HF scientific Micro200BW Turbidimeter - 0-100 NTU - Manual (Page 38)

MICRO 200 BW 0-10 & 0-100 NTU (05/05)
Rev. 3.4
the desiccant on a quarterly basis or if after cleaning the
cuvette readings appear erroneously high to ensure
proper operation of the vaporpurge feature. It is impor-
tant to keep a cover on the sample well if the flow
through head is out for more than a few minutes, to
avoid saturating the desiccant uselessly. A replace-
ment desiccant pouch is available from HF scientific or
your local representative HF part# 21555R. See figure
1 on page 6 when replacing the desiccant.
Remember to dry the flow through cuvette of excess
moisture before inserting it into the optical well. This
will speed up the evaporation time.
NOTE: If it should become necessary to return the sen-
sor to the factory, you need only return the upper
sensor assembly and not the base. IF RETURN-
ING THE BASE, THE DESICCANT TRAY
SHOULD BE REMOVED AND STORED IN
A ZIP LOCK BAG BEFORE SHIPPING.
4.3 GRAB SAMPLES
Take extreme care when handling any sample cuvettes.
Surface scratches, dust or finger smudges will cause
analysis error. Examine each cuvette carefully before
the sample is drawn and placed in the Optical Well. We
recommend that the cuvette be wiped clean with a lint-
free laboratory tissue before the sample is drawn. Handle
Reference Standard and cuvettes by the top portion
only.
To take a reading of a grab sample:
1.
Set Averaging to 1 second (see page 19).
2. Remove the flow through unit and insert grab
sample cuvette in Optical Well.
3. The turbidity value of the grab sample will now be
displayed on the readout. Allow at least two updates
(five to ten seconds) for best accuracy before
noting the reading.
NOTE: Settling particles or air in the sample may cause
the digital reading to “hunt”. For best results
take readings before turbid particles settle but
after air bubbles have been allowed to escape.
5.0 ROUTINE MAINTENANCE
5.1 CUVETTE CLEANING & CARE
Cuvettes must be clean and free of marks or scratches
in the critical area (see figure 13 on page 28). Cleaning
is accomplished by washing the interior and exterior of
the cuvette in a detergent solution, then rinsing thor
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discharge side of the flow through unit using the
backpressure valve (Catalog #24008) supplied.
Increasing the size of the incoming line will also help
this condition.
NOTE: Since each application is different, the amount
of back pressure required to eliminate bubbles
must be determined and modified on site during
operation by the customer.
A plastic shut-off clamp is provided on the inlet side of
the flow through unit in order to completely stop flow
to facilitate changing the cuvette. See the section on
cuvette cleaning and care for more information.
The U.S. EPA recommends that cuvettes used for instru-
ment calibration, standardization, or sample measure-
ment be indexed. For quick indexing of the flow through
cuvette, a rotational flow through assembly with lock-
ing collar is supplied.
To index your flow through cuvette, slowly rotate the
flow head through at least one revolution, while observ-
ing the reading, to locate the position of the lowest
reading. Without moving the flow through, press down
on it and turn the locking collar until the flow through
assembly is securely locked in place. See figure 11.
Figure 11
Flow Through Cuvette Indexing
4.2 VAPORPURGE
The MICRO 200 BW is equipped with a continuous
vaporpurge system. A fan inside the sensor continu-
ously circulates heated, dry air around the optical well
and the flow through cuvette. This feature eliminates the
need for connection of a dry purge line. See Figure 12.
The humidity indicator card is blue when dry and turns
to a light pink when the desiccant is expended. Check