Yokogawa 2-Wire Dual Channel Transmitter/Analyzer FLXA21 Manual de usuario descargar pdf (Pagina 226)

App.2-10

IM 12A01A02-01E 5th Edition : Oct. 31, 2013-00

0 1000 2000 3000 4000 5000

1000

2000

3000

4000

5000

6000

7000

Concentration (mg/L)

Conductivity (µS/cm, 25°C)

MgCI

MgSO

CaCI

NaCI

KCI

Figure 2 Relations of concentration and conductivity

n Calibration solutions for conductivity

The calibration (cell constant) of a sensor does not change unless the sensor is damaged.

It can also appear to change because of coating of the electrodes, or partial blockage.

It does not make sense to regularly recalibrate the FLXA21.

Acalibrationcheck,however,isanothermatter.Whentheobjectiveisclearlydenedasa

diagnosticexercisearegularcheckcanbringanextralevelofsecurityandcondencetothe

measurement.

Sensordamage,and/orcoatingscanbedifculttoseeandthecalibrationcheckcanconrm

their presence, by a deviation from the known solution conductivity. The remedial action should

be to clean the sensor, and carefully check for blockage or damage (not simply to recalibrate).

Higher conductivity solutions should be used where possible. The lower the conductivity of the

testsolution,theeasieritistocontaminate.Carbondioxidefromtheaircanbequicklyabsorbed

to cause an error. All containers must be suitably clean, and all materials suitably pure. Outside of

awell-equippedlaboratorytheseconditionsarehardtomeet.

Also note that the check must be performed with due regard to the cell constant of the sensor,

as it limits the effective working range. The documentation provided with the sensor should be

consultedtodetermineitsmaximumworkingvalue.Byusingacheckingsolutionclosetothe

upper range limit of the sensor, the detection of contamination is better. A slightly contaminated

sensormayreadperfectlyatlowerconductivity,butshowsignicanterrorsathighervalues.This

is caused by the early onset of polarization, the factor that limits the upper range of the sensor

in any case. Polarization is seen in contaminated sensors, and it is for this reason that there is a

sophisticated polarization check built into the FLXA21.

1 2 ... 221 222 223 224 225 226 227 228 229 230 231 ... 245 246

Sin comentarios

Yokogawa 2-Wire Dual Channel Transmitter/Analyzer FLXA21 Manual de usuario Pagina 226