Instrumentation designed
with the ur in mind
INSTRUCTION MANUAL
PRINCO MODEL L2000
POINT LEVEL CONTROLLER
with NULL-KOTE™
PRINCO INSTRUMENTS INC.
1020 INDUSTRIAL BLVD.
SOUTHAMPTON, PA 18966
TEL: 800-221-9237, 215-355-1500
FAX: 215-355-7766
WEB SITE:
E-MAIL:
Rev 1, 12 Nov 01
Table of Contents
Section 1. Description
A. General Description 1-1
B. Functional Description 1-1
C. L840 Series Probe Description 1-3 Section 2. Specifications
A. 1. L2000 Level Controller 2-1
A. 2. L840 Series Probes 2-1 Section 3. Installation
A. Inspection 3-1
B. Grounding 3-1
C. Probe Mounting 3-1
D. Electrical Connections 3-3
E. Installation in Hazardous Areas 3-5 Section 4. Adjustments and Operation
A. Initial Checkout 4-1
B. Calibration 4-1
C. Alarm Action 4-5
D. Delay Operations and Adjustments 4-5
E. Troubleshooting Guide 4-5 Section 5. Equipment Service 5-1 Illustrations
Figure 1-1. Typical Explosion-Proof Installation 1-3 Figure 1-2. Standard L843 Probe, Dimensional
Drawing 1-4 Figure 1-3. Standard L843 Probe, Descriptive Drawing 1-5 Figure 3-1. Standard Installation 3-2 Figure 3-2. Extended Guard Installation 3-3 Figure 3-3. Electrical Connections, 115 Vac and 230 Vac Units 3-4 Figure 3-4. Electrical Connections, 24 Vdc Unit 3-4 Figure 3-5. Ground Continuity Test 3-5 Figure 4-1. L2000 Adjustment and Indicator Locations 4-1 Figure 4-2. Conductive Process Calibration Procedure 4-3 Figure 4-3. Non-Conductive Process Calibration Procedure 4-4
A. General Description
The Princo Model L2000 is a low-cost, adjustable, RF Impedance point level controller. It may be ud, in conjunction with any Princo L840 Series Sensor Probe, to detect the prence or abnce of process material within a storage vesl.
The basic instrument consists of an electronic chassis within a heavy-duty, cast aluminum, weatherproof, explosion-proof housing. The housing has a removable lid which expos the electronic chassis. The chassis is compod of two circular printed circuit boards which are held together by a removable system of mechanical spacers and electrical interconnects. The chassis is easily removed from the instrument housing, allowing convenient replacement, should troubleshooting be required.
The housing, with internal electronic chassis, attaches directly to any one of the Princo L840 Series point level probes. An electrical and mechanical probe connection is made by simply screwing the housing directly onto the probe upper hub NPT fitting. The probe lower hub NPT fitting threads directly into the storage vesl, thus allowing probe entry into the vesl, as well as, mechanically and electrically fixturing the electronic housing and probe to the vesl construction.
The electronic chassis performs the RF impedance measurement, and compares the measurement with a t-point established by the coar and fine nsitivity adjustments on the top of the chassis. The t-point adjustment is established by making adjustments with actual prence and abnce of process material in the storage vesl. When the vesl's condition changes relative to the t-point, two control relays are switched and the Probe Status LED changes state.
B. F unctional Description
The basic function of the device is to detect the prence or abnce of process material within a storage tank or holding vesl, and to announce the process material detection in the form of an “alarmed” t of relay contacts.
The Model L2000, ud in conjunction with an L840 Series Sensor Probe, can detect the prence o
r abnce of a wide variety of process materials, from electrical insulators with low dielectric constants, to highly conductive electrical conductors. The mechanical nature of the materials can range from dry powders or granulars, to liquid materials with virtually any consistency - even thick, viscous materials that verely coat the nsor probe.
1. Basic Features
• RF Impedance Sensing Measurement Technology with Null-Kote TM
The L2000 us RF impedance technology proven in tens of thousands of applications. The principle of operation is very simple: an L840 Series Sensor Probe is mounted in the storage vesl. As the process material changes from not contacting the probe to contacting the probe, a corresponding change in electrical impedance occurs between the probe and the metal storage vesl wall. (For non-metallic storage vesls, a "dual element" probe is ud. In this ca, the impedance change occurs between the "active" and "ground"
elements of the probe.)
