From Flow Measurement
This property is of importance when considering magnetic flowmeters. In most
designs, the meter is able to detect flow only if the liquid is capable of conducting
electricity to a small extent. Organic liquids such as oils and hydrocarbons are
almost perfect insulators with no significant conductivity. In most cases they cannot
be measured by magnetic meters. The minimum conductivity is always specified
by the manufacturer, and it is very important to be sure the liquid is
sufficiently conductive. A spot check for conductivity sometimes indicates that it
is high enough, but it is quite possible that, at times, the material changes and the
meter can fail to operate.
When conductivity is borderline, be sure to make a number of tests at different times - not just once or twice.

The dimensional units for conductivity are usually given as micromhos/cm,
micromhos/cm3, or siemens (S). Surprisingly, all these mean the same thing; they
refer to the conductance between two plates, one cm2 in area and one centimeter
apart, with the liquid in between them.

Sometimes data is presented as "resistivity" rather than "conductivity." The two
terms are merely reciprocals of each other, and the units of resistivity are...

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© 2001 ISA

Products & Services
Flow Controllers
Flow controllers monitor and maintain flow-rate variables, typically in process applications.
Gas Flow Meters
Gas flow meters are used for measuring the flow or quantity of a moving gas in an enclosed pipe or passage.
Liquid Flow Meters
Liquid flow meters are used to measure the volumetric flow rate or amount of a moving liquid.
Volumetric Gas Flow Switches
Volumetric gas flow switches are devices with a switch output used for measuring the flow or quantity of a moving gas in terms of a unit of volume per unit time, such as cubic feet per minute.
Volumetric Liquid Flow Switches
Volumetric liquid flow switches measure the flow or quantity of a moving fluid in terms of a unit of volume per time, such as liters per minute. These flow sensing devices have a switch output.

Topics of Interest

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