Hanna Instruments HI 254 User Manual

Page 7

If measurements are taken successively in different samples, it is recommended

to rinse the electrode thoroughly with deionized water or tap water and then

with some of the next sample to prevent cross-contamination.

The pH reading is affected by temperature. In order to measure the pH

accurately, the temperature effect must be compensated for. To use the

Automatic Temperature Compensation feature, connect and submerge the

HI 7669/2W temperature probe into the sample as close as possible to the

electrode and wait for a few seconds.

If the temperature of the sample is known, simple manual compensation can

be performed by disconnecting the temperature probe.

The display will then show the default temperature of 25 ºC

or the last temperature reading with theºC tag blinking.

The temperature can now be adjusted with the ARROW keys

(from 9.9 ºC to 120.0 ºC).

mV/ORP MEASUREMENTS
An optional ORP electrode must be used to perform ORP measurements

(see Accessories).

Oxidation-Reduction Potential (REDOX) measurements provide the quantification

of the oxidizing or reducing power of the tested sample.

To correctly perform a REDOX measurement, the surface of

the ORP electrode must be clean and smooth.

Press RANGE to enter mV range.

Submerge the tip of the ORP electrode 4 cm (1½) into

the sample to be tested and allow a few seconds for the

reading to stabilize.

The instrument displays the mV reading on the primary LCD and the

temperature on the secondary LCD.

If the reading is out of range, the closest full-scale value will be displayed

blinking on the primary LCD.