PART THREE - OPERATION
SECTION 5 - CALIBRATING THE ANALYZER
Rev. 2-300
Accu4™ Low-range Turbidimeter System
51
☞
5.2 PRIMARY CAL Method
(requires formazin
suspension)
Preparing
Formazin Solution
Calibration Tip!
If at any time during calibration, the
“CONFIRM FAILURE?” screen appears, press
ENTER
key
to confirm. Then, use
×
×
or
Ø
Ø
key
to select between
“CAL REPEAT?” or “CAL EXIT?” and do one of the fol-
lowing:
•
With the “CAL REPEAT?” screen selected, press
ENTER key
to repeat calibration.
•
With the “CAL EXIT?” screen selected, press
ENTER
key
. After the “CONFIRM ACTIVE?” screen appears,
press
ENTER key
to return the analog outputs and
relays to their active states (MEASURE screen ap-
pears).
This calibration method requires you to first fill the sensor
flow chamber with a primary standard (formazin suspen-
sion) and then enter its known value. Since formazin is the
recommended primary standard, it is used in the instruc-
tions for this method.
Prepare 2000 milliliters of
20 NTU or higher
formazin sus-
pension (USEPA requires 40 NTU to comply with GLI
Method 2) using the following laboratory procedure:
1.
Make the dilution water:
To obtain high-purity, low turbidity water for dilutions,
pass distilled water through a 0.2 micron filter. Rinse
the flask at least twice with filtered water before col-
lecting the dilution water.
2.
Make the stock turbidity suspension:
WARNING:
HYDRAZINE SULFATE IS A KNOWN
CARCINOGEN. TAKE PRECAUTIONS TO AVOID
INHALATION, INGESTION, AND SKIN CONTACT.
A.
SOLUTION 1:
Dissolve 5.00 grams of reagent-
grade hydrazine sulfate, (NH
2
)
2
H
2
SO
4
, in distilled
water and dilute to 500 ml in a volumetric flask.
