Hach-Lange SURFACE SCATTER 7 sc Turbidimeter - Manual (Page 13)

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General information
2.2.1.1 Controller
The SS7 sc and SS7 sc-HST operate in conjunction with an sc100
controller. The controller enclosure houses the keypad, display,
microprocessor board and power supply components.
Operating controls and indicators are on the controller. The
controller is used to program the instrument for turbidity level alarm
set points and to perform diagnostic self-tests and
programming operations.
Sample turbidity is displayed continually by the digital display
during normal operation. Because of the automatic decimal point
positioning, no range selection is needed. Indicators of turbidity
level alarm conditions, certain critical system malfunctions or other
possible malfunctions are also on the controller.
Programmable alarm circuits provide three relay closures, both
normally open and normally closed, for selectable turbidity alarm
level set points. Set points can be programmed by the operator
anywhere within the overall range. The alarm circuits can be
programmed for Alarm, Feeder Control, Event Control, PWM
Control, Frequency Control and Warning. Refer to the sc100
manual for setup and use of these different settings. An alarm relay
can be programmed in the sc100 to control the optional Auto
Flush Kit.
The sc100 controller is designed to meet NEMA 4X water-tight
requirements. It is constructed of corrosion-proof materials. It is
suitable for indoor installation. Mounting hardware is included with
the sc100 to provide the capability to wall mount, pipe mount and
panel mount the controller without affecting the environmental
integrity of the case. Electrical access holes are sized for
½-in. conduit.
2.2.1.2 Sample unit
Sample flows through the sample unit ( Figure 4 ) where sample
turbidity is measured. The sample unit enclosure contains all the
electronics for measuring the turbidity. A NEMA 12, corrosion-proof
case protects the optical components and hydraulics from industrial
environments and supplies the measurement signal to the control
unit. The case is designed for wall mounting with external
mounting blocks.
Hydraulic connections to the sample unit are at the bottom of the
enclosure. An air purge fitting is installed in the enclosure bottom.
Air purge is suggested to control condensation inside
the enclosure.