Dwyer CLT User Manual

MAINTENANCE/REPAIR

Important Points!

Continuous Level Transmitters

Regular maintenance of the total system is recommended to assure sustained optimum performance. These devices are
not field repairable and should be returned to the factory if recalibration or other service is required. After first obtaining a
Returned Goods Authorization (RGA) number , send the unit freight prepaid to the following. Please include a clear descrip­tion of the problem plus any application information available.

Dwyer Instruments, Inc.
Attn: Repair Department
102 Highway 212
Michigan City , IN 46360

Important Points!

Product must be maintained and installed in strict accordance
with the National Electrical Code and Dwyer product catalog
and instruction bulletin. Failure to observe this warning could
result in serious injuries or damages.

For hazardous area applications involving such things as (but
not limited to) ignitable mixtures, combustible dust and
flammable materials, use an appropriate explosion-proof
enclosure or intrinsically safe interface device.

The pressure and temperature limitations shown on the
individual catalog pages and drawings for the specified flow
switches must not be exceeded. These pressures and
temperatures take into consideration possible system surge
pressures/temperatures and their frequencies.

Selection of materials for compatibility with the media is critical
to the life and operation of Dwyer products. Take care in the
proper selection of materials of construction, particularly wetted
materials.

Life expectancy of switch contacts varies with applications.
Contact Dwyer if life cycle testing is required.

Ambient temperature changes do affect switch set points,
since the specific gravity of a liquid can vary with temperature.

Dwyer Products have been designed to resist shock and
vibration; however, shock and vibration should be minimized.

Filter liquid media containing particulate and/or debris to
ensure the proper operation of our products.

Electrical entries and mounting points in an enclosed tank
may require liquid/vapor sealing.

Dwyer Products must not be field-repaired.
Physical damage sustained by the product may render it

unserviceable.

Series CLT

Designed for continuous liquid level sensing, Dwyer transmitters are considered "components".

Operating Principle

The CLT Series utilizes reed switch/magnet technology. A
magnet-equipped float rises or lowers with corresponding
liquid level. The magnetic field generated from the float
actuates a series of reed switches mounted within a sealed
hollow tube. The series of reed switches is combined with
resistors to form a voltage divider.

When a regulated DC voltage is applied to an CLT, the
resulting voltage output is directly proportional to liquid level.

Installation / Mounting

Units operate normally in any attitude, from vertical to a 30° inclination, up or down.

Meter

(Optional)

Float

Junction

Box

Sealed
Hollow

Tube

DWYER INSTRUMENTS,INC.

P .O.BOX 373 MICHIGAN CITY, INDIANA 46361, U.S.A.

Phone: [phone] www.dwyer-inst.com
Fax: [phone] e-mail: [e-mail]
Lit-By Fax: [phone]

Thread Treatment
Sealing: When threading metal threads into a metal coupling , pipe sealant or Teflon tape is

recommended. Due to potential compatibility problems, when sealing plastic threaded units, a
compatible pipe sealant such as "No More Leaks" from Permatex is recommended.

Tightening (Plastic to Metal): When threading a plastic sensor into a metal coupling, the in­staller should use a suitable wrench and tighten the threads 1 to 1-1/2 additional turns past hand­tight. Over-torquing of the threads will result in damage to the plastic mounting plug.

Tightening (Metal to Metal): When threading a metal sensor into a metal coupling, the installer
should use a suitable wrench and tighten the threads 1-1/2 turns past hand-tight.

Wiring Diagrams

Note: For hazardous area applications, use an appropriate intrinsically safe interface device.

Wiring Diagram

Analog Output (Proportional Voltage)

Red
Black

White

Input: 10 - 30 VDC
Output: Proportional

Voltage

4-20 mA Tank Level Transmitter

Wiring Diagram
(4-20mA Output)

1
3

2

4
5

6

Red
Wht

Blk

Junction

Box

Process

Control

Loop

Transmitter

+VA
Voltage
Source

or

Simulator

R

L

Calibration

The signal conditioner on your CLT has been Factory­set. You do not need to calibrate.

Steps:

Calibration should be performed with the probe

A.

disconnected from the signal conditioner. Turn
off power to loop. Disconnect the red, black and
white wires from terminals 1, 2, and 3.

Adjust both the null and span potentiometers at

B.

approximately mid-range. (Figure 1)
Wire as shown per Figure 2, connecting a jumper

C.

wire in place of the black and white probe wires.
Connect an ammeter in series to monitor loop
current. Apply power to loop. Adjust null pot for
4mA.

Remove power from loop. Reposition the jumper

D.

wire in place of red and white probe wires.
Reapply power and with the span pot, set the
output current to 20mA.

Repeat Steps C and D for final adjustment.

E.

If power is maintained during jumper connections,

F.

current level may increase to 36mA. This is
normal. Current will return to regular readings
when connections are made.

Figure 1

Span

Potentiometer

Null

Potentiometer

Figure 2

Using 300 Ohm Resistor

Red
White
Black

Brown

Wht/Blk

Orange

1

3
2

5

6
4

R

Loop

Customer Wiring

(See Wiring Diagram)

1/2" Trade Size

Ground Terminal

(both Ports)

Place Jumper
Here for 20 mA
Output

Place Jumper
Here for 4 mA
Output

+V (Typically 24V)

Ammeter

_

+

Excitation Required for Transmitters

Using 4-20 mA Signal Conditioners

The minimum excitation required for operation of
transmitters with 4-20 mA, DC signal converters
(See Chart) can be determined for a given total loop
resistance from the graph shown. (Total loop resis­tance = the sum of the DC termination resistance plus
loop resistance.) For optimum operation, which is a
function of source voltage (+VA) and total loop resis­tance, the source voltage value used should be above
the minimum load line for the related loop resistance.

Minimum Excitation Required For Loop Resistance

40

30
20

10

DC Source Voltage

0

0 200 400 600 800 1000 1200

RL (Ohms) Termination Plus DC Loop Resistance

Area

of Operation

Troubleshooting

Verify proper wiring, power supply, and loop resistance. If
transmitter is not functioning properly, isolate the transmitter
from the system and wire per Figure 3. Meter should read
4mA with float at bottom and 20mA with float on top of
transmitter. If unit is still not operating properly, please
consult Factory for further troubleshooting details.

+24V

Return

Figure 3

4.12

AMMETER

COM

mA

Power Supply

(24 VDC)

+

Choose loop resistance (RL)
to match application

_