OHAUS STARTER 5000, Руководство по обслуживанию

Страница: 18 / 40

CHAPTER 2 DIAGNOSIS
ST5000 Bench Top pH Meter
Service Manual 2-3 Ohaus Corporation www.ohaus.com
2.4 PROPER CONNECTION of ELECTRODE WITH METER.
 Don‘t bend the cable too much

Check for clean and dry contacts

Use as less adapters as possible
 Don‘t extend the cable

Use correct temperature sensor (NTC30kOhm)
2.5 pH ELECTRODE PREPARARTION BEFORE
CALIBRATION OR MEASUREMENT.
First, unpacking an electrode, then:
1. Remove protecting bottle, (turn off the bottle first, then move the upper cap)
2. Open electrolyte filling hole
3. Check if enough electrolyte is in the electrode, or you need to refill the electrolyte.
4. Check that there are no air bubbles behind the junction

remove through vertical
shaking
5. Rinse electrode with distilled water
6. Never wipe the membrane with a paper towel (electrostatic charge!)

Carefully dab the electrode dry
Then you can calibrate the electrode and start measurement.
Things to consider when calibrate or measure:
1. Electrolyte level must be higher than in the sample solution or buffer.

Otherwise the sample flows into the reference system -> wrong results

Approx. 3 cm higher than sample level
2. Stirring
- often not reproducible
- instable signals because of instable diffusion at the diaphragm
- Non-stirred pH results are often more correct than stirred.
2.6 STORAGE of THE pH ELECTRODES.
1. Rinse the electrode with pure water or distilled water.
2. Recap the electrode with the protection bottle or place the electrode in a beaker with
storage solution.
3.
Close the filling hole.
Always store in:
3 mol/L potassium chloride (3 M KCl, saturated with AgCl)
Never store the electrode in distilled water or dry!
Otherwise the pH sensitive glass membrane will be affected which shortens the lifetime and the
electrode must be reconditioned before use.