Mass flow meter

There is no difference; the factory just needs to provide different power cables. More and more 2-wire instruments are available these days, which also facilitates wiring in factories by eliminating the need to run additional power cables.

Most of Emerson’s mass flow meter transmitters have power supplies that are adaptive to 24V and 220V. There are 2-wire mass flow meters, but I have hardly ever seen them in use.

For a transmitter, its output voltage is less than or equal to the lowest supply voltage minus the voltage drop across the load resistance and the transmission wire resistance; moreover, the current must be less than or equal to the transmitter’s output current. The power is less than or equal to the product of the voltage and current mentioned above. It is usually less than 90mW. If the above three conditions are met, a two-wire system can be used. It provides the operating voltage for the transmitter while also serving as a signal transmission medium. For two-wire instruments, what is usually seen is just a regular transmitter. However, for unconventional tables, it offers many functions, the conversion circuitry is complex, and as a result, its power consumption is relatively high. It is difficult to meet the above three conditions. Therefore, the only way to create a 4-----20mA transmitter is by using an external power source. In the four-wire system, there is 200AC and 24DC. But DC has better interference resistance than AC, and when powered by 220V, a circuit that converts 220AC to 24DC needs to be added inside the meter. Invisibly, the size and weight of the instrument panel have increased. These are the watches available on the market today; there are fewer and fewer watches that operate on 220V power. Most have aligned with 24DC. For two-wire meters, the output is an active signal; whereas four-wire meters allow you to choose between an active and a passive signal. Choose to look. Please point out any mistakes. I will accept it with an open mind.

Putting the flow meter aside, let’s talk about electric valves. What are your thoughts on 220V and 24V for electric actuators?

I’m not quite sure about this; I humbly ask for your guidance. . . .

The previous Haiyou’s answer to this question was a bit subjective. Firstly, both four-wire mass flow meters and two-wire ones are available from Emerson; the two-wire version was introduced quite recently and has not been widely used. Secondly, regarding the issue of 220 and 24, one member used a very apt term: \"adaptive.\" That’s exactly it; it’s not necessary to convert 220 to 24 first and then use 24 throughout ； In other words, there is no conversion circuit for 220 volts to 24 volts. If there are any differing opinions, feel free to discuss them in detail. Additionally, what the salespeople say is meant to help people understand more quickly and gain an intuitive grasp, and it is not necessarily the exact answer.