Learning to implement Function Blocks for Temperature Control using INVT's INVT Workshop / AutoStudio 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.
INVT has established itself as Moderate in HVAC, water treatment, textiles, basic process equipment, and OEM machines paired with INVT drives, making it a strategic choice for Temperature Control applications. With <1% global global market share and 5 popular PLC families including the IVC1 and IVC2, INVT provides the robust platform needed for intermediate complexity projects like Temperature Control.
The Function Blocks approach is particularly well-suited for Temperature Control because process control, continuous operations, modular programming, and signal flow visualization. This combination allows you to leverage visual representation of signal flow 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 INVT Workshop / AutoStudio, 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 INVT Function Blocks programming.
INVT INVT Workshop / AutoStudio for Temperature Control
INVT Workshop and AutoStudio are the two programming tools for the IVC-series PLCs (IVC1, IVC2, IVC3) and the AX-series (AX70 etc.) respectively. The core IDE feel is FX-style — ladder, IL, and SFC editors with soft-element tables and offline simulator support — and the instruction set borrows from Mitsubishi FX conventions. INVT's heritage is in drives (variable-frequency and servo) rather than PLCs, and the engineering tools reflect that bias: drive-PLC integration is unusually clean, with a u...
Platform Strengths for Temperature Control:
- Excellent price-performance for combined PLC + drive systems
- Free programming software with simulator
- Compact CPUs with built-in pulse outputs and PID
- Strong drives heritage — tight VFD/servo integration
Unique ${brand.software} Features:
- Free Workshop / AutoStudio IDE with offline simulator
- FX-style instruction set easing migration
- Tight integration with INVT VFDs and servo drives
- Unified scope / trace across PLC and drive parameters
Key Capabilities:
The INVT Workshop / AutoStudio environment excels at Temperature Control applications through its excellent price-performance for combined plc + drive systems. 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
INVT's controller families for Temperature Control include:
- IVC1: Suitable for intermediate Temperature Control applications
- IVC2: Suitable for intermediate Temperature Control applications
- IVC3: Suitable for intermediate Temperature Control applications
- AX series: Suitable for intermediate Temperature Control applications
Hardware Selection Guidance:
IVC1 covers entry compact applications, IVC2 / IVC3 are mid-range with extended I/O and Ethernet (IVC3-Ethernet variants), AX70 represents INVT's higher-tier compact-modular line with motion features. Choice usually mirrors the drive size — small VFDs pair with IVC1; AX70 fits where servo motion and EtherCAT-like buses are required....
Industry Recognition:
Moderate in HVAC, water treatment, textiles, basic process equipment, and OEM machines paired with INVT drives. Limited Tier 1 presence; common in Chinese aftermarket fixturing where INVT VFDs are already specified....
Investment Considerations:
With $ pricing, INVT positions itself in the value 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 Function Blocks for Temperature Control
Function Block Diagram (FBD) is a graphical programming language where functions and function blocks are represented as boxes connected by signal lines. Data flows from left to right through the network.
Execution Model:
Blocks execute based on data dependencies - a block executes only when all its inputs are available. Networks execute top to bottom when dependencies allow.
Core Advantages for Temperature Control:
- Visual representation of signal flow: Critical for Temperature Control when handling intermediate control logic
- Good for modular programming: Critical for Temperature Control when handling intermediate control logic
- Reusable components: Critical for Temperature Control when handling intermediate control logic
- Excellent for process control: Critical for Temperature Control when handling intermediate control logic
- Good for continuous operations: Critical for Temperature Control when handling intermediate control logic
Why Function Blocks 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 Function Blocks:
StandardBlocks:
- logic: AND, OR, XOR, NOT - Boolean logic operations
- comparison: EQ, NE, LT, GT, LE, GE - Compare values
- math: ADD, SUB, MUL, DIV, MOD - Arithmetic operations
TimersCounters:
- ton: Timer On-Delay - Output turns ON after preset time
- tof: Timer Off-Delay - Output turns OFF after preset time
- tp: Pulse Timer - Output pulses for preset time
Connections:
- wires: Connect output pins to input pins to pass data
- branches: One output can connect to multiple inputs
- feedback: Outputs can feed back to inputs for state machines
Best Practices for Function Blocks:
- Arrange blocks for clear left-to-right data flow
- Use consistent spacing and alignment for readability
- Label all inputs and outputs with meaningful names
- Create custom FBs for frequently repeated logic patterns
- Minimize wire crossings by careful block placement
Common Mistakes to Avoid:
- Creating feedback loops without proper initialization
- Connecting incompatible data types
- Not considering execution order dependencies
- Overcrowding networks making them hard to read
Typical Applications:
1. HVAC control: Directly applicable to Temperature Control
2. Temperature control: Related control patterns
3. Flow control: Related control patterns
4. Batch processing: Related control patterns
Understanding these fundamentals prepares you to implement effective Function Blocks solutions for Temperature Control using INVT INVT Workshop / AutoStudio.
