Product family
Automation Components: Process Control Instruments and Indicators
Automation components read process signals, show them to operators and act on them. In a typical loop a sensor measures a variable, an indicator displays it, and a controller compares it with a setpoint and drives a valve, pump or heater.
Application-first selection
Tell us the medium, range and conditions — we match the product type to the duty.
Multi-category sourcing
Instruments, valves, filters, pneumatics and pumps on one enquiry.
Quotation against your specs
Every quote references the parameters you sent, so comparisons are like-for-like.
Engineer-to-engineer support
Ask a technical question before you commit to a model.
How it works
Types and how to choose
A control loop has four parts: a sensor, a transmitter or signal conditioner, a controller and a final control element such as a valve, VFD or heater. The controller subtracts the measured value from the setpoint and adjusts its output to remove the error.
Controllers are described by their action. On/off control switches an output at a threshold and suits slow processes that tolerate cycling, such as a water tank or oven. PID control combines proportional, integral and derivative terms to hold the variable steadily, and is chosen for processes that need stable temperature, pressure or flow. Many panel instruments also offer alarms and retransmission outputs.
Indicators and displays show the value to the operator, often with scaling, alarm relays and a 4–20 mA output. Selection starts with the input: RTD, thermocouple, 4–20 mA, voltage or pulse. Then specify the output: relay, SSR drive or analogue. Panel cut-out size, supply voltage and communication interface complete the specification. For the sensing side, see process control instruments, pressure, temperature, level and flow instrumentation.
| Type | Best suited for | Consider when |
|---|---|---|
| Digital indicator | Displaying a process value with alarms | Control action must be performed by the same unit |
| On/off controller | Simple setpoint control of heaters, pumps and tanks | Process needs tight, stable control |
| PID controller | Stable control of temperature, pressure and flow loops | Process is very slow or tolerates cycling |
| Temperature controller | Furnace, oven and heater control with RTD or thermocouple | Process variable is not temperature |
| Process timer / counter | Sequencing and batch counting | Complex logic requires a PLC |
| Signal conditioner / isolator | Converting and isolating signals between devices | Instruments already share compatible signals |
| Flow indicator and totaliser | Reading and totalising flow signals | Only visual flow confirmation is needed |
Selection guide
Parameters to specify
Send these with your enquiry for an accurate, like-for-like quotation.
Typical applications
- Oven, furnace and heater temperature control
- Tank level and pump control loops
- Pressure regulation on boilers and compressors
- Batch counting and timing
- Process display in control panels
- Signal isolation in instrument cabinets
- Flow totalising and dosing control
Industries
- Chemical and process
- Food and beverage
- Plastics and packaging
- Power and boilers
- Textile
- Machine building (OEM)
FAQ
Frequently asked questions
Answers to the questions buyers most often ask before requesting a quotation.
What is the difference between an indicator and a controller?
An indicator only displays a measured value, usually with alarm relays and perhaps a retransmitted output. A controller compares the value with a setpoint and drives an output to correct the difference. Many controllers also display the value, so check whether control or display alone is needed. Pairing an indicator with a separate controller can be useful where the display must stay in a panel door and the control logic elsewhere.
When should I choose PID instead of on/off control?
Choose PID when the process must hold a stable value, for instance temperature in a sensitive reaction or pressure in a regulated line. On/off control causes a swing around the setpoint and suits tanks, ovens or heaters that tolerate cycling. Process speed and tolerance decide. Many PID controllers also offer auto-tune routines that set the terms for you, which shortens commissioning.
How do I match a controller to my sensor?
The controller's input must be configured for your sensor type: RTD or thermocouple type for temperature, or a 4–20 mA or voltage signal from a transmitter. Mismatched inputs give wrong readings. Tell us the sensor, range and wiring and we can confirm a compatible instrument. Scaling the range correctly, for example setting 4 mA and 20 mA to the transmitter's measuring span, is a common commissioning step.
What is a 4–20 mA signal and why is it common?
It is an analogue current signal where 4 mA represents the bottom of the range and 20 mA the top. Current loops resist electrical noise over long cables, and a reading below 4 mA flags a wiring fault. This makes them a standard link between transmitters and controllers. Loop-powered transmitters take their supply from the same two wires, which keeps installation simple.
What information do you need for a quotation?
Please send the input signal type and range, required outputs and alarms, control action, supply voltage, panel cut-out size, communication needs and quantity. For replacements, include the model number of the existing unit. We can also help find a replacement when a discontinued panel instrument must fit an existing cut-out, so please include dimensions or a photograph.
Need an indicator or controller for your loop?
Send the input signal, output, setpoints, supply and panel size, and we will suggest suitable instruments and quote.