Section 3 Introduction; Measurement Capabilities; Front Panel Features And Controls - Hach Sigma 950 Instrument Manual

Section 3 Introduction

3.1 Measurement Capabilities

The 950 Flow Meter is a portable flow meter that is completely self-contained. With its
rugged construction, the meter is completely sealed—even with the door open.
Conforming to NEMA 4X, 6 standards, the meter also withstands submersion and
corrosive gases—again, with its door open. As a result, access to the meter's keypad is
no problem in manholes, rain, and other harsh weather conditions.
The 950 Flow Meter is suitable for measuring and recording flow in open channels, full
pipes, and surcharged lines. The 950 Flow Meter is most often used to measure flow in
conjunction with a primary measuring device (flume, weir, pipe, etc.) that has a known
level-to-flow relationship. The 950 Flow Meter directly measures the level of liquid in a
channel that is contributing to flow (referred to as "head") and calculates the flow rate
based on the head-to-flow relationship of the primary device.
The flow meter can also measure the average velocity of the flow stream using a
submerged Doppler sensor and calculate flow based on the current level and the
Continuity Equation: Wetted Area × Velocity = Flow.
In addition to its extensive data logging capabilities, the 950 Flow Meter is capable of
enabling a sampler, pacing a sampler, controlling external devices with four Normally
Open/Normally Closed relays, and controlling external devices with two 4–20 mA current
outputs.
Communication capabilities include a standard RS232 port and an optional on-board
modem used for remote data transfer, remote programming, and updating internal
embedded programs using Flash Memory technology (RS232 only). The 950 Flow Meter
also provides SCADA Communication Interface functionality using the Modbus
protocol. This software protocol communicates with the instrument via an RS232
connection.
Using Hach's integrated sewer system management software, users can download,
remotely program, and conduct other data manipulation via RS232 connection or the
optional modem.

3.2 Front Panel Features and Controls

The 950 Flow Meter case has several unique features, all designed to simplify
installation, operation, and maintenance.
The instrument front cover protects the panel controls and display window while providing
a clear view of the flow meter status on the display. The cover also contains two lockable
latches which can be secured with a padlock(s) for security. While a software lock can be
programmed to keep unauthorized personnel from operating the keypad, the front cover
locking ability provides added security against tampering.
The cover perimeter contains a gasket seal to keep moisture and dirt from entering the
front panel area. This seal is not required to maintain the NEMA 4X,6 rating of the case.
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