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This economically-priced Standard Platinum Resistance Thermometer, Model 909, is the workhorse of calibration laboratories all over the world. During 2007 we reviewed our range of SPRTs and now have new models in the 909 family, the 909L and 909H. The wide temperature ranges and economic pricing make this thermometer ideal for the secondary laboratory. For smaller uncertainties to suit the Primary Laboratory refer to the Model 670 SPRTs.

The resistance element is of pure platinum, coiled and mounted in a strain free construction. The former is of pure alumina material and all parts have been pre-aged to eliminate contamination and strain. All joints are welded to minimize resistance changes. The leads are brought to a handle assembly where they are connected to a low loss cable, 2M long and screened.

The 909Q has a quartz sheath while the 909L and 909H have metal sheaths. Whilst metal sheathed thermometers appear more robust than the quartz glass models it should be noted that ALL SPRTs are fragile devices and must be handled with care.

Three thermometer lengths are available, standard length 480mm, extra length 550mm or maximum length 600mm.

Quartz glass thermometers have the advantage that the internal components are visible and can be inspected and continue to be our recommended models. The low temperature models have excellent immersion characteristics and a significant cost saving when compared to the higher temperature models.

The Model 909 is supplied with a calibration certificate giving RTPW and Wga. Alternatively we can provide a complete UKAS calibration certificate, see table opposite. For transportation and storage the Model 909 is supplied in its own attractive carrying case.


Technical FeatureValue
RTPW25.5Ω 100Ω
Nominal Resistance25.5Ω at 0°C 100Ω
Recommended max. current mA1 0.5
Nominal Sensitivity0.1Ω/°C 0.4Ω/ °C
Resistance RatioWga>1.11807 as required by ITS-90
Self-heating1mK / 25 microwatts
StabilityDepends upon temperature range of use. Typical annual stability, see the table on the next page.
Internal Leads4 wire-platinum
External LeadsSilver-plated multi-strand wires in a low-loss insulation cable terminating in gold-plated terminals.
How to orderModel 909 specify model, resistance and length. State with UKAS Calibration or without UKAS Calibration. At fixed points or by comparison.


Isotech Model 909 SPRT

-196°C to 670°C

This economically-priced Standard Platinum Resistance Thermometer, Model 909, is the workhorse of calibration laboratories all over the world.

  • Three Stem Lengths
  • Wide Operating Range
  • Proven Design

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