Theory

Glass thermometers are accurate, economical instruments that measure temperatures of liquid or gas. All of our glass thermometers conform to the International Temperature Scale of 1990 (ITS-90). All Ertco® brand thermometers have individual serial numbers. ASTM thermometers vary from 5.5- to 8-mm diameter; most other thermometers have a 6- to 7-mm diameter. For PTFE-coated or tapered thermometers, call our Application Specialists for ordering information.

Types of Glass Thermometers

Choose your thermometer by the length that will be immersed in the liquid or gas.

  1. Partial Immersion thermometers are immersed in the fluid to the specified immersion depth. The remaining (emergent) portion of the stem is exposed to the air.
  2. Total Immersion thermometers need to be immersed to the liquid temperature mark on the thermometer. If you are unable to immerse properly, see "Definitions—Emergent Stem Corrections" below. Since the thermometer column is fully immersed, these thermometers are the most accurate.

Accuracy

The accuracy of a typical glass thermometer is approximately ±1 scale division. Precision ASTM- and SAMA-designated thermometers are manufactured according to strict performance specifications set by ASTM and SAMA. For accuracy ensured in writing, our ASTM and SAMA thermometers are available with NIST-traceable certificates.

 

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