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Standard Platinum Resistance Thermometers

Standard Platinum Resistance Thermometers or SPRTs are the best temperature probes you can buy. A SPRT probe has to meet stringent criteria. AccuMac are the first company in the world to make  SPRTs using the 'birdcage design'.
Read below about the AM1880. A truly exceptional thermometer.




  • Bird-Cage Design - Improved resistance to mechanical shock
  • Platinum Capsule - High temperature contamination protection
  • Metal Sheath - For harsh environments
  • Temperature Range: From -200 to 670 °C
  • 5.56 mm Diameter - Faster response



AM1880 Standard Platinum Resistance Thermometers (SPRT) interpolate temperature in the range of  -200 °C to 670 °C on the International Temperature Scale of 1990 (ITS-90).  It is designed as a primary or secondary standard thermometer to calibrate other thermometers and to measure temperature precisely in primary and secondary laboratories.

The sensing element and sensor support utilizes a “Bird-Cage” design. The sensor is protected inside a platinum capsule. Compared to the traditional coil wound method, the “Bird-Cage” resists mechanical shock much better and allows for high purity platinum wire to be wound strain-free.  The platinum capsule protects the sensing element from contamination at high temperature. The “Bird-Cage” structure combined with the 5.56 mm Inconel sheath makes this SPRT more responsive to temperature change. All parts used in the SPRT are thoroughly cleaned before assembly and the assembly process is well controlled to protect the sensor from contamination. The gas mixture fill used in the manufacture of each thermometer ensures the sensor wire oxidation effect is as low as possible.

Every AM1880 SPRT is fully tested for stability after manufacture. This world class probe fully meets the ITS-90 criteria for a Standard Thermometer.


Temperature Range -200 °C to 670 °C
Rtpw Nominal 25.5 Ω
Resistance Ratio W(Ga)>=1.11807
Drift at 0.01°C* ΔR(0.01 °C ) <0.006 °C/year, 0.003 °C/year typical
Repeatability < 0.001 °C
Thermal Shock < 0.001 °C after 10 thermal cycles from minimum to maximum temperatures
Self-heating < 0.0015 °C at 1 mA current
Measurement Current 1 mA
Sensor Length 42 mm
Insulation Resistance >1000 MΩ at room temperature
Sheath Material InconelTM
Dimension 5.56 mm (OD) X 500 mm (L)
External Leads Insulated copper wire, 4 leads, 2.5 meters
Termination Gold-plated Spade
Handle Dimension 21mm (OD) X 80 mm (L)
Calibration Not included
Carrying Case Included
*Long-term drift rate is for reference only. It could be affected by handling, application, and maintenance, etc.  


As illustrated in figure 1 below, the AM1880 construction consists of a 500 mm long Inconel sheath, handle assembly and 2.5 meters of external cable. Inside the sheath, a platinum capsule houses the 42 mm sensing element to minimize high temperature contamination. The platinum lead wires connect the sensing element and handle assembly and are insulated by multiple single-bore ceramic tubes and 4-bore ceramic insulation disks. The sheath is hermetically sealed inside the handle assembly.

Figure 1. AM1880 Construction Chart

Inside the platinum capsule a ceramic tube is used to house the sensing element, which is comprised of a high purity platinum wire which is wound strain-free through multiple cylindrical ceramic tubes. See figure 2 below.


Figure 2. AM1880 Sensing Element


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5 / 343 Church Street | Onehunga
Auckland 1061, New Zealand