ABB AW101, Instruction Manual

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Water Hardness Analyzer
AW101 Testomat 4 Description of Displays and Operating Features
IM/AW101 Rev. C 9
4.8 Analysis Cycle
The analysis cycle comprises the following steps:
a
The flow cell is flushed thoroughly to ensure that an
uncontaminated sample is analysed. This flush time is
programmable to suit the process sample and conditions.
b
The measuring chamber is filled with a known sample
volume.
c
The sample is checked optically to ensure it is clean.
d
A quantity of reagent is titrated and the end-point (color
change) is reached. The result is evaluated and displayed.
If the hardness value is outside the range determined by
the reagent used, an alarm state is triggered and
?
3
4
and
5
are known as the analysis period.
e
The chamber is drained.
f
There is a pause period (programmable) until the next
analysis cycle is started.
4.9 Displayed Unit
Programmed hardness unit is displayed. You have the choice of
°dH, °f, ppm CaCO
3
and mmol/l. The unit entered is displayed
as programmed.
4.9.1 Type of Reagent
Select the reagent type used in the unit – for example, reagent
AW101901 means 0.89 ppm CaCO
3
lower limit of the
measuring range and 8.93 ppm CaCO
3
upper.
4.9.2 Setting the Timer
To ensure the analyzed sample represents the current value, the
sampling tube must be sufficiently well flushed taking its length
into consideration. If the installation has been out of operation
for a long period or in the case of long analysis intervals, a
flushing time in excess of 60 seconds is recommended. A flush
is initiated by simultaneously opening the AW101 inlet and the
outlet valves.
The analysis interval depends directly on the programmed flush
time. If a flush time of, for example, 90 seconds is set, the
analysis interval itself cannot be shorter than 90 seconds.
Example: For 3 bar pressure, a connection longer than 5 m
(16.6 ft), an internal tube diameter of 4 mm (0.16 in), a minimum
internal flushing time of 10 seconds is required to ensure a valid
sample is taken from the sampling tube. The quantity of flush
water for an internal flush of 1 minute is 0.5 liter.
4.9.3 Interval Pause
In the case of timed triggering of the analysis, the interval
between two analyses (plus flush time) is determined by the
interval pause. To carry out analyses continuously, set the pause
to 0. The longest pause is 99 minutes.
4.10 Monitoring the Limit Value
Two limit values are programmable continuously. The range for
the limit value depends on the reagent type used and on the
programmed unit. The functions of these outputs can be
programmed independently from each other.
When limit value LV1 is exceeded, the Status LED LV1 is lit RED
and relay output LV1 reacts as programmed in the switch
function. If the limit value is not exceeded, the display light
remains GREEN. The unit operates in the same way for limit
value LV2.
4.11 Hysteresis
Each limit value output reacts only after the 1
st
, 2
nd
or 3
rd
bad
analysis result has been detected (suppression of the first or the
second measured value).
This increases the reliability during the evaluation of the analysis,
for example, after the measuring point has been switched over
or if the sampling line has possibly not been flushed sufficiently.
The hystereses of the two outputs LV1 and LV2 can be set
independently from each other.
Operation – with a hysteresis of 2 a further analysis is carried out
immediately after the limit value has been exceeded.
The corresponding output is energized only if the limit value of
this analysis is exceeded again. If a hysteresis of 3 is set, the
corresponding output reacts only after the limit value has been
exceeded three times in succession.
Fig. 4.3 Analysis Cycle
Pause
Pause
Analysis
Fill chamber
Fill chamber
Drain chamber
Flush
Drain chamber
1
2
3 4 5
6
7