McNab Model AP-III Aqua Purometer Recording Monitor
There is an emerging trend by governmental
regulatory agencies in the pollution and health fields to require
continuous monitoring and recording of water purity. This monitoring
requirement often includes indicating, alarming, and controlling functions
as well as recording. Even where not explicitly required, continuous and
automatic monitoring is often more practical and economical than periodic
manual laboratory checks. The Aqua Purometer Ill Recording Monitors were
specially developed to meet this growing requirement.
The Aqua Purometer Ill Recording Monitors
for water conductivity, resistivity and pH are designed to provide all the
regulatory agency required monitoring functions in a unitized standard
production unit. McNab has combined a rugged enclosure, modular
construction, and integrated circuit, solid-state electronics to produce a
compact and reliable instrument. Considerable design effort has been
expended to make the unit easy to install, operate, and maintain even by
non-technical plant personnel. Use of a standardized design with a minimum
of variables gives an unmatched performance/economy ratio as well as an
assurance of on-going support not possible with custom designs.
Regulatory Agency Requirements
The Aqua Purometer Ill Recording Monitors
meet or exceed all existing agency requirements. Neither currently
prohibited materials nor materials likely to be prohibited have been used
at the water stream. When required the cell may be temperature sterilized
without damage. The instrument automatically corrects for broad
temperature variations of the water. Because the recorder is driven
directly by the automatic operator, interpretive errors are eliminated.
The recorder provides the user with a printed, "hard copy"
record of the water purity. The tapes are easy to store and can be
retained for a minimum of 7 years without significant deterioration. Total
system performance for conductivity and resistivity systems can be
externally validated by use of the optional McNab Cell Test Unit.
The integrated recorder-monitor package
makes installation easy. The enclosure may be either wall mounted or flush
mounted with only four bolts. The only electrical connections required are
the AC line cord and either three color-coded cell leads for conductivity
or a keyed plug-in connector for pH. The installer no longer needs to
worry about electronic compatibility among separate components. Mounting
of the cell is equally simple, merely screw it into a standard NPT piping
tee appropriate for the cell size chosen (either 3/4" or 1" NPT).
Set up of the instrument is easily
accomplished by non-technical personnel. The only operator controls are
the external power On/Off switch and the tamperproof, interior
alarm/controller Level Set controls. To enter the minimum acceptable
purity level (i.e. the point on the meter at which the alarm light and
controller relay are activated), the operator merely depresses a
spring-loaded switch and rotates the level control until the desired set
point is displayed on the large 41/2" meter, then releases the
switch. This simple system eliminates errors associated with translating
dial calibrations to meter calibrations, as well as those from loose
pointer knobs and smudged or worn away dial markings. Use of the large
4” meter insures easy readability and higher accuracy in setting of the
alarm and controller threshold than is possible in non-metered systems.
Once the set point is entered, operation is
automatic. The instrument
will simultaneously indicate the water quality on the meter, record it on
the chart recorder, and activate the alarm light and controller relay
should the water quality change to the set point level. Terminals are
provided inside the cabinet for control or remote alarms or solenoid
valves, if desired.
Only minimal maintenance of the systems is
required. The solid-state electronics are extremely reliable. Because of
the modular design, there are only eleven replacement parts in the entire
panel. Conductivity cell deterioration is minimized by the use of noble
metals at the electrode face. PH probe electronics utilize the patented
"Precision Driven Shield" principle. Standard product
configuration requires chart paper replacement every sixty days.
conductivity and resistivity, various threaded cells (3/4” or 1"
NPT) are available, temperature compensated in all ranges. Materials at
cell/fluid interface are extremely corrosion resistant - special materials
of construction also available.
For pH, cell is a combination, gel-filled, one-piece probe with patented "precision driven shield" design.