Hach EC1000, Инструкция по эксплуатации

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6. Keeping the ORP shorting lead in contact with the platinum disc, wait for a stable
reading and then press the
ENTER
key twice.
7. Press the
pH/mV
key to return the meter to normal operations. Remove the ORP
shorting lead.
2.3.3.2 ORP Electrode Check
To ensure the ORP electrode is functioning correctly, it is necessary to check its potential
in a solution of known redox potential. The nominal potential of the Hach EC1000 ORP
electrode in Light’s and ZoBell’s solution are given in Table 4. Also see Table 5.
The electrode should read within ±10 mV of the nominal value. The potential of the Hach
EC1000 reference electrode is 32 ±5 mV versus SCE (Saturated Calomel Electrode) in
saturated KCl Solution.
2.3.3.3 mV Offset
Once it has been determined that the ORP electrode is functioning properly, a mV offset
can be performed so that the display reads values which are more familiar to the operator.
For example, if it is known that a process must be held at a set point versus SCE, then the
mV zero can be set at 430 mV when the electrode is placed into Light’s Solution. Now the
display will read mV versus SCE.
1. Remove the electrode from the sample cell.
2. Place the electrode in a sample with a known mV potential.
3. Press CAL to call up the main calibration menu. The display shows:
4. Press the
UP ARROW
key. The display shows:
5. Press
ENTER
. The readout is an edit display with a millivolt value such as 0.0 mV.
(The last value displayed is used.)
Table 5 Potential of Zobell’s Solution as a Function of Temperature
(vs. Standard Hydrogen Electrode)
Temperature (°C) EV Temperature (°C) EV
1 0.481 16 0.448
2 0.479 17 0.446
3 0.476 18 0.443
4 0.474 19 0.441
5 0.472 20 0.439
6 0.470 21 0.437
7 0.468 22 0.435
8 0.465 23 0.432
9 0.463 24 0.430
10 0.461 25 0.428
11 0.459 26 0.426
12 0.457 27 0.424
13 0.454 28 0.421
14 0.452 29 0.419
15 0.450 30 0.417