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Model 670 Standard Platinum Resistance Thermometer. SPRT.
Temperature Range: -200°C to 670°C Model 670 Standard Platinum Resistance Thermometer construction permits the four internal platinum lead wires to expand and contract in the same manner as those of
silver-point thermometers.
The all-quartz construction of the support-members gives the most stable performance with minimal drift,
and a unique platinum radiation shield prevents heat radiating up the inside of the sheath.


Model  Description 
935-14-61 Standard PRT Thermometer Range -200 to +670°C
The construction, including the coiled sensing element, heat-shunt baffles and light scattering barriers,
creates a thermometer of unsurpassed stability.
Because the 670 goes beyond the temperature range of oxide growth to the level at which the oxide
dissociates, the 670 is filled conventionally with argon containing 10% oxygen. A 2-meter length of low
thermal emf, high temperature, screened cable is connected in the handle, via a strain-relieving transition,
to the all pure-platinum construction of the thermometer.
Gold-plated U-shaped terminals complete the cable construction, and the 670 is delivered in an elegant
soft lined carry-case of our own design.
A 670 is delivered only after a stabilizing process which is complete when the reproducibility of
RTPW is within 0.0005°C after excursions to the extremes of its temperature range.
Values of RTPW and WGA are routinely provided with the 670.
The 670 can be supplied with RTPW and WGA only or with full UKAS calibration.
"With calibration" means that you will get an Internationally accepted Fixed Point calibration.
For best accuracy, recommended maximum measuring currents for the 670 is 1mA although up to
10 times this current should not permanently damage the standard.
A comprehensive handbook and tutorial will help you get the very best performance and stability
from your 670. The thermometer has a standard length of 650mm.
Standard PRT
Model 670/25.5
Temperature Range  -200°C to 670°C
Resistance Value (°C)  25.5Ω Ro
Resistance Ratio  WGA>1.11807 as required by ITS-90 
Sensitivity 0.1Ω/°C
Long Term Drift  from 0.001°C/year 
Sheath Length  650mm 
Sheath Diameter  7.5mm 
Calibration  Water T.P., Tin F.P., Zinc F.P., Aluminum F.P.
with print-out of temperature at
W-intervals of 0.01