Yokogawa EXA PH202 2-Wire pH/ORP Analyzer - Manual (Page 66)

IM12B07D02-01E
Parameter setting 5-15
5-3-3. Calibration functions
Code 20 *∆t.SEC & These functions are used to determine the stability level demanded by the
*∆PH EXA as acceptance criteria for the automatic calibration. for general purpose
electrode systems with a fast response. Where heavy duty electrodes are
used, or when low temperatures are concerned, these values should be adjusted.
When adjusting these settings, the longer the time interval and the smaller the
pH change, the more stable will be the reading. However, it is important to
bear in mind that the time taken to reach stability is an exponential function,
and too ambitious a setting will cause the instrument to wait for a very long
time before accepting a calibration.
Code 21 *AS.LOW & Limit values for the drift of an electrode system before an error is signalled
*AS.HI when a calibration is done. These default values should be adjusted to suit the
application, this will be especially important with enamel or Antimony probes.
In case in service code 27 the Asymmetry Potential is disabled and the Zero
Point is used, service code 21 is used for entering the limits of the Zero Point.
*ZP.LOW & Limit values for zero point, if enabled in service code 27.
*ZP.HI
Code 22 *SL.LOW & Limit values for acceptable slope (sensitivity) calibrations.
*SL.HI
Code 23 *ITP, *SLOPE Values can be entered directly in this section. These data can be provided by
& *ASP the manufacturer of the probe, or by the users laboratory etc. They are
determined independently of the measuring loop.
Note: it is not necessary to enter this data in most cases as the EXA
automatically does this while performing a calibration. The feature is
used in the case of special electrode systems and where calibration in
the process environment is not possible.
Code 24, *BUF.ID The following buffer calibration tables are programmed into the EXA. They are
25, & 26 the primary buffer standards according to NIST (formerly NBS) and various other
national standards. We strongly recommend the use of these buffer solutions as
they give the best buffer capacity, reliability and accuracy when calibrating.
Table 5-1.
These tables may be adjusted in the case that the user wishes to use other
calibration solutions. The “name” of the buffer can be changed at the *BUF.ID
prompt. The other values can then be adjusted in sequence.
Code 27 *ZERO.P As an alternative to Asymmetry Potential, the Zero point can be used to define
and calibrate the EXA pH unit.
Note that this method conforms to the DIN standard for instruments
No. IEC 60746-2.
pH 4 pH 7 pH 9 pH 4 pH 7 pH 9
0 °C 4.00 6.98 9.46 45 °C 4.05 6.83 9.04
5 °C 4.00 6.95 9.40 50 °C 4.06 6.83 9.01
10 °C 4.00 6.92 9.33 55 °C 4.08 6.83 8.99
15 °C 4.00 6.90 9.28 60 °C 4.09 6.84 8.96
20 °C 4.00 6.88 9.23 65 °C 4.11 6.84 8.94
25 °C 4.01 6.87 9.18 70 °C 4.13 6.85 8.92
30 °C 4.02 6.85 9.14 75 °C 4.15 6.85 8.90
35 °C 4.02 6.84 9.10 80 °C 4.16 6.86 8.89
40 °C 4.04 6.84 9.07