Measurement & Process Instrumentation
Thermocouples, RTDs, transmitters, infrared thermometers and controllers for contact and non-contact temperature work.
Temperature is measured either by bringing a sensor into contact with the medium and waiting for it to reach equilibrium, or by reading the infrared energy a surface emits. Contact sensors are cheaper, more accurate and far more common; non-contact sensors exist for targets that no probe can touch, that move, or that would destroy the sensor that touched them.
The sensor element is usually the simplest part of the decision. What determines whether the installation works is the interface: sheath material against a corrosive or abrasive medium, immersion depth against the actual flow, response time against how fast the process changes, and whether a thermowell allows the sensor to be replaced without depressurising the line.
This category covers the element, the assembly around it - protection tube, head, connection - and the electronics that convert a millivolt or resistance signal into something a control room can read.
| Product type | How it works | Usually specified for |
|---|---|---|
| Thermocouple | Millivolt signal generated at the junction of two dissimilar metals | Furnaces, kilns, exhausts and any duty that is hot, fast-changing or where a rugged element matters more than stability |
| RTD and Pt100 | Resistance of a pure metal element changes predictably with temperature | Accurate, stable measurement below roughly 600 C, and any reading that has to be traceable |
| Thermistor | A semiconductor element with a large resistance change over a narrow band | HVAC, medical and appliance duties where sensitivity over a limited range is the priority |
| Temperature transmitter | Conditions an element signal into a linear output | Any duty where the value travels to a control system and cable resistance would otherwise corrupt it |
| Infrared thermometer | Emitted radiance from a surface, converted to a temperature | Moving, rotating, live-electrical or inaccessible targets; food safety checks and predictive maintenance routes |
| Thermal imager | A two-dimensional map of emitted radiance | Fault finding across a panel, a bearing or a building envelope, where the pattern matters more than one reading |
| Thermowell | A pocket that separates the sensor from the process | Pressurised, corrosive or hazardous processes where the sensor must be removable in service |
| Temperature controller | Compares a measured value against a set point and drives an output | Heaters, ovens, baths and packaging equipment where temperature is controlled locally |
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 | Strength | Limitation | Fits best with |
|---|---|---|---|
| Type K thermocouple | Wide range, rugged, low cost, fast response | Drifts with time and at high temperature; needs cold-junction compensation | Furnaces, test rigs, general industrial indication |
| Type J thermocouple | Higher output per degree than type K | Iron leg oxidises; narrower range | Legacy installations and reducing atmospheres |
| Type N and type T | N is more stable than K at temperature; T is preferred at low and cryogenic values | Narrower acceptance in existing plant standards; T has a copper leg that limits its upper range | Specialty duties where drift or low-temperature accuracy dominates |
| Pt100 RTD | Best stability and repeatability below about 600 C; near-linear | Slower than a thermocouple; more expensive; needs three or four wires to cancel lead resistance | Traceable process measurement, custody of quality, laboratory and calibration work |
| Infrared | No contact, so no contamination and no thermal mass; reads a moving target | Emissivity of the target must be known; cannot see through glass or steam; reads a spot, not a bulk | Rotating equipment, live electrical joints, food surfaces, high-temperature stock |
RTD is the more accurate answer; thermocouple is the tougher one. Where both matter, a thermocouple in a thermowell is often paired with an RTD at the same point for verification.
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.
Choose an RTD where the reading has to be stable and traceable and the temperature is below roughly 600 C, which covers most process measurement. Choose a thermocouple where the range is higher, the environment is violent, or the response has to be fast. Where a plant uses both, the usual arrangement is a thermocouple for control and an RTD on the same vessel for verification.
A thermowell is needed when the sensor must be removable without depressurising or draining the process, when the medium would attack the sheath directly, or when the assembly has to contain the line pressure. It adds thermal lag, so the well should be sized for the response the process needs rather than simply chosen as the safest option.
The three usual causes are insufficient immersion, a well that is too heavy for the response time required, and a sensor positioned where it sees the pipe wall rather than the medium. A fourth is a thermocouple that has drifted after long service at temperature. Checking immersion depth and comparing against a second measurement resolves most cases before the instrument is blamed.
Only where a non-contact reading is genuinely acceptable. An infrared instrument reads the radiance from a spot on the surface, so it depends on the emissivity of that surface, and it cannot see through glass, steam or dust. It is the right answer for moving, live or inaccessible targets, and the wrong one where a bulk process temperature is required.
The working range, the medium, the process pressure where a well is involved, the required response time, the immersion length and the connection standard. Also tell us whether the installation has to be traceable, because that decides whether calibration documentation has to accompany the order.
Available now
Thermocouples
Spring-clamp thermocouple with a stainless steel M12×1.5 threaded head and a braided high-temperature shielded lead, for moulds, extruders, heating bands and other points that need a probe pressed into place.
Resistance Temperature Detectors
Stainless steel NTC thermistor probe with a 10 kΩ element at 25°C and a 3950 K B value, supplied with lead wires and plug terminals for control boards and acquisition modules.
Temperature Transmitters
Two-wire temperature transmitter module for RTD and thermocouple inputs, converting the sensor signal to 4-20 mA or 0-10 V from 24 VDC, with 0.2%FS accuracy and zero and span potentiometers.
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.