Section 5 – Sensor Calibration
29
5.3 ORP
Calibration
Before attempting an ORP calibration ensure that Temperature has been correctly calibrated (see
section 5.1). A “
∗
” in the Temperature readout in place of the decimal point indicates that
Temperature is NOT calibrated.
5.3.1 ORP
Calibration
Procedure
1. Switch the pool pump OFF with the Pump Timer function (see section 3.6), and unplug it from
the
POOL PUMP
socket.
Remove the pH and ORP/Temperature sensors from their Tee fittings. For installations where
this fitting is below the level of the pool, 6.5mm (1/4”) and 12.5mm (1/2”) bungs can be fitted to
stop the water flow.
2. Press
the button to place the
easyCHEM 770
into Standby mode.
3. Plug the pH sensor into the
pH Probe
socket and the ORP/Temperature sensor into the
ORP
Probe
socket (if not already connected).
4. Remove the wetting cap from the pH sensor. Rinse both sensors in distilled water. Shake off
as much water as possible. Blot the outside of the sensors dry.
5. Make up a fresh sample of ZoBell ORP solution by mixing equal amounts of Part A and Part B.
Approximately 10mL of each one should suffice, depending on the diameter of the calibration
vessel.
6. Place the ORP/Temperature and pH sensors into the made-up ZoBell solution. Ensure that the
entire bulb and reference junction of the pH sensor are immersed. The ORP/Temperature
sensor should be immersed to approximately 20mm above the plastic tip. Refer to the diagram
below.
7. Select ORP Calibration (Press
, select ‘
→
Calibrate
’, then select ‘
→
Cal ORP
’).
The ORP calibration screen is now displayed. For example…
ORP Calibration
230.mV Enter
Press
when the ORP reading on the bottom line becomes totally stable.
