Learning to implement Data Types for Temperature Control using Unitronics's VisiLogic / UniLogic is an essential skill for PLC programmers working in Process Control. This comprehensive guide walks you through the fundamentals, providing clear explanations and practical examples that you can apply immediately to real-world projects.
Unitronics has established itself as Moderate - US small-integrator market, OEM machines, building automation, making it a strategic choice for Temperature Control applications. With 1% global market share and 6 popular PLC families including the Jazz 2 and Samba 7", Unitronics provides the robust platform needed for intermediate complexity projects like Temperature Control.
The Data Types approach is particularly well-suited for Temperature Control because all programming applications - choosing correct data types is fundamental to efficient plc programming. This combination allows you to leverage memory optimization while managing the typical challenges of Temperature Control, including pid tuning and temperature stability.
Throughout this guide, you'll discover step-by-step implementation strategies, working code examples tested on VisiLogic / UniLogic, and industry best practices specific to Process Control. Whether you're programming your first Temperature Control system or transitioning from another PLC platform, this guide provides the practical knowledge you need to succeed with Unitronics Data Types programming.
Unitronics VisiLogic / UniLogic for Temperature Control
Unitronics takes a distinctive approach to PLC programming: every controller ships with an integrated colour touchscreen HMI, and the development tool handles PLC logic and HMI design in a single workspace. VisiLogic is the legacy tool for the Vision, Samba, and Jazz product families; UniLogic is the current-generation environment for the UniStream line. Both are free to download and include a complete built-in simulator covering PLC logic, HMI screens, alarms, recipes, and data tables — the sim...
Platform Strengths for Temperature Control:
- Combined PLC + HMI in one unit reduces panel cost
- Free VisiLogic and UniLogic IDEs
- Built-in simulator with both PLC and HMI simulation
- Strong US small-integrator community
Unique ${brand.software} Features:
- Combined PLC + HMI in one unit across Jazz, Samba, Vision, and UniStream
- Free VisiLogic (legacy) and UniLogic (current) IDEs
- Built-in simulator covering PLC logic, HMI, alarms, data tables, and recipes
- Integrated data sampling and trend logging without separate SCADA
Key Capabilities:
The VisiLogic / UniLogic environment excels at Temperature Control applications through its combined plc + hmi in one unit reduces panel cost. This is particularly valuable when working with the 4 sensor types typically found in Temperature Control systems, including Thermocouples (K-type, J-type), RTD sensors (PT100, PT1000), Infrared temperature sensors.
Control Equipment for Temperature Control:
- Electric resistance heaters (cartridge, band, strip)
- Steam injection systems
- Thermal fluid (hot oil) systems
- Refrigeration and chiller systems
Unitronics's controller families for Temperature Control include:
- Jazz 2: Suitable for intermediate Temperature Control applications
- Samba 7": Suitable for intermediate Temperature Control applications
- Vision V350: Suitable for intermediate Temperature Control applications
- Vision V570: Suitable for intermediate Temperature Control applications
Hardware Selection Guidance:
CPU selection across Unitronics ranges from the Jazz 2 micro series (tiny applications, basic motor control, simple process monitoring with 10-20 I/O) through Samba 7" (small machine control with touchscreen HMI), Vision V350/V570 (medium machinery with larger HMI), and UniStream 7" / 15.6" (flagship combined PLC+HMI for mid-to-high complexity applications with advanced features like UniCloud, cel...
Industry Recognition:
Moderate - US small-integrator market, OEM machines, building automation. Unitronics' combined PLC+HMI controllers are uncommon in high-volume automotive manufacturing but appear in automotive tier-2 and tier-3 supplier shops, single-machine workcells, and after-market test fixtures. The cost advantage and single-unit PLC+HMI approach makes Unitronics attractive for small...
Investment Considerations:
With $$ pricing, Unitronics positions itself in the mid-range segment. For Temperature Control projects requiring intermediate skill levels and 2-3 weeks development time, the total investment includes hardware, software licensing, training, and ongoing support.
Understanding Data Types for Temperature Control
PLC data types define how values are stored, their valid ranges, and operations that can be performed. Proper type selection ensures accuracy and memory efficiency.
