Hanna Instruments HI 255 - Manual (Page 16)

16
EC/TDS CALIBRATION
EC calibration is a one-point procedure. Selectable calibration points are 0.00 µS
for offset and 84.0 µS, 1413 µS, 5.00 mS, 12.88 mS, 80.0 mS, 111.8 mS for
slope.
Rinse the probe with calibration solution or deionized water.
Immerse the probe into the solution. The sleeve holes must be
completely submerged. Tap the probe repeatedly to remove
any air bubbles that may be trapped inside the sleeve.
To enter EC calibration, select the EC range and press CAL.
Note: TDS reading is automatically derived from the EC
reading and no specific calibration for TDS is needed.
Pressing CAL when TDS range is selected has no
effect.
For zero calibration, just leave the dry probe in the air. This calibration is
performed in order to correct the reading around 0.00 µS point. The slope is
evaluated when the calibration is performed in any other point.
The “BUF” and “CAL” tags are displayed. The primary LCD will display the EC
reading. The secondary LCD will display the buffer value. The “ ” and “~”
tags will blink.
Select the desired value with the ARROW keys, if necessary.
When the reading is stable, “READY” tag is displayed and “CFM” tag starts
blinking on the LCD, asking for confirmation.
Press CFM to confirm calibration.
The instrument stores the calibration value and returns to
measurement mode.
Note:
•
If the uncalibrated reading is too far from the expected value, the
“WRONG” and “ ” tags will blink. Calibration can not be confirmed.
In this case check if the correct buffer has been used or clean the probe
by following the Cleaning Procedure (see page 45).
S BUF
CAL
S BUF
CAL
READY
CFM