Hanna Instruments HI 255 User Manual

Page 36

The instrument has two temperature channels: one that measures the tem-

perature from the HI 7662 probe while the instrument is in pH/mV range and

the other that measures temperature from the EC probe while the instrument

is in EC/TDS/NaCl range.

All the instruments are factory calibrated for temperature on both channels.

Hannas temperature probes are interchangeable and no temperature

calibration is needed when they are replaced.

If the temperature measurements are inaccurate, temperature recalibration

should be performed.

For an accurate recalibration, contact your dealer or the nearest Hanna

Customer Service Center, or follow the instructions bellow.

Prepare a vessel containing ice and water and another one containing hot

water (at a temperature of around 50 ºC). Place insulation material

around the vessels to minimize temperature changes.

Use a calibrated thermometer with a resolution of 0.1 ºC as a reference

thermometer. Connect the HI 7662 probe to the appropriate socket for the

pH temperature channel or the HI 76310 probe for the EC temperature

channel.

With the instrument off, press and hold down the CAL&ALT keys, then

power on the instrument to calibrate the pH temperature channel or

CAL and keys and then power on the instrument to calibrate the

EC temperature channel. The CAL tag will appear and the secondary

LCD will show 0.0 ºC.

Immerse the temperature probe (or EC probe) in the vessel with ice and

water as near as possible to the calibrated thermometer. Allow a few

seconds for the probe to stabilize.

Use the ARROW keys to set the reading on the secondary LCD to that of

ice and water, measured by the calibrated thermometer. When the

reading is stable and close to the selected calibration point, READY tag

will appear and CFM tag will blink.

Press CFM to confirm. The secondary LCD will show 50.0 ºC.

TEMPERATURE CALIBRATION

(for technical personnel only)

CAL

GLP

CFM

CAL