37
SECTION 4,
continued
linear conversion. If the correction icon does not appear, the
meter is using the default non-linear NaCl conversion.
Reference Temperature — Conductivity standards typically
have a reference temperature noted on their container. When
measuring solutions that are not at the reference temperature, the
meter automatically adjusts the reading to the conductivity value
that would have been measured if the sample had been at the
reference temperature. The reference temperature choices in the
meter are 20 or 25 °C. The reference temperature default setting
is 25 °C.
Temperature Correction Off and On — Because the activity of
ions in solutions varies with temperature, conductivity
measurements are typically corrected for the sample temperature.
To obtain conductivity measurements that are not temperature
corrected (i.e., using the soil cup), turn this option off. For typical
measurements, ignoring the effects of temperature can result in
significant error. Salinity and TDS always require temperature
compensation, so when those forms of conductivity are being
measured, this setup is ignored. The probe supplied with the
meter measures temperature with a thermistor for automatic
temperature compensation.
When the thermometer and Off icons appear in the Read mode,
the instrument is not correcting the measured conductivity
for temperature.
In Setup mode, when the setting is disabled, the thermometer icon
and
(Off)
are displayed. When this feature is enabled, the
thermometer icon is displayed without the
(Off)
icon.
NaCl or KCl Calibration Standard Selection— The
sens
ion
156 meter allows the user to calibrate using either
sodium chloride (NaCl) or potassium chloride (KCl) standards.
NaCl is the default and is displayed when using sodium chloride
standards. When potassium chloride is selected in setup 11, KCl
is shown on the display. The appropriate temperature correction
coefficients are automatically selected for the standard chosen,
allowing the user to calibrate over a wide temperature range.