Look for 2 types of instruments:
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Look for these 2 types of instruments: 1) Some kind of PID controller that accepts 4-20mA signals on inputs A and B; it controls the duration for which the two contacts are open or closed based on the magnitude and sign of the difference between A and B, with no action taken when the difference is zero. (The time it takes to actually control the forward and reverse rotation of the motor) It is not necessary to be able to control the on/off timing as well. 2. For a certain type of electric actuator, when a 4-20mA signal is applied, it can be set so that no output occurs at 12mA; the contact on route A activates at 12-4mA, while the contact on route B activates at 12-20mA. If you know anyone who can help, please provide the specific manufacturer model; if possible, also include the price. Thank you! :)
How simple it is to get a small PLC. It’s estimated to be about the same price as the two instruments. It can be done with around 2,000 RMB. Just the cost of the PLC.
Reply 2# pH7 requires 2 analog modules, so it will be more expensive, right?
If using an S7-200, I recall that the CPU214 costs around 1,200, and the 2-channel AI module costs around 700. So in total, around 2,000. The S7-200 comes with several DI and DO inputs/outputs
This post was last edited by liuei on 2010-7-24 at 10:07. The instrument with the first function is called a servo controller. For electric valves, one of its inputs is a given 4-20ma signal, while the other input is a 4-20ma signal representing the valve position feedback. When these two inputs differ from each other, the forward and reverse contacts close, thereby controlling the operation of the motor! The second function: it can be achieved using a regular digital display with alarm contact outputs
The first method involves using the Yokogawa UT750 temperature controller; however, as per your request, it is necessary to use the communication software’s editing functions to download the settings back into the controller. If there is no requirement regarding the duration of the on/off period, this step might not be necessary. The second type refers to a range-control module based on a V-shaped curve at 12 mA; such modules may be available in Honeywell’s integrated electric valves, and there is also an intelligent module of this kind in an integrated valve manufactured in Germany. I’ll check with the company regarding the brand name