User Manual

<4. COMMISSIONING OF pH/ORP>
4-5
IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00
l Matrix
Matrixmeansatemperaturecompensationwhichusesthetemperaturecompensation
matrix.ThetemperaturecompensationmatrixisatableofpHvaluesatvarioustemperatures
correspondingtothepHvaluesatthestandardtemperature.Fordetails,seeAppendix1.
When the temperature or the precompensated pH value is out of the range of the temperature
compensationmatrix,thetemperaturecompensationerror(warning)willbeissued.Thisisnota
device error.
Inthiscase,however,thetemperaturecompensationisperformedbyextrapolation.
NOTE
TodisplaytheprecompensatedpHvalue,settheProcessTemp.Compensationto“None”.
SelectMeasurementsetup→Temp.compensation→ProcessTemp.Compensation.
l NEN6411
This algorithm takes into account the dissociation of water in strong acid and strong alkaline
solutions. It is particularly useful for pH measurement of boiler feed water.
4.2.4 Calibration settings
Thescreenowdiffersdependingonthecombinationofobjectstobemeasured.
Calibration settings for a pH converter involve slope (sensitivity), zero (aspot), and ITP
(isothermalpoint).Figure4.2showsthepHvalueagainstthemVoutputofthesensor.The
characteristicforpHmeasurementisanoffsetalsoknownasaspot[mV]orzero[pH]anda
Slope[%,mV/pH].Foranidealsensor,thetheoreticalslopeis59.16mV/pHat25ºC.Theslope
canbeenteredinmV/pHorasapercentageofthetheoreticalslope(100%correspondsto
59.16mV/pH).ITPrepresentsapHvaluewheretheoutputofthesensordoesnotchangewith
temperature.Notethatslopeandzeroaredenedat25ºC.
ΔpH
ΔmV
ITP (Isothermal point)
Aspot
0 mV
0 °C
10 °C
25 °C
mV
500
0
- 200
14
pH
ITP Zero
0
7
Figure 4.2 Calibration parameters
n
pH settings
l Zero and Slope units
Zero is an alternative to Asymmetry Potential. The method of zero (aspot) unit conforms to the
DINstandardforIEC60746-2instruments.ZeroisdenedinpHormV.
TheunitofSlope(sensitivity)ismV/pHor%(withthetheoreticalvalueas100%).
PH
4