|Calibration of DiST 4 or Sharp EC meter.
Changes: Salt (NaCl) tablets are a new material that
will replace the KCl
for making calibration solutions.
One(1) tablet mixed with 8 fl oz of Distilled Water should read 2.31 mS on
newer meters. Older meters should read
23.1 (100ÁS). Be sure that tablets
have totally dissolved
prior to calibration. The international standard for
conductivity readings is in mS or milliSiemens, but the older meters
some new meters) measure in 100ÁS or 100 microSiemens.
the world are milliSiemens per centimeter (mS/cm)
or microSiemens per centimeter (ÁS/cm)?
the units for electrical conductivity (EC). Meters set to read 100ÁS/cm
values 10 times higher than those set to read mS/cm. A mS is
equivalent to 1000 ÁS.
For example: 20-10-20 at 100 ppm will read .67 mS/cm higher than the value
of the water
source and 6.7 ÁS/cm higher. If the water source reads .32 mS/cm,
it will read 3.2 ÁS/cm.
The sensor simply consists of two metal electrodes (covered by the black
cap on the meter
to the left) that are exactly 1.0 cm apart and are placed into the
water. A constant voltage
is applied across the electrodes. An electrical current flows through the
water due to this
voltage and is proportional to the concentration of dissolved ions in the
water - the more ions,
the more conductive the water resulting in a higher electrical current
which is measured
electronically. Distilled or deionized water has very few dissolved ions
and so there is almost
no current flow across the gap (low EC). Its not the water that is
dangerous when handling
electrical items around water, but the dissolved ions or solids in the
differ in the amount of salts and therefore how much they will affect the
reading. For example: 20-10-20 has an EC of .66 mS per 100 ppm N
where 21-8-18 has an
EC of .42 per 100 ppm N. Add those numbers to your water source
reading to determine the
right value. Example2: