User Guide

5
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