurement method is mainly for the measurement of the AC signal. We all know that there are many types of AC signals and various complicated situations. As the AC signal frequency changes, various frequency responses may occur, measure that affects the multimeter. The multimeter can measure the AC signal in two ways: Average Value and true value. The mean value measurement is generally for a Pure sine wave. It uses the Estimation Mean Method to Measure the AC signal, while the non-sine wave signal will produce a large error, if the sine wave signal suffers harmonic wave interference, the measurement error will also change greatly. The real valid value measurement uses the instantaneous peak value of the waveform multiplied by 0.707 to calculate the current and voltage, ensures accurate reading in distortion and noise systems. In this way, if you need to detect ordinary digital data signals, the average multimeter will not achieve the real measurement effect. At the same time, the frequency response of the AC signal is also essential, and some can be up to 100 kHz.

3. Select the functions and measurement range of the multimeter as needed
Different multimeter manufacturers will design different function measurement ranges. Generally, common multimeter can test AC/DC voltage, current, resistance, and disconnection. However, some multimeter does not set the current function to reduce costs. On this basis, some multimeter has added some other functions for ease of use. For example, diode, multimeter battery test, transistor Hef, capacitor, frequency, temperature, etc. Due to the development of electronic technology, some famous manufacturers such as "Tektronix, Fluke, and HP" have added more advanced functions based on traditional parameters and components, such: duty cycle test, DBM value test, maximum and minimum value record holding function, etc. In short, the functions of the multimeter will follow the test needs, and experienced manufacturers will create more and more superior functions. However, on the basis of our pursuit of the multimeter function, we cannot ignore its measurement range. We also test the current. Some multimeter can reach 20a, but some are only 40mA or smaller.

4. Select Your multimeter as needed
Like most instruments, the multimeter also has measurement stability. The accuracy of the measurement results is related to the time used, the environmental temperature and humidity, and so on. If the stability of the multimeter is poor, the multimeter will be "self-contradictory" when used for a period of time-the measurement results are inconsistent. Therefore, some manufacturers pay close attention to this problem: for example, Fluke promised lifetime traceable calibration and warranty in the latest new product sales.
Most maintenance engineers use A multimeter, which is most worried about the poor protection of the multimeter. Accidental insertion of an incorrect table or test file may cause unnecessary damage to the multimeter and affect their work. Therefore, the safety of A multimeter is very important. Some good multimeter provides good self-protection. For example, when a multimeter inserts an incorrect Table Line, an alarm will automatically generate a beep ...... In this way, the purchase of a multimeter should not be blindly greedy for cheap, practical and easy to use.

5. Use a multi-function multimeter as needed
As described in section 3, many multimeter functions are added due to the development of electronic technology.
1. Temperature Measurement
In the electronic maintenance, the multimeter with this function allows you to check the degree of heat of electronic components, such as welding when selecting components, measuring temperature to prevent damage to components.
2. measure both AC and DC Components
In electronic testing, the signal we encounter is not a pure AC or DC signal. We need to observe the total valid values of the waveform (including AC and DC ), in order to analyze the power consumption of the circuit and find out the cause of some parts burning-DC imbalance.
3. DBM and millivolt Value Measurement
The so-called dBm value measurement, that is, the Low Level Measurement-DB value measurement. DB is generally expressed in this formula: DB = 20logv test/V parameter. If you change the V reference voltage, we can measure the corresponding value through testing and comparison: for example, to analyze the voltage gain of the voltage generator.
4. Peak maintain
Using the multimeter's true value measurement, we can measure the instantaneous peak voltage of irregular AC signals with a width greater than 0.25 milliseconds, and automatically maintain the voltage, which is conducive to finding the cause of component and device failure.
5. △relative Value Determination
With this function, we can determine the relative value, that is, we test the difference between the voltage or current and the reference voltage or current. The relative mode of the capacitor can clear the stray capacitance in the reading.

Post-Note: The digital multimeter is the same as the ordinary product. It is costly to add any function, and the manufacturer will increase the sales price accordingly, for some impractical and rarely used features that can be implemented through other basic functions, we do not recommend that you purchase them. We are pursuing practical and useful features, but it is cost-effective!