HF scientific MicroTOL Online Turbidimeter - Manual (Page 15)

MICRO TOL (5/10) 9
Rev. 4.8
4.0 Operation
This process turbidimeter allows for the measurement of the turbidity of process water on-
line. The turbidity of the process water is usually reported in Nephelometric Turbidity
Units (NTU), but may be reported in Formazin Nephelometric Units (FNU). Readings
above 1000 NTU (100 for models 20055 & 20056) are outside the range of this
instrument. Readings above 1100 NTU (110 for models 20055 & 20056) will cause the
display to flash indicating an over range condition.
During normal operation, the instrument will have the arrow beside AUTO highlighted
with the current scale displayed on the lower row of the display and the measured reading
on the upper row of the display (see illustration below).
4.1 Routine Measurement
The following steps describe how to measure the turbidity of a sample using this
instrument:
1. Apply power to the instrument and allow the unit to warm up (typically 45 minutes – 1
hour on initial commissioning).
2. When a continuous process stream is flowing through the instrument, the instrument
will display the measured turbidity level of the sample by displaying it on the LCD
screen. In addition, the equivalent signal is provided on the analog (4-20 mA) output,
or the digital output, depending on the options selected.
4.2 Security Access Feature
The instrument is equipped with a security access code feature that can be activated in the
configuration mode. If the security feature is enabled, the screen shown in the illustration
below will appear when the MODE/EXIT button is pressed.