43
SECTION 4,
continued
4.4
Measuring Conductivity
To measure conductivity with the sens
ion
156 meter, press the
CON/TDS/SAL
key until the conductivity icon appears in the lower
left corner of the screen. (The TDS and Sal icons do not appear.)
The instrument will automatically select the appropriate range
and units and will display the conductivity value for the sample
being measured.
For conductivity, place the probe into the sample and make sure
the slot on the end of the probe is totally immersed. Agitate the
sample with the probe for 5–10 seconds to remove bubbles that
may be trapped in the slot.
Table 8 shows the conductivity ranges of common solutions.
4.4.1
Measuring Low Levels of Conductivity
When the non-temperature corrected conductivity is less than
1 µS/cm, the meter automatically uses the temperature correction
coefficients for pure water for the reference temperature selected
(derived from ASTM method D 1125-91, page 253, 1993).
For greatest accuracy, Hach recommends using the Low Ionic
Strength Chamber to prevent gases in the atmosphere from
changing the conductivity level.
1. Make sure the meter is using the non-linear NaCl temperature
correction (see Section 4.2 on page 38).
2. Zero the dry probe by pressing
READ
and
CAL
at the same
time. Insert the conductivity probe into the LIS chamber.
Start the sample flow into the LIS chamber.
Table 8 Conductivity Range of Common Aqueous Solutions
Sample Type
Conductivity Range
High pressure boiler water
<0.1 µS/cm to 0.2 µS/cm
Deionized water
1 µS/cm to 80 µS/cm
Drinking water
100 µS/cm to 1 mS/cm
Wastewater
85 µS/cm to 9 mS/cm
Surface water
100 µS/cm to 10 mS/cm
Industrial process water
8 mS/cm to 130 mS/cm
Concentrated acids and dyes
85 mS/cm to >1000 mS/cm
