Pt100 vs Pt1000: Which RTD Element Should You Specify?

Pt100 and Pt1000 are the same technology at two resistance levels: 100 Ω and 1000 Ω at 0 °C, following the same IEC 60751 temperature curve shape. Because the curve scales, the two look interchangeable on a datasheet — and in a 2-wire installation they behave very differently. The choice is mostly about lead wires, measuring current and what your instrument actually accepts.

The numbers that matter

Lead-wire error: the Pt1000's big advantage

Both elements sit at the end of copper leads, and lead resistance adds directly to the measured resistance. On a Pt100 that addition is expensive — about 2.6 °C of error per ohm. On a Pt1000 the same ohm costs only 0.26 °C, because each degree is worth ten times as many ohms. This single fact explains most Pt1000 adoption: in a 2-wire hookup with several metres of cable — inside a machine, an air-handling unit, a refrigeration plant — a Pt1000 often delivers better real-world accuracy than a Pt100, without paying for 3-wire or 4-wire cabling.

The advantage shrinks as wiring improves. With a properly installed 3-wire or 4-wire connection, lead effects are compensated for both elements, and the choice returns to compatibility and habit.

Self-heating and measuring current

An RTD is measured by passing a current through it, and that current heats the element slightly. The heating power scales with resistance: at the same current, a Pt1000 dissipates ten times the power of a Pt100. Instruments therefore measure Pt1000 at lower currents (typically 0.1–0.3 mA). In still air or poorly immersed installations, an over-energetic Pt1000 measurement can read measurably high; in liquid or well-immersed duty the effect is negligible for both. The practical rule: let the instrument be designed or configured for the element you fit, and its current will be appropriate.

The compatibility trap

This is where most field mistakes happen. A Pt1000 is not a drop-in replacement on a Pt100 input: the instrument scales the reading by the element's nominal resistance, so a Pt1000 on a Pt100 channel reads wildly wrong (roughly ten times the resistance interpreted on the 100 Ω curve). Many modern transmitters, controllers and PLC modules let you select Pt100 or Pt1000 in configuration — but "many" is not "all", and the installed base of process instrumentation is overwhelmingly Pt100. Before specifying Pt1000 for a plant installation, confirm every input on the loop supports it: transmitter, controller, PLC card, data logger.

Where each element wins

Choose Pt100 when:

• The loop is industrial process instrumentation — transmitters, PLC RTD cards, controllers are Pt100 by default.
• You run 3-wire or 4-wire wiring anyway (lead error already compensated).
• You need the widest choice of constructions, classes (AA–C) and spares compatibility with existing plant standards.

Choose Pt1000 when:

• The design is 2-wire with non-trivial cable length — HVAC, building automation, refrigeration, OEM machinery.
• The device is battery-powered or low-power (lower measuring currents suit Pt1000).
• You are designing a new system end-to-end and can specify matching inputs — many modern HVAC and OEM controllers are Pt1000-native.

Specifying correctly

State the element, class, wiring and the input it will feed: Pt1000, Class B, 2-wire, into a Pt1000-configured controller input is a complete specification. If any part of the loop is legacy Pt100, either stay Pt100 or place a configurable transmitter at the sensor and standardize the long run on 4–20 mA.

Universal Ruike supplies both elements in the same probe constructions — thin-film and wire-wound, Classes AA through C, 2/3/4-wire — and configurable head-mounted transmitters that accept either. If you are converting an installation from one element to the other, tell us what the probes will connect to, and we will flag any input that would silently misread.

Related products:  Platinum Resistance Sensors  ·  Armored Platinum Resistance Thermometer (RTD)  ·  Temperature Transmitter Modules