Hanna Instruments HI 96720 User Manual

Page 8

VALIDATION PROCEDURE

• After a few seconds, the display will

show “-0.0-”. The meter is now zeroed
and ready for measurement.

• Remove the blank and insert the second

cuvette into the instrument and ensure
that the notch on the cap is positioned
securely into the groove.

• Press READ/ the lamp, cuvette and

detector icons will appear on the display,
depending on the measurement phase.

• At the end of measurement, the instrument

directly displays concentration in mg/L
(ppm) of calcium hardness, as CaCO

, on

the LCD. To convert the result to mg/L Ca,
multiply the reading by 0.4.

Use the validation procedure to ensure that the instrument is properly calibrated.
Warning:

Do not validate the instrument with any standard solutions other than the HANNA CAL

CHECK

Standards, otherwise erroneous results will be obtained.

• Turn the meter on by pressing ON/OFF.

• Press ZERO/CFM and the lamp, cuvette

and detector icons will appear on the
display, depending on the measurement
phase.

• Place the CAL CHECK

Standard

HI 96720-11

Cuvette A into the cuvette

holder and ensure that the notch on the
cap is positioned securely into the groove.

Now, follow normal measurement procedure. The true value of the sample is the reading
obtained multiplied by a factor of one hundred (the dilution factor).
For your reference, factors to convert readings in mg/L to French degrees (FD), German degrees
(DD) and English degrees (ED) of hardness are as follows:

1 mg/L = 0.1 FD = 0.056 DD = 0.07 ED

INTERFERENCES
Interference may be caused by excessive amounts of heavy metals.

• When the beeper sounds briefly and the

LCD displays dashes, the meter is ready.
The blinking “ZERO” asks for instrument
zeroing.

Note:

the test will detect any calcium or magnesium contamination in the mixing cylinders,

measuring droppers or sample cells. To test cleanliness, repeat the test multiple times
until you obtain consistent results.

SAMPLE DILUTION
This meter is designed to determine low levels of hardness, typically found in water purification
systems.
When testing some other sources of water, it is not uncommon to come across levels of hardness
that are greater than the range of this meter.
This problem can be overcome through dilution. Dilutions must be performed with hardness-free
water or the readings will be erroneus.
• Fill a 1 mL syringe with the sample.
• Place the syringe in a 50 mL beaker, making sure that the beaker is clean and empty, and

inject 0.5 mL into the beaker.

• Fill the beaker up to the 50 mL mark with hardness-free water.