22
8. TDS Calibration
Before attempting a TDS calibration ensure that Temperature has been correctly calibrated (see
section 6). A “
∗∗
” in the Temperature readout in place of the decimal point indicates that
Temperature is NOT calibrated.
See section 18 for details on how to select TDS readout mode.
8.1 TDS Calibration Procedure
1. Ensure that the
hydro
CHEM
is in Standby mode (see section 3.3).
2. Plug the Conductivity sensor into the
Cond/Temp
socket.
3. Rinse the sensor in distilled water. Shake off as much water as possible. Blot the outside of the
sensor dry.
Zero Calibration
4. Let the sensor dry in air.
5. Select TDS Calibration (
→
→
F1:Calibrate
→
→
F1:TDS
).
6. The
hydro
CHEM
will recognise the low TDS signal and attempt a Zero calibration. For
example…
0*1ppK 25.0
O
c
Press Enter to Calibrate to Zero
7. When the reading has stabilised at or near zero, press
to calibrate or
to quit. The"
∗
"
will not be removed after a zero calibration.
Standard Calibration
8. Place the Conductivity sensor into a sample of 2.0 ppK standard so that it is immersed at least
to the first vent hole, as per the diagram below.
DO NOT
place the sensor directly into the bottle of standard. Discard the used sample of
standard after use.
9. Select TDS Calibration (
→
→
F1:Calibrate
→
→
F1:TDS
). The calibration screen will
be displayed, with the TDS standard to be used. For example…
2*1ppK 25.0
O
c
Press Enter to Calibrate to 2.0ppK
10. When the reading has stabilised, press
to calibrate. The"
∗
"will now be replaced by a
decimal point if calibration was successful.
11. The
hydro
CHEM
is now calibrated for TDS and is ready for use in this mode.
