Last revised: October 18, 2024
Reviewed by: Scott Orlosky, consulting engineer

Pump controllers monitor flow and/or level variables, and control a pump accordingly to maintain the desired levels. Pump control can include simply turning a pump on and off, or more advanced controls for pump speed, output pressure, etc. Many pump controllers include rate indication features, totalizer, data logger, and chart recorder capabilities. Products that provide level or pressure control are also available. Level controllers monitor, regulate, and control liquid or solid levels in a process. Pressure controllers accept inputs from pressure sensors, transmitters, gauges, and other devices. These pump controllers then adjust and control the pressure to maintain or achieve a desired level.  Some pump controllers are printed circuit boards (PCB) that can be plugged directly into a computer backplane. Others attach to a panel or bolt onto a chassis, wall, cabinet, or enclosure; mount in racks and include hardware such as rail guides, flanges, or tabs; or mount on a standard DIN rail. Benchtop or floor-standing pump controllers with a full casing or cabinet and an integral interface are also available.

Specifications

Specifications for pump controllers include number of inputs, number of outputs, input types, output types, and number of zones (if applicable).

The number of inputs equals the total number of signals sent to the controller.

The number of outputs equals the total number of outputs used to control, compensate or correct the process.

Input types include: direct current (DC) voltages, current loops, analog signals from resistors or potentiometers, frequency inputs, and switch or relay inputs.

Output types include analog voltages, current loops, switch or relay outputs, and pulses or frequencies.

Pump controllers can also send inputs or receive outputs in serial, parallel, Ethernet or other digital formats which indicate a process variable. Some pump controllers send or receive accept commands and inputs from information converted to an industrial fieldbus protocol such as CANbus, PROFIBUS^®, or SERCOS, or other industrial automation protocol. PROFIBUS is a registered trademark of PROFIBUS International. 

Pump controllers use different control techniques.

Limit control establishes set points or limits that, when reached cause the pump controller to send a signal to stop or start a process variable. 

Linear control matches a variable input signal with a correspondingly variable control signal. Signal conditioning, filtering, and amplification can be used to produce the proper output control signal.

Proportional, integral, and derivative (PID) control requires real-time system feedback.

Feedforward control provides direct-control compensation from the reference signal and can be open-loop or used in conjunction with more advanced PID control.

Fuzzy logic is a type of pump control in which variables can have imprecise values (as in partial truth) rather than a binary status (completely true or completely false). Pump controllers can also use advanced or nonlinear controls with algorithms such as neural networking and adaptive gain. 

Pump controllers differ in terms of media, user interface, and compliance.

Liquid, solids or powders, gases or air, and steam are media choices.

In terms of the user interface, pump controllers may include a digital front panel or have analog components such as knobs, switches, and meters. Computer-programmable, web-enabled, and Ethernet or network-ready devices are also available.

In terms of compliance, pump controllers that are destined for sale in the European marketplace should meet the requirements of the Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronics Equipment (WEEE) directives from the European Union (EU).

Pump Controller FAQs

What are the differences between on-off and modulating pump control systems?

Understanding the differences between on-off and modulating pump control systems is crucial for selecting the appropriate control method for an application. Here are the key distinctions:

Control Mechanism

On-Off Systems: These systems provide only two conditions: a given flow (or pressure) value or a zero value. Essentially, the pump is either fully on or fully off. A valve is either open or closed, and a pump driver is running or not.

Modulating Systems: These systems adjust the valve setting or pump speed to meet the current needs. The adjustment can be continuous and precise, allowing for more nuanced control of flow rate, pressure, or liquid level.

Operational Flexibility

On-Off Systems: Limited to binary operation, these systems are simpler but less flexible. They are suitable for applications where precise control is not critical and where the process can tolerate fluctuations between the on and off states.

Modulating Systems: Offer greater flexibility by continuously adjusting to the process requirements. This makes them suitable for applications requiring precise control and stability, such as maintaining a specific flow rate or pressure.

Complexity and Cost

On-Off Systems: Generally simpler and less expensive to implement. They require fewer components and less sophisticated control algorithms.

Modulating Systems: More complex and typically more expensive due to the need for advanced control algorithms and additional components to continuously adjust the system.

Energy Efficiency

On-Off Systems: Depends on the design. System can be optimized for a specific flow rate dictated by the full on requirements.

Modulating Systems: Design dependent. Pump is not always working at its optimum flow rate. Losses due to slippage or continuous operation at non-optimum speed can be more energy intensive.

Wear and Tear

On-Off Systems: Very design dependent. The actual on time of the pump is less if pumping from a tank, since it only runs long enough to fill and then shuts off.

Modulating Systems: Smoothing out the operation means that the actual run time of the pump is longer than an On-Off system. Operation should be designed to optimize the frequency and profile of start-stop cycles.

In general on-off pump control systems are simpler and less costly. They offer limited flexibility and since they run at a fixed speed they can be optimized for efficiency. Modulating pump control systems, on the other hand, provide precise control, and must be carefully designed to optimize energy efficiency, and reduce wear and tear, so should be used in more demanding applications.

How do pump controllers ensure compliance with RoHS and WEEE directives?

