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Jerguson TruLevel -- Self Powered Remote Reading Liquid Level Indicator

The Trulevel is a direct connected manometric instrument using the slack diaphragm principle to sense and indicate changes in the liquid level for boiler drums, heaters and steam/condensate applications.

Principle of Operation: The reference head is connected to one side of the slack diaphragm by a line from the datum chamber. The other side of the diaphragm is connected to the bottom of the vessel. When the level changes, the net hydraulic at the diaphragm changes. The force is transmitted by a connecting pin causing a leaf spring reaction by the deflection plate.

A magnet is attached to the end of the deflection plate with the poles of this magnet straddling a magnetic helical armature that is enclosed and supported in a non-magnetic cylindrical well. As the magnet moves in a linear manner, the helix rotates to maintain alignment with magnetic poles.

A counterbalanced pointer, attached to the armature, indicates the level of the Trulevel's vertical scale.

Typical Trulevel Installations

A). To 750 WSP, Trulevel is installed with natural compensation datum column and two isolating valves.  Boiler drums, heaters, and similar equipment falls into this category. See Example

B). Over 750 WSP, Trulevel is installed with the temperature compensated datum column and 3 valve equalizing manifold.  Most boiler, heater, marine and other steam/condensate applications can be handled with Trulevel. See Example

C). For boilers where all drum safety valves are set over 900 WSP the ASME Boiler Code allows the use of one water gage and two remote level indicators with Temperature compensated datum chambers and 3 valve manifolds.   Repeaters can provide additional remote readings. See Example


TRULEVEL System to 750 wsp

  Model Description
  75 5"-40" Range, includes standard datum and 2 shut-off valves
  75E 41"-275" Range, includes standard datum and 2 shut-off valves
  75R TRULEVEL with Repeater System (Transmitter and Receiver)
  75A TRULEVEL with Alarm Unit (2 switch)
  75RA TRULEVEL with Repeater and Alarm Unit
Deduct for no std. datum -
Deduct for no std. valves -
TRULEVEL System 751 to 1750 wsp
  Model Description
  175 5"-40" Range, includes standard datum and 2 shut-off valves
  175E 41"-275" Range, includes standard datum and 2 shut-off valves
  175R TRULEVEL with Repeater System (Transmitter and Receiver)
  175A TRULEVEL with Alarm Unit (2 switch)
  175RA TRULEVEL with Repeater and Alarm Unit

Deduct for no temperature compensated datum - 

Deduct for no Manifold - 

The Trulevel Repeater System
The system is composed of two units: The Transmitter attached to the Trulevel and the Receiver located at a distant monitoring station.

The Transmitter consists of a linear variable differential transformer (LVDT) and the supporting solid state electronics.  The moveable core of the LVDT is attached to the pointer in such a way that a change in the Trulevel's reading causes a change in the transformers magnetic coupling.  This is transduced by electronics into a standard 4-20 mA DC analog signal.  This standard process signal may be monitored by the Receiver or, with the installation of a converter, by a computer.

The Receiver is a switchboard class instrument that duplicates the readout of the Trulevel.  Its standard size allows for easy integration into instrument panels.  Since it is a passive receiver, one or more units may be used to monitor the transmitter's output.

The Trulevel Alarm System

A Solid State Alarm Unit is available to provide switch points for control or indicated functions.  The sensing unit is a photoelectric device consisting of a photoconductive cell excited by a long life subminiature lamp.   A shadow device attached to the Trulevel pointer passes between the lamp and photocell at an alarm point.   The resulting change in the signal of the photocell, when electronically amplified, excites a singlepole, double -throw relay.   This relay provides the contacts which may be wired normally open or normally closed.

Standard alarm units provide two, three, or four adjustable alarm points rated at signal level loads for electrical alarms or annunciator panels.  A separate time delay rated at 10 amps is available to operate pumps or fuel cutouts.

Audible and visual alarms are available to alert personnel when high or low alarm points are activated. Larger Image of Alarm Board

Tru Level Accessories
  Suffix Description
  L 3 Light Alarm (use with Alarm Units)
  H * Horn* (Use with Alarm Unit) 155 VAC
  X Extra Receiver (Add to Repeater System)
  - Extra Switch Points (2 standard) to Model 175
  - To add 3 valve manifold to Model 75
  - Extra Switch Points (2 standard) to Model 300
* Specify AC or DC E=extended range
Standard Features of Jerguson's Remote Level Indicator
Trulevel   To Order Trulevel
Liquid Level Ranges: 5" to 275" H€O Select Model Number From Chart
Scales: Double convex, 8" length, 180€ visibility Specify: Type of service (boiler, tank, etc.)
Illumination: Two long-life 115 VAC lamps Operating Pressure
Mounting: Panel or wall Indicating Range
  Electrical Characteristics
Transmitter Dimension between low vessel connection and normal water level
Power Input: 115 VAC. 15 W  
Output: 4 - 20 mA DC To Order Accessories
Output Load: 1000 ohms maximum Select and add suffix letter
Operating Temperature: 40€ - 160€F R-Repeater
  A-Alarm Unit
Alarm Unit H-Audible Unit
Power Unit: 115 VAC, 15 W L-3 Light Unit
Temperature Range: 40€ - 125€F Specify number of switch points on alarm unit (2 standard).
Low Alarm Adjustment: 0 - 35% full scale Specify electrical characteristics
High Alarm Adjustment: 65 - 100% full scale Specify length of connection cable with repeater (if required).
Contact Rating: 1 amp @ 115 VAC or 2 amps @ 26 VDC Resistive  
Scale Curved: 4€" length  
Adjustment: Zero screw on front  
Operating Temperature: 0€ - 125€F  
Mounting: Panel  
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