11
CAL
iB
rA
TiON
6.2. EC / TDS
Preparation
Recommended EC calibration points: 1.41 mS/cm (1413 μS/cm) using
HI70031
EC calibration solution, or 1500 ppm using
HI70442
TDS
calibration solution.
Calibrate the probe frequently for improved accuracy. Additionally, calibration
should be performed:
• Whenever the probe is replaced
• After periodic maintenance
Always use fresh calibration solutions and perform electrode maintenance
prior to calibration (see PROBE MAINTENANCE section).
Procedure
1. Pour calibration solution into clean beakers sufficient to cover the
sensing portion of the probe (4 cm / 1
1/2
”).
If possible, use plastic beakers to minimize any EMC interferences.
For accurate calibration and to minimize cross-contamination, use
two beakers, one for rinsing the probe and one for calibration.
2. Raise and lower the probe in the standard to ensure the entire cell
area is filled with standard.
3. Shake any bubbles off the two electrodes (prongs).
4. Center probe in beaker away from beaker walls.
5. Press the
mS/cm
(or
ppm
) key to select EC or TDS measurement
mode.
6. Rotate the EC/TDS calibration knob until reading is displayed
at 25 °C.
EC/TDS Conversion Factor
HI9813-51
and
HI9813-61
have a variable TDS conversion factor,
automatically adjusted from 0.56 to 0.78 based on actual EC readings
(based on 442 curve for natural water).
