Control

MEASURING PRINCIPLE

Positioning and actuation

A positioner compares the 4–20 mA setpoint with stem position and drives the actuator until they match.

PRINCIPLE · LIVE SIGNAL13.9mA

HOW IT WORKS

See the principle in action

Move the slider to change the process variable and watch the signal respond.

Positioning and actuation

SETPOINT SIGNAL
12.0 mA

OUTPUT
12.0 mA

ADJUST SETPOINT SIGNAL

The controller sends a 4–20 mA setpoint.
The positioner compares it with the measured stem position.
It drives the actuator until position equals setpoint, correcting friction and air-pressure effects.

AT A GLANCE

Strengths and limits

STRENGTHS

Closes the loop on valve travel, adds diagnostics

LIMITS

Requires clean instrument air for pneumatic types

INSTRUMENTS

Instruments using this principle

CV-310

Control

Smart Valve Positioner

HART positioner with partial-stroke testing and valve diagnostics.

ACCURACY

Resolution 0.1 %

PROTECTION

IP66

CV-410

Control

Electric Quarter-Turn Actuator

24 V or 230 V actuator with Modbus control and position feedback.

ACCURACY

Positioning ±1 %

PROTECTION

IP67

APPLICATIONS

Where this principle is the answer

APPLICATION

Wastewater pH dosing control

pH must be held in a narrow band while dosing chemicals, against fouling and flow changes.

Read the application →

Articles and downloads

Technical article

Why valve positioners matter

Open →

FAQ

Common questions

RFQ

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Positioning and actuation

See the principle in action

Strengths and limits

Instruments using this principle

Smart Valve Positioner

Electric Quarter-Turn Actuator

Where this principle is the answer

Wastewater pH dosing control

Articles and downloads

Why valve positioners matter

Common questions

Why add a positioner to a control valve?

Specify the right instrument