Analysis of performance and application of secondary instrument for Yudian display control

1 Overview The products of Xiamen Yudian Automation Technology Co., Ltd. are taken from the display and temperature control secondary instruments. The products have been used in the fields of chemical, thermoelectric, petrochemical, pharmaceutical, metallurgy, machinery, food, paper, plastic, packaging, etc. The sales volume reached 600,000 units, and the products are exported to many countries and regions such as North America, Europe, Oceania, India, Middle East, Southeast Asia and Hong Kong, and have been well received by customers. Yudian has become the largest high-end secondary instrument and intelligent distributed in China. The supplier of the control system.
This paper will analyze the performance and application of the secondary instrument for Yudian display control, so that the user can have a deep understanding of the performance of the secondary instrument for the UAV display control, so that the UAV can be selected according to the actual needs of the user. Display secondary instrument for control.
The performance of the secondary instrument for Yudian display control can be divided into the following categories according to the introduction of its main technical parameters:
Input Specification Output Specification Control Mode Power Supply Dimensional Accuracy The above six types of technical parameters will be analyzed separately.
2 Input specifications First use "true universal input" to describe the input characteristics of the secondary instrument for UAV display control.
In the input specification column, the following is listed:
Thermocouple: K, S, R, E, J, T, B, N, WRe3-WRe25, WRe5-WRe26
F2 radiation pyrometer thermal resistance: Cu50, Pt100
Resistance: 0~80Ω, 0~400Ω
Linear voltage: 0 to 20 mV, 0 to 100 mV, 0 to 500 mV, 0 to 1 V, 0 to 5 V, 1 to 5 V
Linear current: 0~10mA, 0~20mA, 4~20mA
More can be provided, such as linear voltage: 0~60mV, 0~75mV, 0.2~1V, -20~+20mV, -100~+100mV, -5~+5V. Customers can also enter the index table and multi-point correction function to adapt to almost all special input requirements.
For the flow totalizer for flow detection applications, pulse signal input is also acceptable.
From the input specifications listed above, it can be seen that the input characteristics of the secondary instrument for UAV display control are indeed omnipotent, which makes the design selection very simple, and the number of spare parts required by the user can be greatly reduced.
3 Output Specifications Output specifications cover the following categories: analog output, digital output, thyristor trigger output, communication interface, alarm output, voltage output.
3.1 Analog Output Linear Current Output: 0-10mA, 0-20mA or 4-20mA can be defined. The current output is optically isolated, with an internal isolated power supply or an isolated power supply.
The analog output of some instruments is equivalent to the transmission output, that is, the detected parameter value is converted into 4-20mA output, for example, the parameter value is transmitted to the DCS, PLC system, so that both the local display and the detection parameter signal can be Isolation and far-reaching to the control system.
3.2 Switching output relay contact switch output (normally open + normally closed): 250VAC / 1A, 250VAC / 2A or 30VDC / 1A;
SCR contactless switch output: 100-240VAC/0.2A (continuous), 2A (20ms instantaneous, repeat period greater than 5s);
SSR drive voltage output: 12VDC / 30mA (used to drive SSR solid state relay).
Since the control function has two-position control, its corresponding output is the switch quantity output, and the secondary instrument for the U-display control can provide the switch output signals of various voltage and current levels required by the user.
3.3 SCR trigger output can trigger 5-500A bidirectional thyristor, 2 unidirectional thyristor anti-parallel connection or thyristor power module, including single zero-crossing trigger output, single thyristor shift trigger output Single-channel inductive load thyristor shift trigger output, three-way thyristor zero-crossing trigger output, direct three-phase three-wire thyristor shift trigger output.
Some salt bath furnaces, power frequency induction furnaces, quenching furnaces, and molten glass temperature control are nickel-chromium, iron-chromium-aluminum, far-infrared heating elements, silicon molybdenum rods, silicon carbon rods, etc., which are usually used. To the thyristor trigger output, depending on the specific object, different output modules can be used.
3.4 Communication interface supports RS232, RS485 communication interface function; the latest touch screen display instrument with Ethernet interface and with cloud / mobile APP view function.
RS485 communication protocol is AIBUS, MODBUS-RTU dual communication protocol. After installing the corresponding module, it can communicate with the host computer. It can be used as the lower computer of AIDCS intelligent distributed control system, split paperless recorder and touch screen control system.
AIDCS intelligent distributed control system is an open industrial process control system that can realize centralized operation and management through network, and has distributed arrangement and high reliability. “Intelligent distributed” means that the lower position machine is subject to various unpredictable factors. Without the command and network of the upper computer, it can also ensure the basic control work of the on-site industrial site, avoiding accidents or dangers, and solving the shortcomings that the current DCS system is not open and the lower computer cannot be separated from the upper computer and the network.
In Figure 1, various types of detection signals and actuator signals from the industrial site pass through the AIBUS protocol of the RS485 communication interface after the UAV company as the lower-level disk-mounted type, rail-type secondary instrument, or rail-type industrial control module. It is transmitted to the upper computer through the RS232/RS485 converter. The upper computer usually adopts the industrial computer or the ordinary computer with the configuration software installed. Users can also choose to connect to the management computer via a local area network or the Internet to provide managers with real-time data and reports on the industrial site.

