5
4
IR LED
EMITTED LIGHT (890 nm)
CUVET
LIGHT
DETECTOR
90° SCATTERED
LIGHT
PRINCIPLE OF OPERATION
* 1 FTU = 1 NTU
HI 93703 has been designed to perform mea-
surements according to the ISO 7027 Interna-
tional Standard.
The instrument functions by passing a beam of
infrared light through a vial containing the sample
being measured.
The light source is a High Emission Infrared
LED with a wavelength peaking at 890 nm,
ensuring that the interference caused by col-
ored samples is minimum.
A sensor, positioned at 90° with respect to the
direction of light, detects the amount of light
scattered by the undissolved particles present
in the sample. The microprocessor converts
such readings into FTU* values.
As noted above, FTU unit is equal to the NTU
unit. However, there are other known measure-
ment units for turbidity: Jackson Turbidity Unit
(JTU) based on the old method of Jackson's
candle, and Silica Unit (mg / L of SiO
2
). For your
reference the conversion table between these
measurement units is shown below:
JTU
FTU/NTU
SiO
2
(mg / L)
JTU
1
19
2.5
FTU /NTU
0.053
1
0.13
SiO
2
(mg / L)
0.4
7.5
1
* 1 FTU = 1 NTU
The meter housing is a rugged and lightweight
case, with an easy-to-read LCD.
To save battery-life, the instrument is equipped
with an automatic shut-off feature which is
activated after 4 minutes of non-use.
The meter is very simple to use: all operations
can be carried out with only four keys and
troubleshooting functions can be performed with
displayed error code guides.
An exclusive positive-locking system guaran-
tees that the cuvet is firmly placed in the cell.
The keypad is water-resistant and can be wiped
with a moist cloth for quick cleanups.
The one-point calibration at 10 FTU* can be
easily performed using the available stan-
dard. In addition, HI 93703 is the first por-
table turbidity meter that allows to store the
last calibration date and to retrieve it at the
user’s convenience.
HANNA instruments has chosen 10 FTU * as
the calibration point because it is the value
that best fits the water turbidity measure-
ments in different applications, from drink-
ing water to wastewater treatment.
HANNA instruments uses the primary standard
AMCO-AEPA-1 to avoid all formazine-related
problems. Formazine is a very toxic, unstable
substance, which requires particular care: its
standards have to be prepared only a few min-
utes before performing the calibration, and can-
not be reused because of their short life. Hanna
Instruments standards are extremely stable,
can be reused, and last up to six months, if free
from contamination.
HI 93703 can be used with both standards.