Implementing Temperature Control with Function Blocks
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 INVT INVT Workshop / AutoStudio and Function Blocks 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 INVT Workshop / AutoStudio, characterize thermal system dynamics (time constants, dead time).
Step 2: Select appropriate sensor type and placement for representative measurement
In INVT Workshop / AutoStudio, select appropriate sensor type and placement for representative measurement.
Step 3: Size heating and cooling capacity for worst-case load conditions
In INVT Workshop / AutoStudio, 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 INVT Workshop / AutoStudio, 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 INVT Workshop / AutoStudio, add output limiting and anti-windup for safe operation.
Step 6: Program ramp/soak profiles if required
In INVT Workshop / AutoStudio, program ramp/soak profiles if required.
INVT Function Design:
P-label subroutines plus a small library of INVT-supplied drive-control FBs that wrap the proprietary Modbus parameter map. Reuse beyond the supplied library is open-coded.
Common Challenges and Solutions:
1. Long thermal time constants making tuning difficult
- Solution: Function Blocks addresses this through Visual representation of signal flow.
2. Transport delay (dead time) causing instability
- Solution: Function Blocks addresses this through Good for modular programming.
3. Non-linear response at different temperature ranges
- Solution: Function Blocks addresses this through Reusable components.
4. Sensor placement affecting measurement accuracy
- Solution: Function Blocks addresses this through Excellent for process control.
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 IVC1 capabilities
- Response Time: Meeting Process Control requirements for Temperature Control
INVT Diagnostic Tools:
Workshop online monitoring with rung-state highlighting,Combined PLC + drive scope / trace tool,Soft-element watch table,Drive-parameter live-monitor view,Modbus RTU / TCP communication analyzer,Built-in offline simulator,Distributor loaner CPU/drive pairs for triage,INVT community forum (Chinese-dominant) for protocol-specific issues
INVT's INVT Workshop / AutoStudio provides tools for performance monitoring and optimization, essential for achieving the 2-3 weeks development timeline while maintaining code quality.
INVT Function Blocks Example for Temperature Control
Complete working example demonstrating Function Blocks implementation for Temperature Control using INVT INVT Workshop / AutoStudio. Follows INVT naming conventions. Tested on IVC1 hardware.
(* INVT INVT Workshop / AutoStudio - Temperature Control Control *)
(* Reusable Function Blocks Implementation *)
(* P-label subroutines plus a small library of INVT-supplied dr *)
FUNCTION_BLOCK FB_TEMPERATURE_CONTROL_Controller
VAR_INPUT
bEnable : BOOL; (* Enable control *)
bReset : BOOL; (* Fault reset *)
rProcessValue : REAL; (* RTDs (PT100/PT1000) for high-accuracy measurements *)
rSetpoint : REAL := 100.0; (* Target value *)
bEmergencyStop : BOOL; (* Safety input *)
END_VAR
VAR_OUTPUT
rControlOutput : REAL; (* SCR (thyristor) power controllers for electric heaters *)
bRunning : BOOL; (* Process active *)
bComplete : BOOL; (* Cycle complete *)
bFault : BOOL; (* Fault status *)
nFaultCode : INT; (* Diagnostic code *)
END_VAR
VAR
(* Internal Function Blocks *)
fbSafety : FB_SafetyMonitor; (* Safety logic *)
fbRamp : FB_RampGenerator; (* Soft start/stop *)
fbPID : FB_PIDController; (* Process control *)
fbDiag : FB_Diagnostics; (* M-flag banks plus drive-fault flags read via Modbus parameter mapping; combined alarm rollup to HMI tag. *)
(* Internal State *)
eInternalState : E_ControlState;
tonWatchdog : TON;
END_VAR
(* Safety Monitor - Independent high-limit safety thermostats (redundant to PLC) *)
fbSafety(
Enable := bEnable,
EmergencyStop := bEmergencyStop,
ProcessValue := rProcessValue,
HighLimit := rSetpoint * 1.2,
LowLimit := rSetpoint * 0.1
);
(* Main Control Logic *)
IF fbSafety.SafeToRun THEN
(* Ramp Generator - Prevents startup surge *)
fbRamp(
Enable := bEnable,
TargetValue := rSetpoint,
RampRate := 20.0, (* Process Control rate *)
CurrentValue => rSetpoint
);
(* PID Controller - [object Object] *)
fbPID(
Enable := fbRamp.InPosition,
ProcessValue := rProcessValue,
