1. Meter size. In other words, the size of the meter is a very basic question. The digital display instrument should be installed on the cabinet, so it is necessary to consider the overall coordination. If it is too large, it may be inappropriate. If it is too small, the display number cannot be clearly seen. In addition, large-scale instruments generally have strong functional expansion and the same functional price. It may be expensive, and small instruments may have poor scalability in terms of functionality. At present, the main international standard sizes of digital display panels are: 48*24mm; 48*48mm; 48*96mm; 72*72mm; 96*96mm; 96*48mm; 160*80mm. Digital display voltmeter
2. Display the number of digits. This is directly related to measurement accuracy. Generally speaking, the higher the display digits, the more accurate the measurement and the more expensive the price. There are mainly the following types: two (99, special); three (999, rarely); three and a half years (in 1999, ordinary digital displays accounted for Dominance); four (9999, smart digital display dominates); half past four (19999); three-quarters and three-quarters (3999); five, five (commonly used in counters, totalizers and high-end instruments) , The user can select multiple digital display instruments according to the measurement accuracy requirements.
3. Input signal. Refers to the measurement signal directly input to the instrument. Some industrial signals are directly connected to the instrument for measurement. After conversion, some signals will be converted to instruments. The nature of the measurement signal must be clarified. Otherwise, the purchased instrument cannot be used or even damaged. Original equipment. To find out the type of signal: current or voltage, AC or DC, pulse signal or linear signal, etc., but also to understand the size of the signal. The name of the meter is different from the concept of the input signal. For example, the input signal is a 0-75mVdc ammeter (the name is an ammeter, but the input signal is a voltage signal, because the current passes through the shunt to obtain the voltage signal); the input signal is a 0-10Vdc tachometer (the name is a tachometer, and the input signal is a voltmeter , Because the inverter converts the speed signal into a voltage signal).
4. Work ability. All digital display instruments need working power. The working power of the digital display voltmeter mainly includes: 220Vac; 110/220V AC; 85-265VAC/DC switching power supply, 24Vdc (generally customized), 5Vdc (small panel meter).
5. Instrument function. The instrument function is usually modular. Or, the price of the meter will vary depending on the function. The digital display has the following optional functions: alarm function and the number of alarm output groups (ie, relay action output). , Feeder output and output voltage size and power, transmission output and transmission output type (4-20mA or 0-10V, etc.), communication output and communication method and protocol (RS485 or RS232, Modbus or other protocols)) for control The adjustment of the instrument has more optional functions. Please refer to the manufacturer's selection range to select the standard model, and communicate with the manufacturer to confirm that it can be ordered.
6. Several important parameters to pay attention to: measurement accuracy (the smaller the value, the more accurate), the response speed (the smaller the value, the faster the response), the working environment, the temperature coefficient (the smaller the value, the smaller the value is affected by temperature), overload strong ability.
7. Special requirements. If the user has special requirements, the manufacturer should be advised to confirm whether it meets the requirements. Don't take this for granted. For example, IP protection level, high-temperature workplaces, strong interference occasions, special signal occasions, special working modes, etc.
In fact, the choice of digital meter is not complicated. For simple digital display, you can use it. For users who use or use complex digital displays for the first time, if they master the above points, they can choose the right product.
Jan 19, 2023