Figure 1 Schematic diagram of AIDCS system structure

It is usually possible to connect 50 to 60 instruments with industrial-specific shielded twisted pair cables, and the communication distance is 1.2km. The AIBUS communication protocol is simple, efficient and fully functional. The high-precision meter reads 3 common variables and 1 parameter at a speed of 19.2K and the speed is only 20ms. The economical instrument only needs 50ms, which is 2~10 times faster than the commonly used MODBUS protocol. It adopts the AIBUS protocol. The system can achieve almost the same effect as DCS, regardless of whether it is a small system or a large or medium-sized system. The general meter communication efficiency is low. If the number exceeds a certain amount, the data is updated slowly and the display effect is poor. It can only be applied to small systems.
The touch screen display instrument with Ethernet interface and built-in WEB server has the ability to remotely monitor and operate the instrument through the Ethernet interface using a browser.
The touch screen display meter with cloud/mobile APP viewing function does not require public IP, can penetrate internal network monitoring, and monitors and operates in different places through mobile devices such as smart phones and tablet computers.
3.5 Alarm output can have up to 4 alarm outputs: upper limit, upper limit, lower limit and lower limit 4 channels. There is power-on exemption alarm selection function (that is, the first time the power is off after the power is turned off), and the positive and negative deviation alarms can also be provided.
Some parameters in the production process require an upper limit and a lower limit limit alarm, which can be completed by a display with an alarm function. However, there are also a few important parameters that require both the upper and lower limits to exceed the limit alarm, as well as the upper and lower limits, and the so-called four-limit alarm. For example, some alarm conditions involving large equipment parking interlocks sometimes require upper and lower limit violation signals to be used only for sound and light alarms, so-called pre-alarms, which can be determined by the operator according to the site conditions, while the upper and lower limits are limited. The signal enters the interlock system to park the device. Such a requirement used to require multiple alarm displays to complete. This function can now be done with a digital display instrument with a four-limit alarm.
3.6 Voltage output voltage output has 5V, 10V, 12V, 24V and other specifications for external sensor or low power equipment power supply output.
This feature is very important, it provides the equivalent of a distribution function, which can provide power for field sensors, transmitters and other low-power devices. The most common is to provide two-wire power and signal connections for various pressure and differential pressure transmitters.
4 Control mode has two modes: position control (ON/OFF control) and PID control. PID control has standard PID control and AI artificial intelligence APID control. AI artificial intelligence APID control is a new algorithm for PID control using fuzzy rules. When the error is large, the fuzzy algorithm is used to control the phenomenon of PID saturation integration. When the error is small, the improved PID algorithm is used for control. AI artificial intelligence APID control also has self-tuning and self-learning functions, which not only can self-tune PID parameters, but even if the lag time of the controlled object is long, the control process can be over-adjusted and controlled accurately (see Figure 2). The implementation includes complex control functions such as cascade, ratio, and feedforward.

