What is the concept of a “three-digit narrow band” in digital display regulators?

I’m hearing this statement for the first time as well; I don’t know what it means. I haven’t seen much of the world. If you find out the answer, please don’t forget to let me know...

Hello, I have a question for you. The passive relay you sent is connected in series with 24V, but the pumps on site are powered by 220V, right? Are you saying that the pump is powered by 220V, and the relay module simply sends a command to the pump?

This post was last edited by feng*aosa on 2015-9-18 at 13:04. It is a simple way of describing a on-off PID control scheme. It is widely used in the temperature control of heat treatment furnaces. The bit refers to the number of alarm contacts (control contacts). 　　The usual two-position control is to cut power when above the upper limit and to supply power when below the lower limit (to control the valve opening and closing). This type of controller reduces (or increases) the control current according to the PID principle when it is above the upper limit, and increases (or decreases) the control current according to the PID principle when it is below the lower limit; whereas when the measurement value is within the range between the upper and lower limits, the control signal remains unchanged until the limit is triggered again. This will keep the controlled value within the upper and lower limits ； Broadband and narrowband refer to the degree to which the upper and lower limits can be close to each other; narrowband means that the difference between the upper and lower limits is less than 5% of the range (I’m not sure if this value is accurate). For two-digit control, the range from zero to the lower limit and from the upper limit to the full scale constitutes the control area, while the area between the upper and lower limits is the holding area. If there are more than 2, three or more regions will be formed; for example, 3 characters result in 4 regions, and 4 characters yield 5 regions. 　　Apart from the two regions between the upper and lower limits, other regions can be assigned different functions. Taking 3 levels (lower, upper, upper upper) as an example, when the value exceeds the upper limit, the control current is reduced (or increased) according to the PID principle; once the uppermost level is reached, another set of PID parameters can be used to modify the control signal (that is, by adding another narrowband), or the control signal can be left unchanged (without adding a narrowband). 　　It’s unclear what the poster means by “maintain”; it might refer to maintaining the signal after reaching the upper limit, or it could have another meaning. On the 4th and 6th floors, @1111111 has developed pressure transmitters and level transmitters that come equipped with a regulator function as well as an alarm function via switches; http://bbs.hcbbs.com/thread-1432900-1-1.html. This can be referred to as 7-bit 6-narrowband proportional control.