wtw OxiTop IS 12, Operating Manual

Page: 30 / 44

Measurement Disturbances / System messages
30
ba31107de05 07/2017 ba31107de05 07/2017
31
Recall stored values:
Press S until measured value is displayed (1 second).
Scroll to next day by repressing the S key while the measured
value is displayed (5 sec). Fast scrolling by repeatedly pressing
the S key.

Convert the displayed measured value (digits) into the BOD value with the
following table (Digits x Factor = BOD5 in mg/l):
Sample volume (ml) Measuring range (mg/l) Factor
432 0 - 40 1
365 0 - 80 2
250 0 - 200 5
164 0 - 400 10
97 0 - 800 20
43.5 0 - 2000 50
22.7 0 - 4000 100
Disturbances

Measured value remains below measuring range
The display shows zero or too low a value.
The measuring equipment is not water-tight.
Check rubber quiver, screw top and bottle.
Insufficient sample pretreatment or preservation.
The temperature of the sample had not sufficiently been adjusted (< 15°C).

Measuring range exceeded.
The measuring range chosen is too small. With very high values (> 2000 mg/l) we
recommend to predilute the sample.
Nitrification inhibitor (allylthiourea) is missing or lacking.
Errors due to procedure have not been mentioned.
System messages
Memory empty (
IF
= measured value of day 1 is missing)
Change batteries (approx. every 3 years)
Value remains below measuring range (< 0 digits)
Value exceeds measuring range (> 50 digits)