Execution Model:
For Temperature Control applications, Data Types offers significant advantages when all programming applications - choosing correct data types is fundamental to efficient plc programming.
Core Advantages for Temperature Control:
- Memory optimization: Critical for Temperature Control when handling intermediate control logic
- Type safety: Critical for Temperature Control when handling intermediate control logic
- Better organization: Critical for Temperature Control when handling intermediate control logic
- Improved performance: Critical for Temperature Control when handling intermediate control logic
- Enhanced maintainability: Critical for Temperature Control when handling intermediate control logic
Why Data Types Fits Temperature Control:
Temperature Control systems in Process Control typically involve:
- Sensors: RTDs (PT100/PT1000) for high-accuracy measurements, Thermocouples (J, K, T types) for high-temperature applications, Infrared pyrometers for non-contact measurement
- Actuators: SCR (thyristor) power controllers for electric heaters, Solid-state relays for on/off heating control, Proportional control valves for steam or thermal fluid
- Complexity: Intermediate with challenges including Long thermal time constants making tuning difficult
Control Strategies for Temperature Control:
- pid: Standard PID control with proportional, integral, and derivative terms tuned for the thermal process dynamics
- cascade: Master temperature loop outputs to slave heater/cooler control loop for tighter control
- ratio: Maintain temperature ratio between zones for gradient applications
Programming Fundamentals in Data Types:
Data Types in VisiLogic / UniLogic follows these key principles:
1. Structure: Data Types organizes code with type safety
2. Execution: Scan cycle integration ensures 4 sensor inputs are processed reliably
3. Data Handling: Proper data types for 5 actuator control signals
Best Practices for Data Types:
- Use smallest data type that accommodates the value range
- Use REAL for analog values that need decimal precision
- Create UDTs for frequently repeated data patterns
- Use meaningful names for array indices via constants
- Document units in comments (e.g., // Temperature in tenths of degrees)
Common Mistakes to Avoid:
- Using INT for values that exceed 32767
- Losing precision when converting REAL to INT
- Array index out of bounds causing memory corruption
- Not handling negative numbers correctly with unsigned types
Typical Applications:
1. Recipe management: Directly applicable to Temperature Control
2. Data logging: Related control patterns
3. Complex calculations: Related control patterns
4. System configuration: Related control patterns
Understanding these fundamentals prepares you to implement effective Data Types solutions for Temperature Control using Unitronics VisiLogic / UniLogic.
Implementing Temperature Control with Data Types
Industrial temperature control systems use PLCs to regulate process temperatures in manufacturing, food processing, chemical processing, and other applications. These systems maintain precise temperature setpoints through heating and cooling control while ensuring product quality and energy efficiency.
This walkthrough demonstrates practical implementation using Unitronics VisiLogic / UniLogic and Data Types programming.
System Requirements:
A typical Temperature Control implementation includes:
Input Devices (Sensors):
1. RTDs (PT100/PT1000) for high-accuracy measurements: Critical for monitoring system state
2. Thermocouples (J, K, T types) for high-temperature applications: Critical for monitoring system state
3. Infrared pyrometers for non-contact measurement: Critical for monitoring system state
4. Thermistors for fast response applications: Critical for monitoring system state
5. Thermal imaging cameras for surface temperature monitoring: Critical for monitoring system state
Output Devices (Actuators):
1. SCR (thyristor) power controllers for electric heaters: Primary control output
2. Solid-state relays for on/off heating control: Supporting control function
3. Proportional control valves for steam or thermal fluid: Supporting control function
4. Solenoid valves for cooling water or refrigerant: Supporting control function
5. Variable frequency drives for cooling fan control: Supporting control function
Control Equipment:
- Electric resistance heaters (cartridge, band, strip)
- Steam injection systems
- Thermal fluid (hot oil) systems
- Refrigeration and chiller systems
Control Strategies for Temperature Control:
- pid: Standard PID control with proportional, integral, and derivative terms tuned for the thermal process dynamics
- cascade: Master temperature loop outputs to slave heater/cooler control loop for tighter control
- ratio: Maintain temperature ratio between zones for gradient applications
Implementation Steps:
Step 1: Characterize thermal system dynamics (time constants, dead time)
In VisiLogic / UniLogic, characterize thermal system dynamics (time constants, dead time).
