How to choose between digital voltmeter and ammeter?

1. Instrument size

In other words, instrument size is a very fundamental issue. The digital display instrument should be installed on the cabinet, so comprehensive consideration is required. If it's too big, it may not fit. If it is too small, the display number cannot be seen clearly. In addition, large instruments generally have powerful function expansion and the same function price. It can be expensive and has poor functional scalability for small instruments. 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.

2. Display numbers

This is directly related to measurement accuracy. Generally speaking, the higher the display digits, the more accurate the measurement, and the more expensive it is. There are mainly the following types: II (99, special); (III) (999, rarely); three and a half years (in 1999, ordinary digital displays dominated); IV (9999, mainly intelligent digital displays) ; 4:30 (19999); three-quarters and three-quarters (3999); 5. V (commonly used in counters, totalizers and high-end instruments). Users can choose from a variety of digital display instruments based on measurement accuracy requirements.

3.Input signal

The measurement signal is directly input to the instrument. Some industrial signals are directly connected to instruments for measurement. After conversion, some signals will be converted into instruments. The nature of the measurement signal must be clarified. Otherwise, the purchased instrument will be unusable or even damaged. Original equipment. To find out the type of signal: current or voltage, AC or DC, pulse signal or linear signal, we also need to know the magnitude of the signal. The name of the instrument 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 a shunt to obtain a voltage signal); the input signal is a 0-10vdc tachometer (called a tachometer, the input signal is Voltmeter, because the frequency converter converts the speed signal into a voltage signal).

4.Work ability

All digital display instruments need working power. The working power supply of digital display instruments mainly includes: 220VAC; 110/220V AC; 85-265vac/DC switching power supply, 24VDC (generally customized), 5VDC (small instrument panel).

5.Instrument functions

Instrument functionality is often modular. Alternatively, the price of the instrument will vary based on functionality. The digital display has the following optional functions: alarm function and number of alarm output groups (ie, relay action output), feed output and output voltage size and power, transmission output and transmission output type (4-20mA or 0-10V, etc.), communication Output and communication methods and protocols (RS485 or RS232, MODBUS or other protocols) for regulating control instruments. More functions can be selected. For details, 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 that need attention

Measurement accuracy (the smaller the value, the more accurate it is), response speed (the smaller the value, the faster the response), working environment, temperature coefficient (the smaller the value, the less affected by temperature), and strong overload capability.

7.Special requirements

If the user has special requirements, it is recommended that the manufacturer confirm whether the requirements are met. Don't take this for granted. For example, IP protection level, high-temperature workplaces, strong interference situations, special signal situations, special working modes, etc.

In fact, the choice of digital instruments is not complicated. For simple numerical display you can use this. For first-time users or users who use complex digital displays, if they master the above points, they can choose a good one. Buy the right product.