Setpoint := fbRamp.CurrentValue,
Kp := 1.0,
Ki := 0.1,
Kd := 0.05,
OutputMin := 0.0,
OutputMax := 100.0
);
rControlOutput := fbPID.Output;
bRunning := TRUE;
bFault := FALSE;
nFaultCode := 0;
ELSE
(* Safe State - Watchdog timers for heater control validity *)
rControlOutput := 0.0;
bRunning := FALSE;
bFault := NOT bEnable; (* Only fault if not intentional stop *)
nFaultCode := fbSafety.FaultCode;
END_IF;
(* Diagnostics - Offloaded to HMI / SCADA via Modbus; some scope traces savable from Workshop for one-off captures. *)
fbDiag(
ProcessRunning := bRunning,
FaultActive := bFault,
ProcessValue := rProcessValue,
ControlOutput := rControlOutput
);
(* Watchdog - Detects frozen control *)
tonWatchdog(IN := bRunning AND NOT fbPID.OutputChanging, PT := T#10S);
IF tonWatchdog.Q THEN
bFault := TRUE;
nFaultCode := 99; (* Watchdog fault *)
END_IF;
(* Reset Logic *)
IF bReset AND NOT bEmergencyStop THEN
bFault := FALSE;
nFaultCode := 0;
fbDiag.ClearAlarms();
END_IF;
END_FUNCTION_BLOCKCode Explanation:
- 1.Encapsulated function block follows P-label subroutines plus a small library - reusable across Process Control projects
- 2.FB_SafetyMonitor provides Independent high-limit safety thermostats (redundant to PLC) including high/low limits
- 3.FB_RampGenerator prevents startup issues common in Temperature Control systems
- 4.FB_PIDController tuned for Process Control: Kp=1.0, Ki=0.1
- 5.Watchdog timer detects frozen control - critical for intermediate Temperature Control reliability
- 6.Diagnostic function block enables Offloaded to HMI / SCADA via Modbus; some scope traces savable from Workshop for one-off captures. and M-flag banks plus drive-fault flags read via Modbus parameter mapping; combined alarm rollup to HMI tag.
Best Practices
- ✓Follow INVT naming conventions: Raw FX-style addressing dominates. Symbolic naming is supported but rarely used
- ✓INVT function design: P-label subroutines plus a small library of INVT-supplied drive-control FBs that
- ✓Data organization: No structured DB; D / HD register banks with engineer-documented range conventio
- ✓Function Blocks: Arrange blocks for clear left-to-right data flow
- ✓Function Blocks: Use consistent spacing and alignment for readability
- ✓Function Blocks: Label all inputs and outputs with meaningful names
- ✓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 INVT Workshop / AutoStudio: Use the combined scope to confirm whether a fault is in PLC logic or i
- ✓Safety: Independent high-limit safety thermostats (redundant to PLC)
- ✓Use INVT Workshop / AutoStudio simulation tools to test Temperature Control logic before deployment
Common Pitfalls to Avoid
- ⚠Function Blocks: Creating feedback loops without proper initialization
- ⚠Function Blocks: Connecting incompatible data types
- ⚠Function Blocks: Not considering execution order dependencies
- ⚠INVT common error: Drive-parameter mapping desync after firmware update on attached VFD
- ⚠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 Function Blocks programs unmaintainable over time
Related Certifications
Mastering Function Blocks for Temperature Control applications using INVT INVT Workshop / AutoStudio 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.
INVT's <1% global market share and moderate in hvac, water treatment, textiles, basic process equipment, and oem machines paired with invt drives 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 Function Blocks best practices to INVT-specific optimizations—you can deliver reliable Temperature Control systems that meet Process Control requirements.
Next Steps for Professional Development:
1. Certification: Pursue INVT distributor training to validate your INVT expertise
2. Advanced Training: Consider Drive-PLC integration certificates for specialized Process Control applications
3. Hands-on Practice: Build Temperature Control projects using IVC1 hardware
4. Stay Current: Follow INVT Workshop / AutoStudio updates and new Function Blocks features
Function Blocks Foundation:
Function Block Diagram (FBD) is a graphical programming language where functions and function blocks are represented as boxes connected by signal line...
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 Temperature control, Plastic molding machines, and INVT platform-specific features for Temperature Control optimization.