Figure 2 AI artificial intelligence APID control

The program type instrument has multi-stage program control function, which can realize the rising and falling temperature control of any slope, and has programmable/operable commands such as jump (loop), operation, pause and stop, which allows the program to be modified at any time during the control operation of the program; Using the AI ​​artificial intelligence control algorithm with curve fitting function, smooth and smooth curve control effect can be obtained; the SV transmission output function can be used as the program generator; with the measured value start function, preparation function and five power failure/start events Processing mode selection.
AI artificial intelligence control algorithm is divided into basic type, enhanced type, expert type, enhanced program type, expert program type, heating and cooling double output enhanced type, heating and cooling double output enhanced program type, etc., corresponding products are available for users to choose. .
5 The power supply can accept 100-240VAC, 50-60Hz power supply, and can be powered by 24VDC/AC safe power supply. The protection time of at least 10s (in-plant test reaches 30min) can be provided when the meter is suddenly connected to the 380VAC power supply or the abnormal power supply voltage of the neutral line is suddenly increased.
The AC power here actually covers the two most commonly used power levels in the world: 110VAC (including 120VAC), 220VAC (including 230VAC, 240VAC), 110VAC power supply mainly in North America and Japan, and Europe, Asia and other regions mainly 220VAC. The power frequency is 50Hz, 60Hz, which can be selected by the user. As for the 24VDC/AC power supply option, it is mainly to see if there is a ready-made 24VDC/AC power supply and whether it is desired to wear the same power supply wire and signal cable in the same pipe or even in the same multi-core cable.
6 The external dimensions include panel mounted instrument panels and rail mounted products. The panel instrument panel has the common size of the domestic instrument and the general size of the foreign instrument, such as the common size of the domestic instrument 80×160 or 160×80, such as the foreign instrument general size 96×96, 72×72, 48×48, 96×48, 48 ×96 and so on. The rail type is equipped with D5, E5, E8 type DIN rails.
The instrument with touch screen has three dimensions of 5 inches, 7 inches and 9 inches, and the length and width dimensions are 145×105, 203×150 and 231×170 respectively.
Rail-mounted installation is suitable for occasions where data is not needed or rarely needed. For example, as a lower-level instrument for data acquisition, the rail type can save installation space, and the parameter display and setting operations can be used to install the instrument keyboard display on the upper computer or E8 rail. Finished on.
The panel-mounted instrument panel has a variety of housings with different sizes. The user can select according to the needs. Generally, the instrument with larger size can be selected under the condition of sufficient space. When the space requirement is compact, the small-sized instrument or single-unit can be selected. Channel meters meet the requirements. In the field, it is often encountered that the display instrument needs to be added to the existing instrument panel due to the increase of the measurement parameter display. At this time, it is often necessary to re-open the hole on the instrument panel, because the digital display device has a small external size (equivalent to the common external dimensions) For 1/2 or 1/4) and multi-channel products, it is easier to solve such problems.
7 Accuracy measurement accuracy has 0.3 level, 0.25 level, 0.2 level, 0.1 level and 0.05 level, etc. The high-precision level instrument is tested by low temperature drift high stability circuit, and also uses external Cu50 copper resistor for high level. The precision thermocouple cold junction compensation technology can reduce the compensation error by about ±1 °C compared with the internal compensation of the meter. The high-precision meter adopts 24-bit AD, five- or six-digit display, and the temperature display resolution can reach 0.01 °C.
In most cases, the accuracy of 0.2 and 0.3 may meet the requirements. When the monitoring and control accuracy requirements are particularly high, 0.1 and 0.05 provide higher precision products.
8 Conclusion Yudian display control secondary instrument technology is advanced, rich in functions, in order to make good use of these secondary instruments, give full play to their performance advantages, but also need to deepen the understanding of the performance of the secondary instrument for UMC display control. According to the author's understanding of the performance of the secondary instrument for UAV display control, this paper introduces the performance of the instrument, and then analyzes how to use these functions to realize the various requirements of the user's production site in practical applications.


About the Author:
Fang Yuanbai, professor-level senior engineer, chairman of the Kunming Instrument and Meter Society, consultant of the Technical Expert Committee of China Weighing Apparatus Association, mainly engaged in the application research of instrumentation and control systems.



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