Salinity Indicator Panel

The salinity indicator panel is designed to function

60-Hz power. The cable is secured to the cell by means

in a system having five salinity cells, external alarm

of a gland nut.

bells, and two solenoid trip valves. The panel contains

The electrode assembly comprises the inner

a power unit, a meter unit, five salinity cells, a valve

electrode, adapter, automatic temperature com-

position and meter test unit, and a relay unit, The units

pensator, and the outer electrode. The inner electrode

are of the plug-in type to facilitate removal for

is a hollow platinum-coated brass cylinder closed at

inspection and repairs.

the forward end. It is held in the adapter by means of

POWER UNIT.-- The ship's 115-volt, 60-Hz

a spring-loaded nut on the end of the inner electrode

power is applied to the salinity indicator panel through

holder. A solder lug under this nut connects the white

the power unit (fig. 10-42). The power unit is not a

conductor of the incoming cable.

plug-in type, but is wired directly onto the panel. It is

The outer electrode is a hollow brass cylinder, the

provided with a white power-on indicator lamp, two

inside of which is coated with a thin layer of platinum.

fuse holders, and two blown-fuse indicators. The two

This electrode screws onto the adapter, which in turn

fuses protect only the salinity cell and the alarm circuit

screws onto the cell tube. It is pierced with holes to

wiring. The power circuits to the solenoid-operated

vent the gases trapped in the space between the

control valves are not fused.

electrodes and to allow for free circulation of the

METER UNIT.-- The meter unit (fig. 10-42)

water. The connection for the outer electrode is made

measures the specific electrical conductivity of the

by soldering the green conductor of the incoming

water. The conductivity values are then converted by

cable into the hole provided in the cell tube.

meter scale calibration into equivalent concentrations

The cell body (fig. 10-40, view A) has two

of seawater. The meter is connected to the cell circuits

platinum electrodes with a constant voltage applied to

by individual switches on each salinity cell. The

them. When they are exposed to air, no current flows.

specific electrical conductivity is measured by means

When they are immersed in water, the impurities in

of a bridge circuit that employs a special power-factor

the water determine the amount of current flow. If the

type of meter. The meter measures the ratio of currents

impurities in the water increase, the resistance of the

in the two separate arms of the bridge. One arm of the

water decreases, and this causes a corresponding

bridge is the dilute solution of seawater to be

increase in the current flow. If the current exceeds the

measured. The other arm of the bridge is an automatic

alarm set point, an alarm (visual and/or audible) warns

temperature compensating resistor that has the same

the ship's personnel of the condition.

resistance-temperature characteristics as dilute

solutions of seawater.

A thermistor (fig. 10-40, view B) is located within

the cell which automatically corrects for all

The power-factor type of meter (fig. 10-42)

temperature changes between 40F and 250F. The

employs a fixed coil and a movable coil. The movable

thermistor has a negative temperature coefficient of

coil consists of two windings, A and B, at right angles

resistance, which means that as the temperature

to each other. It is free to rotate within the fixed coil.

increases the resistance decreases. Therefore, the

The movable coil is energized from the secondary of

salinity circuit current is affected only by the

the power transformer, T1. Hence, the currents in

impurities in the water and is unaffected by

windings A and B are in phase with each other and the

temperature changes.

circuits are resistive because of the series limiting

resistor, R6. The fixed coil is energized from the ship's

Salinity Indicator Panel

115-volt, 60-Hz power supply in series with the

voltage dropping resistor, R12. The movable coil turns

The salinity indicator panel (fig. 10-41) indicates

until its resultant field lines up with the field of the

to the operator by meter indication the salinity level

fixed coil. Therefore, the meter indication is directly

of the water at various points in the distillation

dependent on the resultant field of the two movable

process. The salinity indicator panel has switches and

windings, which, in turn, is dependent on the ratio of

alarm indicating lamps for each salinity cell in its

the currents in the two windings. The meter indication

system, as well as an alarm lamp to indicate that the

is independent of minor voltage and frequency

changes of the power supply because there is no iron

dump valve solenoid has "tripped" and water is being

diverted from the potable water tanks. The meter

on the meter magnetic circuits and because the coil

circuits are essentially resistive.

indicating unit is calibrated in epm.

10-27