Campbell-scientific OBS500 Smart Turbidity Meter with ClearSensor Tech Manuale Utente Scaricare il pdf (Pagina 34)

OBS500 Smart Turbidity Meter with ClearSensor™ Technology

TABLE 7-9. Calibration Materials and Volumes

Side Scatter 90-Degree Materials

Calibration Cup Diameter

(mm/inches)

8594 - 20TU 100 (~4)

8595 - 40TU 100 (~4)

8596 - 125TU 100 (~4)

8597 - 250TU 100 (~4)

8598 - 500TU 100 (~4)

8599 - 1000TU 100 (~4)

OBS Sensor Material

8600 - 125TU 200 (~7.9)

8601 - 250TU 200 (~7.9)

8602 - 500TU 200 (~7.9)

8603 - 1000TU 100 (~4)

8604 - 2000TU 100 (~4)

8605 - 4000TU 100 (~4)

The GFS item numbers, standard values, and volumes required for the standard

low ranges are given in TABLE 7-9. SDVB standards have a shelf life of two

years provided that they are stored in tightly sealed containers and evaporation

is minimized.

The TU values of the standards will remain the same as long as the ratio of

particle mass (number of particles) to water mass (volume) does not change.

Evaporation causes this ratio to increase, and dust, bacteria growth, and dirty

glassware can also cause it to increase. Therefore, take the following

precautions. 1) Always use clean glassware and calibration containers.

2) Don’t leave standards on the bench in open containers or leave the standard

bottles uncapped. Perform the calibration as quickly as possible and return the

AMCO solutions to their bottles. 3) Clean dirty sensors with a clean, alcohol-

soaked cloth to sterilize them before dipping them into the standards.

4) Transfer entire bottles between containers. To avoid aeration, do not shake

excess fluid off the glassware.

Because of the intrinsic errors in the TU value of formazin used by the SDVB

manufacturer (GFS Chemicals) and the dilution procedures, the uncertainty in

the TU value of an SDVB standard is ± 1% of the value indicated on the

standard bottle. Consequently, the TU value of one liter of standard in an

uncovered 100-mm calibration cup will increase ~1% in 10 hours on a typical

summer day (R.H. = 90% and air temp. = 18°C). For example, the TU value of

a 2000-TU standard in a 100-mm cup will increase by about 2 TU (0.1%) per

hour. TABLE 7-10 gives the increases for some other commonly used

standards.

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Campbell-scientific OBS500 Smart Turbidity Meter with ClearSensor Tech Manuale Utente Pagina 34