1, the accuracy of the instrument China's electrical instrument is divided into 0.1,0.2,0.5,1.0,1.5,2.5,5.0 seven levels, the meaning of this level refers to the instrument full scale error percentage. For example, the rating is 0.5, and the input current is 5A. The meaning of 0.5 is that when the current meter enters 5A, its maximum error will not exceed 0.5%.
There is another way to describe the error, which is called uncertainty, which has not been fully adopted in the instrument industry in China. Therefore, it will not be described.
2. Advantages of Digital and Analogue Meters: Accurate readings and high accuracy The strengths of the analog meter: You can see the change trend and range of the pointer according to the swing of the pointer, so there are also digital display instruments with light columns. To achieve this function of the analog meter, it is generally used to measure and display the liquid level. It looks more intuitive.
3, the instrument's power supply is generally divided into transformer power supply, switching power supply, battery-powered three.
Switching power supply: Advantage is the wide input voltage range of 70-250V, the disadvantage is poor anti-interference ability, especially in places with large harmonics, such as steel mills, instrument power supply parts are easily damaged.
Transformer Advantages: Anti-harmonic anti-jamming, Disadvantages: Single input voltage level, when ordering need to explain the voltage level, DC power supply is not available.
4, the input measurement signal input measurement signal is divided into half, AC signal and DC signal, DC signal accuracy is generally much higher than the AC signal.
5. The true rms and average multimeter display averages.
The value displayed by the installed meter is generally a true rms value, with strong anti-interference ability, anti-harmonic and frequency change characteristics.
6, the general size is 120 96 80 square
7. Additional function meters In addition to the usual measurement functions, there are additional modules.
1. The communication module supports RS-485 modubus RTU protocol 2. Transmitting module 4-20mA Transmits the measured signal 3. The control module outputs the relay to realize the over-range alarm for the set voltage and current values.
8. Set the current full-scale ratio, according to the actual installation transformer ratio can be set by the user from 5A-8000A according to the national standard series value.
9, the speed of response Ordinary digital displays generally use a dedicated chip, dedicated chip because of a lot of functions, so the response time is relatively slow, generally only 3-5 valid values ​​for one second.
In some special occasions, where the customer requests a fast response, this parameter response speed will be involved.
10, above said so many are for industrial frequency 50Hz instrument
There are also some special instruments on the market, such as mid-frequency 400Hz watches, mainly for aviation; also high-frequency watches, such as 20kHz, mainly used in some high-frequency equipment, such as super audio power, inverter output current.
11, data acquisition software on the 485 interface with the instrument, usually many users need to write their own collection software in the instrument electronics professional production of digital display controller, so that the customer's production efficiency has been the greatest improvement, as much as possible for customer service.
The face of the market with a large number of digital electrical instrument, the model is complex, when the order is not the mistake, is to get the hand is not what you want.
Today I just took the opportunity to discuss with you how to buy a digital electric meter. I hope to help everyone. Electrical instrumentation is a general term, and multimeters and mounted instruments are all electrical instruments. Our main focus here is on the purchase of digital display meters.