The highly nsitive impedance measurement circuits inside the L2000 detect and measure this impedance change by means of a low level, radio frequency current that flows from the
nsor, through the process material and back to the electronics via the metal storage vesl wall (or via the probe ground element). This change in radio frequency current is converted to a proportional DC signal. The electronics compares this DC signal to a t-point determined by the coar and fine nsitivity adjustments, and triggers a change in the state of the Probe Status LED and the Output Control Relay when the signal level travers the t-point level.
• Coating Cancellation
A coating of process material on a probe can effectively simulate a prence condition, even
when the process level is well below the probe. Princo point level probes incorporate a "guard" element which negates this problem. Driven by the electronic circuitry, the guard produces a correction signal, allowing the electronics to respond only to level changes above and below the "active" element of the probe. The unit must be calibrated with the probe coated for the guard to function correctly.
• Heavy Duty Control Relay
Two ts of Form C (DPDT) contacts are provided via a terminal block located on the top printed circuit board of the L2000. The contacts are rated at 10 amps at 115 Vac.
• Probe Status Indicator
The status of the process material at the nsor probe is indicated by the color of the PROBE STATUS LED. The two color (Red/Green) LED is located on the top printed circuit board of the L2000. Green indicates material contacting the probe; Red indicates no contact.
• Coar and Fine Sensitivity Adjustments
Two linearly scaled, single turn potentiometers (SENS, C & F) are provided on the top printed circuit board of the L2000. The adjustments are ud to establish a repeatable switch point that is calibrated to the given application.
• Selectable Alarm Action
A jumper lect switch is provided for programming the alarm action as either high acting, or
low acting. The Alarm Select (FAIL SAFE) is located on the top printed circuit board of the L2000.
A high acting alarm condition occurs when the process material contacts the probe
(prence). A low acting alarm condition occurs when the process material is removed from the probe (abnce). In both cas the alarm condition is defined as a de-energized control relay.
• Fail Safe Alarm Action
The L2000 is in normal, non-alarmed state when its control relay is energized. If the unit were to lo power, the control relay would de-energize. Thus a power failure would produce an alarm condition, alerting the operator that a problem exists.
• Time Delay Adjustment
The L2000 ns the process material level change instantaneously. However, a delay can be inrted between the instant the instrument ns the level change, and the time the control relay correspondingly changes state. A single turn Time Delay (DLY) pot is
provided on the top printed circuit board of the unit. This potentiometer allows an adjustment of 0 to 30 conds of time delay.
The time delay feature is uful when process material wave action caus the control relay to continually change state. It can also be ud to suit a particular control timing application.
Note that the PROBE STATUS LED changes immediately, even when a delay is applied.
Figure 1-1
Typical Explosion-Proof Installation with L2000 Dimensions
C. L840 Series Probe Description
L840 Series Sensor Probes are the probes commonly ud with the L2000. (Refer to Figure 1-2 for
a dimensional drawing of the standard L843 Probe.) The probes have three stainless steel electrical contacts - active, guard and ground - which are parated from each other by Teflon insulators. See Figure 1-3 for location of the contacts on the L843 probes. Electrical contact between the probe elements and the electronic unit is made by simply threading the probe into the electronic housing. The "active" element contacts the L2000 circuit board by means of the spring-loaded pin projecting from the top of the probe. The guard contact is made by means of a ½inch diameter sp r ing which projects from the bottom of the L2000 bottom circuit board. This spring fits concentrically around the spring-loaded pin and touches the guard contact on the probe. The hub of the probe rves as the ground element. It contacts both the electronic housing and the metal storage vesl through its threaded connections with them.
The guard element cancels the effect of any process coating between the ground and active elements, allowing the electronics to respond only to changes in the process material level.
All of the L840 Series Probes have the same three elements, varying only in physical dimensions and configuration as required for various applications.
The L844 Probe (not shown) has a built-in ground reference and is referred to as a "dual element" probe. It is suitable for low viscosity liquids in various low dielectric and non-metallic
