FlowMarket
Where to source temperature measurement: FlowMarket is a B2B sourcing network powered by an AI agent. You describe the measurement — sensor type, temperature range, accuracy class, process connection, immersion length, response time, output and approvals — and the AI agent matches you with verified sensor manufacturers and distributors, then requests prices, datasheets and lead times from every match at once. Getting matched is free for buyers.
Sourcing temperature sensors
Temperature is the most measured variable in industry, and also the one most often measured badly. The sensor itself is rarely the problem — the errors come from how it is installed: too short an immersion, a thermowell that damps the response, or a contact measurement on a surface that is not thermally coupled.
That makes temperature a category where describing the application beats quoting a part number. "Pt100" is not a specification; "Pt100, class A, 250 mm immersion, in a thermowell in a 4-inch pipe carrying hot oil at 180 °C, 4–20 mA output" is.
Sensor types
RTDs (Pt100 / Pt1000)
A platinum element whose resistance changes with temperature. The most accurate and stable contact sensor for roughly −200 to +600 °C, and the default for process industry, HVAC and machinery. Class A and class AA define the tolerance; a three- or four-wire connection removes cable resistance error.
Thermocouples
Two dissimilar metals producing a voltage at the junction. Less accurate and less stable than an RTD, but they reach far higher temperatures, respond faster and cost less — the standard for furnaces, kilns, exhaust gas and plastics processing. Type K is the general-purpose choice; J, N, S and R cover specific ranges and atmospheres.
Non-contact and assemblies
- Infrared sensors & cameras — moving, rotating or inaccessible surfaces; emissivity must be set correctly.
- Thermowells — let you replace the sensor without breaking the process; add thermal lag.
- Head transmitters — convert RTD or thermocouple to 4–20 mA, IO-Link or HART at the sensor.
- Bimetal & capillary thermostats — simple mechanical switching without power.
What to specify when sourcing
Include all of this and quotes become comparable — and correct:
- Sensor type — RTD, thermocouple or infrared, or describe the application and let suppliers propose.
- Temperature range — normal operating range plus worst-case excursions.
- Accuracy class — Pt100 class A/AA, or thermocouple tolerance class.
- Process connection — thread, flange, clamp or compression fitting, with size.
- Insertion & stem — immersion length, stem diameter, and whether a thermowell is required.
- Response time — critical for fast control loops; thermowells slow it down noticeably.
- Output — direct resistance/mV, or a head transmitter with 4–20 mA, HART or IO-Link.
- Environment & approvals — vibration, pressure, ATEX, hygienic (EHEDG/3-A), calibration certificate.
Immersion depth: the error nobody quotes for
A temperature sensor reads the temperature of its own tip, and if the stem conducts heat away to a cold flange the reading is low. The usual rule is an immersion of at least ten times the stem diameter into the medium. If your pipe is too small for that, an elbow installation or a smaller-diameter probe fixes it — worth raising in the request, because a supplier who knows the pipe size will quote a sensor that actually measures correctly.