Selection analysis of display instruments

1. Accuracy of the instrument

China's electrical instruments are divided into seven levels: 0.1, 0.2, 0.5, 1.0, 1.5, 2.5, and 5.0

. This level means the percentage error of the full scale of the instrument.

There is another way to describe the error, called uncertainty, which has not been fully adopted in the instrument industry in China, so I will not elaborate on it.

2. Digital display and analog meter

The advantages of digital meters are accurate readings and high precision

The advantages of analog meters are that the trend and range of changes in the measurement can be seen according to the swing of the pointer

So there are also digital display instruments with light columns, which are designed to achieve this function of analog meters.

3. Power supply of the instrument

Generally divided into three types: transformer power supply, switching power supply, and battery power supply.

The advantage of switching power supply is that the input voltage range is wide, 70-250V,

and the disadvantage is that the anti-interference ability is poor, especially in places with large harmonics, such as steel mills, where the power supply part of the instrument is easily damaged.

Advantages of transformers: anti-harmonic and anti-interference
Disadvantages: The input voltage level is single, and the voltage level must be specified when ordering. DC power supply is not available.

4. Input measurement signal The

input measurement signal is divided into two parts: AC signal and DC signal

The accuracy of DC signal is generally much higher than that of AC signal.

5. True effective value and average value

The multimeter displays the average

value The value displayed by the installed instrument is generally the true effective value, which has strong anti-interference ability, anti-harmonic and frequency change characteristics.

6. External dimensions

Generally, there are 120, 96, 80, 72, 46 squares

7. Additional functions
In addition to the ordinary measurement functions, the instrument also has additional modules.

1. The communication module supports RS-485 modubusRTU protocol

2. The transmission module 4-20mA? Transmits the measured signal

3. The control module outputs through the relay to realize the over-range alarm for the set voltage and current values.

8. Ratio setting

The full range of current, according to the actual transformer ratio at the time of installation

It can be set by the user from 5A-8000A according to the national standard series value.

The digital display can set the ratio of any channel separately, which is also a practical function.

9. Response speed

Ordinary digital display meters generally use dedicated chips. Because dedicated chips have many functions, their response time is relatively slow

. Generally, they can only output 3-5 effective values ​​per second.

Our digital display meter, the digital display meter of Best Industrial (Hong Kong) Co., Ltd., uses its own computing platform, and can output one effective value per cycle at the fastest, that is, one effective value every 20ms, and output 50 data per second.

In some special occasions, where customers require fast response, this parameter response speed will be involved