Pump controllers destined for sale in the European marketplace must comply with the Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronics Equipment (WEEE) directives from the European Union (EU). Here’s how they ensure compliance:

Material Restrictions (RoHS)

RoHS Directive: This directive restricts the use of specific hazardous materials found in electrical and electronic products. To comply, pump controllers must be manufactured without the use of certain substances, such as lead, mercury, cadmium, hexavalent chromium, and specific brominated flame retardants (PBB and PBDE).

Material Selection: Manufacturers select materials and components that meet RoHS requirements, ensuring that none of the restricted substances exceed the maximum concentration values set by the directive.

Testing and Certification: Pump controllers undergo rigorous testing to verify that they meet RoHS standards. Certification from accredited laboratories may be obtained to demonstrate compliance.

Waste Management (WEEE)

WEEE Directive: This directive aims to reduce electronic waste and promote the recycling and reuse of electrical and electronic equipment. Pump controllers must be designed and manufactured in a way that facilitates dismantling and recycling.

Design for Disassembly: Manufacturers design pump controllers with end-of-life considerations in mind, making it easier to disassemble and recycle components.

Producer Responsibility: Companies are responsible for financing the collection, treatment, recycling, and environmentally sound disposal of WEEE. This includes setting up take-back schemes and ensuring proper labeling of products to inform users about disposal options.

Documentation and Labeling

Technical Documentation: Manufacturers maintain detailed technical documentation that demonstrates compliance with RoHS and WEEE directives. This includes material declarations, test reports, and compliance certificates.

Product Labeling: Pump controllers are labeled with appropriate symbols and information to indicate compliance with RoHS and WEEE directives. This helps users and recyclers identify compliant products and handle them appropriately at the end of their life cycle.

By adhering to material restrictions, designing for disassembly, taking on producer responsibility, and maintaining thorough documentation and labeling, pump controllers can ensure compliance with the RoHS and WEEE directives. These measures help reduce the environmental impact of electronic waste and promote the safe use of materials in manufacturing.

How do manufacturers test pump controllers for RoHS compliance?

Manufacturers test pump controllers for RoHS (Restriction of Hazardous Substances) compliance through a series of steps designed to ensure that the products do not contain hazardous materials above the permissible levels. Here are the key steps involved:

Manufacturers begin by selecting materials and components that are known to meet RoHS requirements. This involves sourcing materials that do not contain restricted substances such as lead, mercury, cadmium, hexavalent chromium, and specific brominated flame retardants (PBB and PBDE) beyond the maximum concentration values set by the directive.

Suppliers provide declarations and certifications that their materials comply with RoHS standards. This documentation is crucial for traceability and verification purposes.

One of the primary methods used for RoHS testing is XRF screening. This non-destructive technique uses X-rays to determine the elemental composition of materials. It is a quick and effective way to identify the presence of restricted substances.

For more detailed analysis, samples may be sent to accredited laboratories for further testing. Techniques such as Inductively Coupled Plasma Mass Spectrometry (ICP-MS) or Gas Chromatography-Mass Spectrometry (GC-MS) can be used to precisely measure the concentration of restricted substances.

Once testing is complete, manufacturers obtain compliance certificates from accredited laboratories. These certificates confirm that the pump controllers meet RoHS requirements.

Manufacturers maintain detailed technical documentation that includes material declarations, test reports, and compliance certificates. This documentation is essential for demonstrating compliance during audits and inspections.

Compliant pump controllers are labeled with appropriate symbols and information to indicate RoHS compliance. This labeling helps users and regulatory bodies easily identify products that meet the directive's requirements.

By following these steps — selecting compliant materials, conducting thorough testing, obtaining certifications, and maintaining detailed documentation — manufacturers ensure that their pump controllers comply with RoHS directives. This process helps reduce the environmental impact of hazardous substances and promotes safer manufacturing practices.

What are the specific hazardous substances restricted by the RoHS directive?

The Restriction of Hazardous Substances (RoHS) directive aims to limit the use of specific hazardous materials in electrical and electronic products. Here are the key substances restricted by the RoHS directive:

Lead (Pb)

Usage: Commonly used in solder, glass, and various electronic components.

Hazards: Lead is toxic and can cause neurological damage, particularly in children.

Mercury (Hg)

Usage: Found in switches, relays, and fluorescent lamps.

Hazards: Mercury is highly toxic and can damage the brain, kidneys, and lungs.

Cadmium (Cd)

Usage: Used in batteries, pigments, coatings, and as a stabilizer in plastics.

Hazards: Cadmium is carcinogenic and can cause lung and kidney damage.

Hexavalent Chromium (Cr VI)

Usage: Used in metal coatings to prevent corrosion.

Hazards: Hexavalent chromium is carcinogenic and can cause respiratory problems.

Polybrominated Biphenyls (PBB)

Usage: Used as flame retardants in plastics.

Hazards: PBBs are toxic and can disrupt endocrine function and cause reproductive issues.

Polybrominated Diphenyl Ethers (PBDE)

Usage: Also used as flame retardants in various materials.

Hazards: PBDEs can affect the thyroid and liver and are suspected to be endocrine disruptors.

The RoHS directive restricts the use of these hazardous substances to reduce environmental impact and promote safer manufacturing practices. Compliance with RoHS involves selecting materials that do not contain these substances beyond the permissible levels, conducting rigorous testing, and maintaining proper documentation and labeling.

Pump Controller Media Gallery

Resources

GlobalSpec—Pump Handbook, Third Edition