Campbell Scientific OBS500 Smart Turbidity Meter with ClearSensor Technology - Manual (Page 35)

OBS500 Smart Turbidity Meter with ClearSensor™ Technology
TABLE 7-10. Change in TU value resulting from one hour of
evaporation of SDVB standard, i.e., loss of water but not particles.
Calibration-cup Size φ mm (φ in.) 250 TU 500 TU 2000 TU 4000 TU
100 (4)
+0.26 +0.52 +2.10 +4.20
150 (6) +0.60 +1.20 +4.80 +9.70
Materials and equipment: OBS500 with cable, datalogger, large black
polyethylene plastic tub (0.5 M I.D. X 0.25 M deep) for measuring the clear-
water points, and 100-mm and 200-mm black PE (polyethylene) calibration
cups.
Procedure
1. Swab sensor with an alcohol-soaked towel to sterilize it. Position the OBS
sensor in a large, black tub of fresh tap water as shown in FIGURE 7-6 and
record a 10-second average of the low-range output. Record the average
output on the calibration log sheet.
FIGURE 7-6. Position of OBS500 in clean tap water in big black tub
2. Pour the first SDVB standard into the appropriately sized cup (see TABLE
7-9).
3. Position the OBS sensor in the cup as shown in FIGURE 7-7 and record
10-second averages of the low- and high-range outputs. Record the
average outputs on the calibration log sheet.
4. Pour the standard back into its container.
5. Wipe sensor with a clean, dry towel to remove residual standard.
25