Data Harvest Smart Wireless 1110 Manuel - Page 12

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T = absolute temperature in ˚K (˚C + 273)

F = Faraday constant (96,485.33 C mol

n = valence factor (n = 1 in the case of hydrogen)

At 25˚C the theoretical slope is 2.303 x 8.314 x (25 + 273.15) = 5,708.995 = 59.1695 mV/ per pH unit.

Temperature can affect the pH value in three ways:

1. The pH of the sample can change due to the hydrogen ion activity in the solution being

temperature dependent. This factor is usually ignored because accurate pH measurement will be

desired at that particular temperature.

2. Temperature will affect the glass membranes impedance.

3. Changes in temperature of a solution will vary the millivolt output of the electrode in accordance

with the Nernst equation. Whether or not temperature compensation is needed will depend on

the level of accuracy required.

Trouble shooting

Wild readings, check for air bubbles in the electrode tip.

Response time and stability are affected by the condition of the electrodes glass membrane and

reference solution. Restoration to acceptable levels can often be accomplished by cleaning the

electrode's glass surface.

Sluggish response, erratic readings, or a reading that will not change can indicate electrode demise.

If the sensors are being used in a solution that has a high conductance e.g. seawater take readings

from the sensors individually. (Place one sensor in the solution, take a reading, and remove from the

solution. Place the other sensor in the solution, take a reading and remove).

Investigations



Acid - base titration



Monitoring photosynthesis



Respiration



Fermentation



Activity of enzyme



Studies of household acids & bases



Monitoring pH change during chemical reaction

pH Adaptor & Electrode

-1

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96,485.33