Sensors, Control & Data
PLC systems, PID controllers, signal isolators and converters, remote I/O, Modbus and industrial Ethernet devices.
This is the system layer above individual instruments: the controllers that execute logic, the I/O that collects field signals, the isolators and converters that let dissimilar systems talk, and the communication devices that carry the data. Where a single panel indicator belongs to Process Instrumentation, a rack of I/O modules belongs here, and the boundary is instrument level against system level.
Selection in this category is dominated by compatibility rather than by performance. The hardware has to fit an existing control platform, an existing network and an existing engineering workflow, and a technically superior device that does not do that is not a candidate. That is why the first question is almost always what is already installed rather than what is required.
The second constraint is lifecycle. Control hardware is installed for a decade or more and is maintained by people who were not present at commissioning, so documentation, spares availability and the programming environment matter as much as the specification sheet. A protocol named on a datasheet is a promise about interoperability, and it is worth confirming what it means for the specific platform rather than assuming.
| Product type | What it does | Usually specified for |
|---|---|---|
| PLC system | Executes deterministic logic and control loops on field inputs and outputs, with its own programming environment | Machine and process control where the sequence, the interlocks and the logic live in one place |
| PID controller | Compares a measurement against a setpoint and drives an output to close a single loop | Standalone loops, panel-mounted control and backup of a loop that the main system also handles |
| Signal isolator | Separates two circuits galvanically so that a ground loop cannot carry interference between them | Protecting an input card and breaking a ground loop between field and control system |
| Signal converter | Translates one signal form into another so that two devices with different interfaces can work together | Fitting a field device to an input that expects a different signal, and re-ranging without changing the sensor |
| Remote I/O | Moves the input and output points close to the field and communicates them back over a network | Distributed plants where long cable runs to a central cabinet are impractical or expensive |
| Industrial communication device | Routes, converts or repeats industrial network traffic between segments | Building the network itself, and joining segments that were installed at different times |
| Modbus device | Exchanges register-based data over serial or TCP links using a widely implemented protocol | Connecting instruments and meters to a controller or a supervisory system where simplicity matters |
| Industrial Ethernet device | Carries deterministic or standard Ethernet traffic on the plant network | Plant networks where several protocols and higher data volumes have to coexist |
Control modules and automation accessories are listed under this category as well.
There is rarely a single correct instrument for a duty, but there is always a shortlist that can be justified and a set of answers that eliminates the rest. These are the questions that decide it.
| Element | Best suited to | Limits | What it decides |
|---|---|---|---|
| Compact PLC | Machine-level control with an I/O count that can be fixed at the outset | Expansion is limited by the platform, so later additions may force replacement rather than extension | Logic, sequencing and interlocks |
| Modular PLC with remote I/O | Plant-level control where I/O is distributed near the field devices | Needs a network design, and the chosen protocol decides what can be distributed and at what distance | Distributed control architecture |
| Standalone PID controller | A single loop, or a loop that has to keep running when the main system does not | Panels space and faceplate conventions, plus limited logic beyond the loop itself | One control loop |
| Signal isolator | Breaking ground loops and protecting an input card from field transients | Adds a conversion step, and the isolation class has to match the installation rather than be assumed | Signal integrity between circuits |
| Signal converter | Making two devices with different interfaces work together | Its own accuracy and drift enter the measurement chain, so it is part of the uncertainty rather than outside it | Compatibility between devices |
| Protocol gateway | Joining two networks that do not share a protocol | The mapping has to be configured and maintained, and diagnostics across the boundary are usually limited | Interoperability between networks |
What is left after the technology is chosen is a list of values that only the installation can supply. These are the ones that change the model, the price or the lead time:
Specifications vary by model and application, so no performance figure is stated on this page. Where a parameter has not been documented for a particular model, the product page says so rather than filling the gap with a plausible number. Send the values above and we will return the ones the selected model actually holds.
Frequently asked
The questions that come up before an order rather than after it. If yours is not here, send it with the requirement and we will answer it in the quotation.
Usually, but compatibility is the governing question rather than the specification. The platform, the protocol and the engineering software have to align, and the spare capacity in the existing system sets how much can be added before something has to be replaced. Tell us what is installed today and what has to be extended, and we will answer against that rather than in the abstract.
It comes down to cable runs and how much the plant is prepared to pull. Remote I/O places the points near the field, which shortens analogue runs and reduces the interference they pick up, but it introduces a network segment that has its own availability requirement. Long cable runs to a central cabinet are simpler in architecture but may not be cost-effective or electrically practical at distance.
Enough that the next change does not force a new rack. Sites commonly allow a modest proportion of spare points, and the useful question is how likely a change is, rather than a fixed rule. Where the process is expected to expand, spare capacity in the rack and in the power supply is usually cheaper than a second remote station later.
That the device implements the protocol, not that it will interoperate with a specific platform without configuration. The details that matter - addressing, supported function codes, data mapping and timing - are where interoperability is won or lost. Saying which controller or system it has to talk to is far more useful than naming a protocol on its own.
That varies by platform and is worth asking explicitly, because control hardware is expected to stay in service for many years. What can be quoted is the current documentation, the spares position and lead times for replacement modules. Where a platform is approaching the end of its availability, it is better to know that before the installation than discover it during the first failure.
The scope here is the hardware and its documentation. Programming, commissioning and integration are normally carried out by the site or by an integrator, and it is worth establishing that division at the enquiry stage. What can be provided is the programming environment, the licence arrangement and the manuals the site team needs to maintain the application themselves.
Available now
PID Controllers
Panel-mount PID temperature controllers in four panel sizes, taking thermocouple, RTD, 4-20 mA or 0-10 V inputs and driving relay, SSR, linear and RS-485 outputs.
AMX-HM · PLC Systems
Programmable logic controllers with an integrated touch screen, in 4.3, 7 and 10 inch formats, combining discrete and analogue I/O, PT100 inputs, high-speed counting and relay outputs in one panel unit.
M2 · Signal Isolators
DIN-rail signal isolators and distributors giving 2000 Vrms isolation between input, output and supply, with 0.1%FS transmission accuracy and 10 ms response.
Send the specification and we will confirm the matching instrument, availability and lead time. Minimum order quantity is 1 pc.
Request for quotation
Send the technical detail and we will confirm availability, lead time and terms. In-stock items ship within 48 hours; customized specifications typically take 2-10 days. Minimum order quantity is 1 pc.