Learning to implement Structured Text for Sensor Integration using Unitronics's VisiLogic / UniLogic is an essential skill for PLC programmers working in Universal. 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 Sensor Integration 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 beginner to intermediate complexity projects like Sensor Integration.
The Structured Text approach is particularly well-suited for Sensor Integration because complex calculations, data manipulation, advanced control algorithms, and when code reusability is important. This combination allows you to leverage powerful for complex logic while managing the typical challenges of Sensor Integration, including signal conditioning and sensor calibration.
Throughout this guide, you'll discover step-by-step implementation strategies, working code examples tested on VisiLogic / UniLogic, and industry best practices specific to Universal. Whether you're programming your first Sensor Integration system or transitioning from another PLC platform, this guide provides the practical knowledge you need to succeed with Unitronics Structured Text programming.
Unitronics VisiLogic / UniLogic for Sensor Integration
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 Sensor Integration:
- 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 Sensor Integration applications through its combined plc + hmi in one unit reduces panel cost. This is particularly valuable when working with the 5 sensor types typically found in Sensor Integration systems, including Analog sensors (4-20mA, 0-10V), Digital sensors (NPN, PNP), Smart sensors (IO-Link).
Unitronics's controller families for Sensor Integration include:
- Jazz 2: Suitable for beginner to intermediate Sensor Integration applications
- Samba 7": Suitable for beginner to intermediate Sensor Integration applications
- Vision V350: Suitable for beginner to intermediate Sensor Integration applications
- Vision V570: Suitable for beginner to intermediate Sensor Integration 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 Sensor Integration projects requiring beginner skill levels and 1-2 weeks development time, the total investment includes hardware, software licensing, training, and ongoing support.
Understanding Structured Text for Sensor Integration
Structured Text (ST) is a high-level, text-based programming language defined in IEC 61131-3. It resembles Pascal and provides powerful constructs for complex algorithms, calculations, and data manipulation.
Execution Model:
Code executes sequentially from top to bottom within each program unit. Variables maintain state between scan cycles unless explicitly reset.
Core Advantages for Sensor Integration:
- Powerful for complex logic: Critical for Sensor Integration when handling beginner to intermediate control logic
- Excellent code reusability: Critical for Sensor Integration when handling beginner to intermediate control logic
- Compact code representation: Critical for Sensor Integration when handling beginner to intermediate control logic
- Good for algorithms and calculations: Critical for Sensor Integration when handling beginner to intermediate control logic
- Familiar to software developers: Critical for Sensor Integration when handling beginner to intermediate control logic
Why Structured Text Fits Sensor Integration:
Sensor Integration systems in Universal typically involve:
- Sensors: Discrete sensors (proximity, photoelectric, limit switches), Analog sensors (4-20mA, 0-10V transmitters), Temperature sensors (RTD, thermocouple, thermistor)
- Actuators: Not applicable - focus on input processing
- Complexity: Beginner to Intermediate with challenges including Electrical noise affecting analog signals
Programming Fundamentals in Structured Text:
Variables:
- declaration: VAR / VAR_INPUT / VAR_OUTPUT / VAR_IN_OUT / VAR_GLOBAL sections
- initialization: Variables can be initialized at declaration: Counter : INT := 0;
- constants: VAR CONSTANT section for read-only values
Operators:
- arithmetic: + - * / MOD (modulo)
- comparison: = <> < > <= >=
- logical: AND OR XOR NOT
ControlStructures:
- if: IF condition THEN statements; ELSIF condition THEN statements; ELSE statements; END_IF;
- case: CASE selector OF value1: statements; value2: statements; ELSE statements; END_CASE;
- for: FOR index := start TO end BY step DO statements; END_FOR;
Best Practices for Structured Text:
- Use meaningful variable names with consistent naming conventions
- Initialize all variables at declaration to prevent undefined behavior
- Use enumerated types for state machines instead of magic numbers
- Break complex expressions into intermediate variables for readability
- Use functions for reusable calculations and function blocks for stateful operations
Common Mistakes to Avoid:
- Using = instead of := for assignment (= is comparison)
- Forgetting semicolons at end of statements
- Integer division truncation - use REAL for decimal results
- Infinite loops from incorrect WHILE/REPEAT conditions
Typical Applications:
1. PID control: Directly applicable to Sensor Integration
2. Recipe management: Related control patterns
3. Statistical calculations: Related control patterns
4. Data logging: Related control patterns
Understanding these fundamentals prepares you to implement effective Structured Text solutions for Sensor Integration using Unitronics VisiLogic / UniLogic.
Implementing Sensor Integration with Structured Text
Sensor integration involves connecting various measurement devices to PLCs for process monitoring and control. Proper sensor selection, wiring, signal conditioning, and programming ensure reliable data for control decisions.
This walkthrough demonstrates practical implementation using Unitronics VisiLogic / UniLogic and Structured Text programming.
