Hanna Instruments HI 93703 User Manual
Page 5
5
IR LED
EMITTED LIGHT (890 nm)
CUVET
LIGHT
DETECTOR
90° SCATTERED
LIGHT
PRINCIPLE OF OPERATION
* 1 FTU = 1 NTU
HI 93703-11 has been designed to perform
measurements according to the ISO 7027 In-
ternational Standard.
The instrument functions by passing a beam of
infrared light through a vial containing the sample
being measured.
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
20
BATTERY REPLACEMENT
All components have been selected to mini-
mize current drain without compromising func-
tionality. In order to minimize the battery con-
sumption, the meter is equipped with an auto-
shut off function which switches the meter off
after 5 minutes of non-use.
The four 1.5V batteries guarantee 60 hours of
working life (or 900 measurements).
In order to obtain accurate measurements, the
battery level is monitored every time the meter
is switched on.
In addition, a "LO BAT" indication will appear on
the lower right corner of the display when the
batteries are weak (<10%). All four batteries
need to be replaced.
When the batteries are too weak to ensure
reliable measurements, the message 0% LO
BAT appears for a few seconds, and then the
meter will automatically switch itself off. Re-
place the batteries immediately.
LOBAT
0
%
LO BAT