Step 2: Select appropriate sensor type and placement for representative measurement
In VisiLogic / UniLogic, select appropriate sensor type and placement for representative measurement.
Step 3: Size heating and cooling capacity for worst-case load conditions
In VisiLogic / UniLogic, size heating and cooling capacity for worst-case load conditions.
Step 4: Implement PID control with appropriate sample time (typically 10x faster than process time constant)
In VisiLogic / UniLogic, implement pid control with appropriate sample time (typically 10x faster than process time constant).
Step 5: Add output limiting and anti-windup for safe operation
In VisiLogic / UniLogic, add output limiting and anti-windup for safe operation.
Step 6: Program ramp/soak profiles if required
In VisiLogic / UniLogic, program ramp/soak profiles if required.
Unitronics Function Design:
Function block design in Unitronics uses user-defined FBs in UniLogic (more limited in VisiLogic). Extensive vendor-provided helper FBs cover common tasks (PID, motion, communication, HMI utilities). OEM machine builders typically maintain private FB libraries for their common machine patterns, though code reuse is less mature than in mainstream PLC ecosystems.
Common Challenges and Solutions:
1. Long thermal time constants making tuning difficult
- Solution: Data Types addresses this through Memory optimization.
2. Transport delay (dead time) causing instability
- Solution: Data Types addresses this through Type safety.
3. Non-linear response at different temperature ranges
- Solution: Data Types addresses this through Better organization.
4. Sensor placement affecting measurement accuracy
- Solution: Data Types addresses this through Improved performance.
Safety Considerations:
- Independent high-limit safety thermostats (redundant to PLC)
- Watchdog timers for heater control validity
- Safe-state definition on controller failure (heaters off)
- Thermal fuse backup for runaway conditions
- Proper ventilation for combustible atmospheres
Performance Metrics:
- Scan Time: Optimize for 4 inputs and 5 outputs
- Memory Usage: Efficient data structures for Jazz 2 capabilities
- Response Time: Meeting Process Control requirements for Temperature Control
Unitronics Diagnostic Tools:
UniLogic (current) and VisiLogic (legacy) integrated debuggers with breakpoints,Built-in simulator covering PLC logic, HMI screens, alarms, recipes, and data tables,Web visualisation for UniStream — remote HMI viewing without additional software,SD card logging with PC-side export tools for offline trend analysis,Modbus RTU/TCP transaction logging built into the IDE,Controller status monitor — CPU load, scan time, memory usage,HMI event logger capturing operator actions for audit purposes,CAN bus diagnostic tools for CANopen-equipped models,Remote support tool — Unitronics' own screen-sharing for technical support,User community forum with active troubleshooting discussions
Unitronics's VisiLogic / UniLogic provides tools for performance monitoring and optimization, essential for achieving the 2-3 weeks development timeline while maintaining code quality.
Unitronics Data Types Example for Temperature Control
Complete working example demonstrating Data Types implementation for Temperature Control using Unitronics VisiLogic / UniLogic. Follows Unitronics naming conventions. Tested on Jazz 2 hardware.
