Model 513 - single channel
Model 512 - dual channel
Model 514 - quad channel
Features
The
switch station actuates its relay when a small electrical current flows from
its sensing probe to the vessel wall or to another probe being used for ground
return. A low voltage AC signal is applied between the sensing probe and ground.
The very small current is conducted between the two when the process liquid
touches the sensing probe. This current flow is sensed by an electronics network
which actuates the output relay.
On/off differential control is accomplished by using two sensing probes, one of which is longer than the other. The relay is actuated when the liquid level touches the upper probe. The relay actuation disconnects the upper probe and connects the lower probe to the measuring circuit input. The unit is then "latched in" through the lower probe/liquid/ground connection and remains actuated until the liquid level drops below the lower probe. The relay then deactuates, and the upper probe is reconnected to the measuring circuit input.
A single conductive return path is common to all stations. This path can be a probe, metal tank, earth ground, etc.
This
unit will sense the presence of water and almost any water based compound or
mixture. A solution having 10% or more free water is usually adequate for operation.
Typical examples are: acid, tap water, sodium hydroxide, brines, and mine water.
Most carbons and many carbon bearing solids are conductive and can be detected
by the Models 512/513/514. These solids may be in the form of powders, granules,
or lumps. Typical examples are: coal, coke, graphite, and carbon black.
Calibration and Safety
The relay switches when the conductive material makes an electrical connection between the sensing probe and ground return. The sensing rod(s) length is selected so that the rod tip is at the elevation where switching is required. The instrument only has a low AC voltage on the sensing probe, even under conditions of an open probe circuit. Many competitive devices require hundreds of volts on the probe. This can be extremely dangerous, particularly when used on an open tank or pit application.
The
Delta Controls Model 512 / 513 / 514 does a better job on fluids that leave
conductive deposits than do most other types of level switches. Many process
fluids carry entrained solids, which accumulate on any surface that they contact.
These deposits usually remain conductive after the fluid has dropped off of
the probe and commonly continue to collect until the physical size of the buildup
mass is quite large. The Model 512/513/514 will continue to operate through
a conductive buildup because when the fluid rises and contacts the buildup mass,
the sensing current flow, through the conductive buildup, through the fluid,
and on to ground return. The sensing probe should enter the vessel vertically
from the top. This vertical orientation prevents the collected buildup from
bridging across the rod insulation to the tank wall ground, which could cause
the Models 512 / 513 / 514 to be continuously activated.
Go to Delta Controls Home Page
Go to Sensing Probes used with these level switches
<512>