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7381
User's Guide
Water
Water is often used because of its low cost, availability, and its excellent temperature control
characteristics. Water has low viscosity, good thermal conductivity, and heat capacity which
makes it among the best fluids for stability at lower temperatures. Temperature stability is
reduced at higher temperatures because water condenses on the lid, cools, and drips into the
Bath. Water is safe and relatively inert. The electrical conductivity of water prevents its use in
some applications. Water has a limited temperature range, from a few degrees >0 °C to a few
degrees <100 °C. At higher temperatures, evaporation becomes significant. Use only distilled or
deionized water in the Bath to prevent mineral deposits. To prevent contamination, consider an
algicide chemical added to the water.
Water at temperatures >75 °C (167 °F) may be unstable.
Ethylene Glycol
To prevent personal injury, know that ethylene glycol is extremely toxic.
Extend the temperature range of water with a solution of 1 part water and 1 part ethylene glycol
(antifreeze). The characteristics of the ethylene glycol-water solution are similar to water but with
higher viscosity. Properly dispose of Ethylene glycol.
Mineral Oil
To prevent personal injury, use caution with mineral oil since it is flammable and
can cause serious injury if inhaled or ingested.
Mineral oil or paraffin oil is often used at moderate temperatures above the range of water.
Mineral oil is relatively inexpensive. At lower temperatures, mineral oil is quite viscous and
control may be poor. At higher temperatures, vapor emission becomes significant. The vapors
can be dangerous and Fluke Calibration highly recommends the use of a fume hood or adequate
ventilation. As with most oils, mineral oil expands as temperature increases, see
the Fluid Expansion
than water and temperature stability is not as good. Mineral oil has low electrical conductivity.
Silicone Oil
Silicone oils are available which offer a much wider operating temperature range than mineral oil.
Like most oils, silicone oils have temperature control characteristics which are somewhat poorer
than water. The viscosity changes significantly with temperature and thermal expansion occurs.
These oils have high electrical resistivity. Silicone oils are fairly safe and non-toxic but can be
expensive. Silicone oils can degrade and eventually breakdown when used at higher portions of
their temperature range for long periods. This limits their usable lifetime depending on the
duration spent at high temperature.
18
W
W
Reservoir. The viscosity and thermal characteristics of mineral oil is poorer
Note
Warning
Warning
Rear Panel and
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