System Requirements:
A typical Sensor Integration implementation includes:
Input Devices (Sensors):
1. Discrete sensors (proximity, photoelectric, limit switches): Critical for monitoring system state
2. Analog sensors (4-20mA, 0-10V transmitters): Critical for monitoring system state
3. Temperature sensors (RTD, thermocouple, thermistor): Critical for monitoring system state
4. Pressure sensors (gauge, differential, absolute): Critical for monitoring system state
5. Level sensors (ultrasonic, radar, capacitive, float): Critical for monitoring system state
Output Devices (Actuators):
1. Not applicable - focus on input processing: Primary control output
Control Strategies for Sensor Integration:
1. Primary Control: Integrating various sensors with PLCs for data acquisition, analog signal processing, and digital input handling.
2. Safety Interlocks: Preventing Signal conditioning
3. Error Recovery: Handling Sensor calibration
Implementation Steps:
Step 1: Select sensor appropriate for process conditions (temperature, pressure, media)
In VisiLogic / UniLogic, select sensor appropriate for process conditions (temperature, pressure, media).
Step 2: Design wiring with proper shielding, grounding, and routing
In VisiLogic / UniLogic, design wiring with proper shielding, grounding, and routing.
Step 3: Configure input module for sensor type and resolution
In VisiLogic / UniLogic, configure input module for sensor type and resolution.
Step 4: Develop scaling routine with calibration parameters
In VisiLogic / UniLogic, develop scaling routine with calibration parameters.
Step 5: Implement signal conditioning (filtering, rate limiting)
In VisiLogic / UniLogic, implement signal conditioning (filtering, rate limiting).
Step 6: Add fault detection with appropriate response
In VisiLogic / UniLogic, add fault detection with appropriate response.
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. Electrical noise affecting analog signals
- Solution: Structured Text addresses this through Powerful for complex logic.
2. Sensor drift requiring periodic recalibration
- Solution: Structured Text addresses this through Excellent code reusability.
3. Ground loops causing measurement errors
- Solution: Structured Text addresses this through Compact code representation.
4. Response time limitations for fast processes
- Solution: Structured Text addresses this through Good for algorithms and calculations.
Safety Considerations:
- Use intrinsically safe sensors and barriers in hazardous areas
- Implement redundant sensors for safety-critical measurements
- Design for fail-safe operation on sensor loss
- Provide regular sensor calibration for safety systems
- Document measurement uncertainty for safety calculations
Performance Metrics:
- Scan Time: Optimize for 5 inputs and 1 outputs
- Memory Usage: Efficient data structures for Jazz 2 capabilities
- Response Time: Meeting Universal requirements for Sensor Integration
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 1-2 weeks development timeline while maintaining code quality.
Unitronics Structured Text Example for Sensor Integration
Complete working example demonstrating Structured Text implementation for Sensor Integration using Unitronics VisiLogic / UniLogic. Follows Unitronics naming conventions. Tested on Jazz 2 hardware.
(* Unitronics VisiLogic / UniLogic - Sensor Integration Control *)
(* Structured Text Implementation for Universal *)
(* Unitronics projects use IDE-managed tag names rather than raw memory a *)
PROGRAM PRG_SENSOR_INTEGRATION_Control
VAR
(* State Machine Variables *)
eState : E_SENSOR_INTEGRATION_States := IDLE;
bEnable : BOOL := FALSE;
bFaultActive : BOOL := FALSE;
(* Timers *)
tonDebounce : TON;
tonProcessTimeout : TON;
tonFeedbackCheck : TON;
(* Counters *)
ctuCycleCounter : CTU;
(* Process Variables *)
rAnalogsensors420mA010V : REAL := 0.0;
rNotapplicablefocusoninputprocessing : REAL := 0.0;
rSetpoint : REAL := 100.0;
END_VAR
VAR CONSTANT
(* Universal Process Parameters *)
C_DEBOUNCE_TIME : TIME := T#500MS;
C_PROCESS_TIMEOUT : TIME := T#30S;
C_BATCH_SIZE : INT := 50;
END_VAR
(* Input Conditioning *)
tonDebounce(IN := bStartButton, PT := C_DEBOUNCE_TIME);
bEnable := tonDebounce.Q AND NOT bEmergencyStop AND bSafetyOK;
(* Main State Machine - Pattern: State machines are commonly implemented *)
CASE eState OF
IDLE:
rNotapplicablefocusoninputprocessing := 0.0;
ctuCycleCounter(RESET := TRUE);
IF bEnable AND rAnalogsensors420mA010V > 0.0 THEN
eState := STARTING;
END_IF;
STARTING:
(* Ramp up output - Gradual start *)
rNotapplicablefocusoninputprocessing := MIN(rNotapplicablefocusoninputprocessing + 5.0, rSetpoint);
IF rNotapplicablefocusoninputprocessing >= rSetpoint THEN
eState := RUNNING;
END_IF;
RUNNING:
(* Sensor Integration active - Sensor integration involves connecting various mea *)
tonProcessTimeout(IN := TRUE, PT := C_PROCESS_TIMEOUT);
ctuCycleCounter(CU := bCyclePulse, PV := C_BATCH_SIZE);
IF ctuCycleCounter.Q THEN
eState := COMPLETE;
ELSIF tonProcessTimeout.Q THEN
bFaultActive := TRUE;
eState := FAULT;
END_IF;
COMPLETE:
