Second, the system requirements 1, control temperature accuracy requirements ± 1 °C;
2. When the temperature is lower than a certain value A, the power of the two groups of thermal cycling systems is fully on. When the temperature is higher than this value A, the output is adjusted according to the temperature. The value A can be set;
3, with the upper deviation alarm output;
4, the heating system uses PID control;
5, when the temperature 50 ~ 200 °C, transmission output 4 ~ 9mA
Third, the system structure According to system requirements, we have chosen AI-808AX4XL2L2 as the main temperature controller, the system block diagram shown below: 
The main output of the AI-808 table is used as the control signal of the AIJK6 to control the heating output; the auxiliary output is the transmission output and used as the control signal of the frequency converter 1; the analog output of the frequency converter 1 is used as the control signal of the frequency converter 2. Inverter 2 follows converter 1 and operates.
Fourth, instrument selection and function AI-808 regulator on the basis of the AI-708 regulator also has a manual / automatic bumpless switching operation, with manual auto-tuning and display output value, and as a direct servo amplifier Control the proportional output of the valve position. In this system, the AI-808 meter was used for temperature detection of the air conditioning unit and positive and negative control of the servo motor. The specific model is AI-808AX4XL2L2. The specific module function is as follows:
X optically isolated linear current output module;
X4 Opto-isolated linear current output module, and does not occupy the instrument's internal isolated power supply;
L2 relay contact switch (varistor absorption) output module.
AIJK6 is an intelligent three-phase phase-shift triggering and cycle zero-crossing dual-purpose trigger using single-chip microcomputer technology. It has powerful functions and high reliability, and can adapt to various resistance wires, silicon carbon rods and transformers and step-down transformers of silicon molybdenum rods. Various industrial furnaces such as tungsten wire can also be used to control the motor soft start. Its main features include:
◠0～20mA (0～5V)/4～20mA (1～5V) signal compatible input;
â— When the load is resistive, its output power is proportional to the input signal;
â— has a lack of phase detection, over-current detection and alarm function;
â— Automatic synchronization function, no phase sequence is required when connecting thyristor trigger wires;
â— The use of full-spot isolation and "burning is not bad" technology, the reliability is very high, causing little interference to the input;
â— Contains switching power supply, can be directly used 220VAC power supply, and with 5V and 24V DC power supply output.
Five, parameter settings
1, AI-808 instrument parameter settings:
According to specific requirements, the main parameters of the AI-808 instrument are set as follows:
HIAL 120 (value A) Use the upper limit alarm output to control the speed reference switching of the inverter, use the multi-function input terminal of the inverter to complete;
DHAL 5 system requires positive deviation alarm within 5 degrees;
Ctrl 1 uses AI artificial intelligence adjustment;
Sn 0 is input as K thermocouple;
DIL 50 inputs the lower limit display value, here does the transmission output lower limit corresponding temperature value;
DIH 650 enters the upper limit display value, here the temperature value corresponding to the upper limit of the transmission output;
OP1 4 4~20mA linear current output;
ALP 1 upper limit alarm output by AL2, positive deviation alarm output by AL1;
Run 2 automatically adjusts state and disables manual operation;
2, ALJK6 settings
The setting of AIJK6 is set by a 6-bit DIP switch:
The first bit is used to select the input signal specification. OFF indicates the input is 0 to 20mA or 0 to 5V. ON indicates the input signal is 4 to 20mA or 1 to 5V. The voltage or current input is selected by a jumper in the system. The input signal is 4 ~ 20mA, so the first bit is set to the ON state;
The second wiring mode selection has been set correctly before leaving the factory, no need to change, AIJK6 should be in the ON state;
The third bit is used to select the phase-shift/zero-crossing trigger mode. OFF indicates the phase-shift trigger. The system uses a phase-shift trigger.
The fourth bit is used for phase-missing alarms, where OFF is set to indicate that any phase in the three phases will alarm if only one of the phases is missing or the thyristor is punctured;
The fifth bit is used to select the IN2 function for current feedback or to adjust the soft-start/soft-stop delay time. The system is used to adjust the soft-start/soft-stop delay time and is set to OFF.
Bit 6 for special functions, set to OFF
There are two jumpers on the AIJK6 board. Select whether the main inputs IN1 and IN2 are current input or current input respectively. This is set as current input.
6. Conclusion After the instrument parameters are set, PID self-tuning is performed. After the self-tuning is completed, the observation control effect is good enough to achieve the control effect of imported instruments.