// Unitronics VisiLogic / UniLogic - Temperature Control Control
// Data Types Implementation for Process Control
// Unitronics projects use IDE-managed tag names rather than ra
// ============================================
// Variable Declarations
// ============================================
VAR
bEnable : BOOL := FALSE;
bEmergencyStop : BOOL := FALSE;
rThermocouplesKtypeJtype : REAL;
rHeatingelements : REAL;
END_VAR
// ============================================
// Input Conditioning - RTDs (PT100/PT1000) for high-accuracy measurements
// ============================================
// Standard input processing
IF rThermocouplesKtypeJtype > 0.0 THEN
bEnable := TRUE;
END_IF;
// ============================================
// Safety Interlock - Independent high-limit safety thermostats (redundant to PLC)
// ============================================
IF bEmergencyStop THEN
rHeatingelements := 0.0;
bEnable := FALSE;
END_IF;
// ============================================
// Main Temperature Control Control Logic
// ============================================
IF bEnable AND NOT bEmergencyStop THEN
// Industrial temperature control systems use PLCs to regulate
rHeatingelements := rThermocouplesKtypeJtype * 1.0;
// Process monitoring
// Add specific control logic here
ELSE
rHeatingelements := 0.0;
END_IF;Code Explanation:
- 1.Data Types structure optimized for Temperature Control in Process Control applications
- 2.Input conditioning handles RTDs (PT100/PT1000) for high-accuracy measurements signals
- 3.Safety interlock ensures Independent high-limit safety thermostats (redundant to PLC) always takes priority
- 4.Main control implements Industrial temperature control systems u
- 5.Code runs every scan cycle on Jazz 2 (typically 5-20ms)
Best Practices
- ✓Follow Unitronics naming conventions: Unitronics projects use IDE-managed tag names rather than raw memory addressing.
- ✓Unitronics function design: Function block design in Unitronics uses user-defined FBs in UniLogic (more limi
- ✓Data organization: Unitronics uses its own tag database concept rather than IEC-standard data block
- ✓Data Types: Use smallest data type that accommodates the value range
- ✓Data Types: Use REAL for analog values that need decimal precision
- ✓Data Types: Create UDTs for frequently repeated data patterns
- ✓Temperature Control: Sample at 1/10 of the process time constant minimum
- ✓Temperature Control: Use derivative on PV, not error, for temperature control
- ✓Temperature Control: Start with conservative tuning and tighten gradually
- ✓Debug with VisiLogic / UniLogic: Use the built-in simulator to reproduce issues before hardware visit
- ✓Safety: Independent high-limit safety thermostats (redundant to PLC)
- ✓Use VisiLogic / UniLogic simulation tools to test Temperature Control logic before deployment
Common Pitfalls to Avoid
- ⚠Data Types: Using INT for values that exceed 32767
- ⚠Data Types: Losing precision when converting REAL to INT
- ⚠Data Types: Array index out of bounds causing memory corruption
- ⚠Unitronics common error: VisiLogic-to-UniLogic migration issues — not all projects convert cleanly
- ⚠Temperature Control: Long thermal time constants making tuning difficult
- ⚠Temperature Control: Transport delay (dead time) causing instability
- ⚠Neglecting to validate RTDs (PT100/PT1000) for high-accuracy measurements leads to control errors
- ⚠Insufficient comments make Data Types programs unmaintainable over time
Related Certifications
Mastering Data Types for Temperature Control applications using Unitronics VisiLogic / UniLogic requires understanding both the platform's capabilities and the specific demands of Process Control. This guide has provided comprehensive coverage of implementation strategies, working code examples, best practices, and common pitfalls to help you succeed with intermediate Temperature Control projects.
Unitronics's 1% market share and moderate - us small-integrator market, oem machines, building automation demonstrate the platform's capability for demanding applications. The platform excels in Process Control applications where Temperature Control reliability is critical.
By following the practices outlined in this guide—from proper program structure and Data Types best practices to Unitronics-specific optimizations—you can deliver reliable Temperature Control systems that meet Process Control requirements.
Next Steps for Professional Development:
1. Certification: Pursue Unitronics Certified Integrator to validate your Unitronics expertise
2. Advanced Training: Consider UniLogic Developer Training for specialized Process Control applications
3. Hands-on Practice: Build Temperature Control projects using Jazz 2 hardware
4. Stay Current: Follow VisiLogic / UniLogic updates and new Data Types features
Data Types Foundation:
PLC data types define how values are stored, their valid ranges, and operations that can be performed. Proper type selection ensures accuracy and memo...
The 2-3 weeks typical timeline for Temperature Control projects will decrease as you gain experience with these patterns and techniques. Remember: Sample at 1/10 of the process time constant minimum
For further learning, explore related topics including Data logging, Plastic molding machines, and Unitronics platform-specific features for Temperature Control optimization.