rNotapplicablefocusoninputprocessing := 0.0;
(* Log production data - Data logging uses UniLogic's Data Samplers — configured triggers (time-based or event-based) write structured records to Data Tables or SD card in CSV format. Exported files can be pushed via FTP or email. For cloud integration, UniCloud provides managed data ingestion. Simpler VisiLogic projects use HMI-triggered SD writes via custom ladder code. *)
eState := IDLE;
FAULT:
rNotapplicablefocusoninputprocessing := 0.0;
(* Alarm handling uses UniLogic's built-in Alarm Manager — configure alarm conditions in tables with severity, message text, and logging behaviour, and the engine handles detection, acknowledgement, history, and HMI display without custom code. VisiLogic uses a simpler alarm approach via HMI event handlers. *)
IF bFaultReset AND NOT bEmergencyStop THEN
bFaultActive := FALSE;
eState := IDLE;
END_IF;
END_CASE;
(* Safety Override - Always executes *)
IF bEmergencyStop OR NOT bSafetyOK THEN
rNotapplicablefocusoninputprocessing := 0.0;
eState := FAULT;
bFaultActive := TRUE;
END_IF;
END_PROGRAMCode Explanation:
- 1.Enumerated state machine (State machines are commonly implemented in ladder with step-counter registers or in ST using CASE structures with named state constants. UniLogic's HMI graphical bindings make state-to-screen visualisation straightforward — a single state variable drives both logic and operator screen transitions. SFC is not a primary language on Unitronics; state logic is typically CASE or ladder.) for clear Sensor Integration sequence control
- 2.Constants define Universal-specific parameters: cycle time 30s, batch size
- 3.Input conditioning with debounce timer prevents false triggers in industrial environment
- 4.STARTING state implements soft-start ramp - prevents mechanical shock
- 5.Process timeout detection identifies stuck conditions - critical for reliability
- 6.Safety override section executes regardless of state - Unitronics best practice for beginner to intermediate systems
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
- ✓Structured Text: Use meaningful variable names with consistent naming conventions
- ✓Structured Text: Initialize all variables at declaration to prevent undefined behavior
- ✓Structured Text: Use enumerated types for state machines instead of magic numbers
- ✓Sensor Integration: Document wire colors and termination points for maintenance
- ✓Sensor Integration: Use proper cold junction compensation for thermocouples
- ✓Sensor Integration: Provide test points for verification without disconnection
- ✓Debug with VisiLogic / UniLogic: Use the built-in simulator to reproduce issues before hardware visit
- ✓Safety: Use intrinsically safe sensors and barriers in hazardous areas
- ✓Use VisiLogic / UniLogic simulation tools to test Sensor Integration logic before deployment
Common Pitfalls to Avoid
- ⚠Structured Text: Using = instead of := for assignment (= is comparison)
- ⚠Structured Text: Forgetting semicolons at end of statements
- ⚠Structured Text: Integer division truncation - use REAL for decimal results
- ⚠Unitronics common error: VisiLogic-to-UniLogic migration issues — not all projects convert cleanly
- ⚠Sensor Integration: Electrical noise affecting analog signals
- ⚠Sensor Integration: Sensor drift requiring periodic recalibration
- ⚠Neglecting to validate Discrete sensors (proximity, photoelectric, limit switches) leads to control errors
- ⚠Insufficient comments make Structured Text programs unmaintainable over time
Related Certifications
Mastering Structured Text for Sensor Integration applications using Unitronics VisiLogic / UniLogic requires understanding both the platform's capabilities and the specific demands of Universal. This guide has provided comprehensive coverage of implementation strategies, working code examples, best practices, and common pitfalls to help you succeed with beginner to intermediate Sensor Integration 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 Universal applications where Sensor Integration reliability is critical.
By following the practices outlined in this guide—from proper program structure and Structured Text best practices to Unitronics-specific optimizations—you can deliver reliable Sensor Integration systems that meet Universal 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 Universal applications
3. Hands-on Practice: Build Sensor Integration projects using Jazz 2 hardware
4. Stay Current: Follow VisiLogic / UniLogic updates and new Structured Text features
Structured Text Foundation:
Structured Text (ST) is a high-level, text-based programming language defined in IEC 61131-3. It resembles Pascal and provides powerful constructs for...
The 1-2 weeks typical timeline for Sensor Integration projects will decrease as you gain experience with these patterns and techniques. Remember: Document wire colors and termination points for maintenance
For further learning, explore related topics including Recipe management, Process measurement, and Unitronics platform-specific features for Sensor Integration optimization.