Electric Actuator Control Modes: On-Off vs Modulating
Quick Comparison Table
| Feature | On-Off Control | Modulating Control |
|---|---|---|
| Operation | Fully open or fully closed | Any position between 0–100% |
| Control Signal | 2-wire (open/close) | 4–20mA, 0–10V, 2–10V |
| Positioning Accuracy | ±5–10% | ±0.5–2% |
| Typical Applications | Isolation, tank filling | Flow regulation, pressure control |
| Duty Cycle | Low (intermittent) | High (continuous) |
| Cost | Lower | Higher |
When to Choose On-Off Control
On-off electric actuators are ideal for applications requiring only open or closed positions.
| Application | Why On-Off |
|---|---|
| Tank filling | Stop when full, open when empty |
| Isolation valves | Fully sealed shut-off |
| Pump start/stop | Simple open/close logic |
| HVAC dampers | Basic air flow switching |
| Irrigation zones | Open or close per schedule |
Signal Types:
-
2-wire (open/close command)
-
3-wire (open/stop/close)
-
Normally open (NO) or normally closed (NC)
-
When to Choose Modulating Control
Modulating actuators provide precise position control for regulating flow, pressure, or temperature.
| Application | Why Modulating |
|---|---|
| Flow control loop | Adjust valve position to maintain setpoint |
| Pressure regulation | Fine-tune opening for stable pressure |
| Temperature control | Modulate hot/cold fluid mixing |
| Dosing systems | Precise chemical injection rate |
| Batching processes | Accurate fill volumes |
Signal Types:
-
4–20mA (most common)
-
0–10V DC
-
2–10V DC
-
Digital communication (Modbus, Profibus, HART)
Technical Specifications Comparison
| Parameter | On-Off Actuator | Modulating Actuator |
|---|---|---|
| Control signal | Dry contact / voltage | Analog (4–20mA) |
| Position feedback | Limit switches (2) | 4–20mA feedback |
| Deadband | Not applicable | Adjustable (0.5–5%) |
| Response time | Fast (full stroke) | Proportional (adjustable) |
| Motor type | Standard AC/DC | High resolution / servo |
| Encoder | Optional | Standard (potentiometer or encoder) |
| Positioner | No | Yes (integrated or external) |
| Typical accuracy | Full stroke only | ±0.5–1% |
Selection Decision Matrix
| Requirement | On-Off | Modulating |
|---|---|---|
| Need only open/closed | ✓ | |
| Need any intermediate position | ✓ | |
| Budget sensitive | ✓ | |
| Precise flow control required | ✓ | |
| Simple PLC with digital outputs | ✓ | |
| PLC with analog output card | ✓ | |
| High cycle frequency | ✓ | |
| Infrequent operation | ✓ |
Cost Comparison
| Factor | On-Off | Modulating |
|---|---|---|
| Actuator cost | $ | $$ – $$$ |
| Positioner cost | None | $ – $$ |
| Control wiring | 3–5 wires | 4–6 wires (shielded recommended) |
| PLC I/O cost | Low (digital) | Higher (analog) |
| Installation | Simple | More complex |
| Calibration | None | Required |
Common Mistakes to Avoid
| Mistake | Consequence | Solution |
|---|---|---|
| Using on-off for modulating duty | Shortened lifespan, poor control | Select modulating actuator |
| Using modulating for simple isolation | Overpaying for unneeded features | Use on-off actuator |
| Ignoring deadband settings | Hunting / oscillation | Adjust deadband properly |
| Wrong control signal type | Actuator won't respond | Match signal to actuator spec |
| Undersized actuator | Cannot achieve full stroke | Size torque properly |
Quick Selection Flowchart
Does the valve need intermediate positions?
│
├── NO → On-Off Actuator
│ - Simple open/close
│ - Lower cost
│ - Digital control
│
└── YES → Modulating Actuator
- 4–20mA / 0–10V signal
- Position feedback
- Higher accuracy
Need Help Selecting the Right Electric Actuator?
Our electric actuator range covers both on-off and modulating control:
| Series | Control Type | Torque Range | Signal Type |
|---|---|---|---|
| EA-OnOff Series | On-Off | 10–2000 Nm | Open/close command |
| EA-Mod Series | Modulating | 20–3000 Nm | 4–20mA / 0–10V |
| EA-Intelligent Series | Both | 50–5000 Nm | Configurable + Modbus |
Contact our application engineers for actuator sizing and selection support.
*Electric Actuator | On-Off Control | Modulating Control | Valve Automation | B2B Industrial Supplier*
Ivan (Mobile:+86-18968769287)
WhatsApp：+86-13579991606
Wechat:+86-18968769287
Website：www.kinko-flow.com
ZHEJIANG KINKO FLUID EQUIPMENT CO.,LTD
