Sensortechnik Meinsberg LF 39 Operating Instructions Manual

Edition July 2002

Operating instructions

Meinsberg

Conductivity Meter

LF 39

Sensortechnik Meinsberg GmbH

Fabrikstraße 69, OT Meinsberg Phone : + 49 34327 623-0
D-04720 Ziegra-Knobelsdorf Fax : + 49 34327 623-79

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Please read this information carefully before putting the device into service

Operation and Maintenance Guidelines:

a.) Change of batteries:

If you see the state of charge indication and in the lower display ´bAt´, the battery is nearly discharged.
The instrument is still operable for some time.
The sign ´bAt´ in the upper display shows that the battery is totally discharged. The instrument is not more
operable.

Remove the battery if you do not use the instrument for a longer time!

b.) The instrument and the sensor/electrode has to be used carefully and in accordance with the specifications

in the short-operating instructions. Ensure that all electrical terminations and connections are kept clean
and dry.

c.) To disconnect the temperature sensor do not pull the cable, but use the plug. Ensure to connect plug and

socket in the right direction; you do not need high force for connection.

d.) Operation with Power Supply LF 39-N:
Use the plug mains supply unit N 10 from the manufacturer only.
Before connecting the unit ensure that the mains voltage stated on the delivered plug mains supply unit is

identical with your mains voltage.

Safety Guidelines:

This device has been built and tested according to the safety standards for electronic measuring
instruments. The perfect functioning and operational safety of the instrument can only be ensured if the
user observes the normal safety precautions as well as the specific safety guidelines stated in the
present operating instruction.

1. The perfect functioning and operational safety of the instrument can only be maintained under the climatic
conditions specified in the "Technical data" section of these operating instructions.

2. When th e instrument is moved from cold to warm surroundings, condensate may occur and interfere with
the functioning of the instrument. In such case, the user should wait until the temperature of the instrument
has adapted to the ambient temperature before using the instrument again.

3. Be careful with the connection of other instruments (e.g. via interface).

Wrong connections to external instruments may cause not permissible potentials inside the instrument

(e.g. connections between GND and earth). These potentials may result in malfunctions and damages of
the instrument or the external instruments.

Operation of the instrument with a damaged plug mains supply unit (e.g. short circuit between main

voltage and output voltage) may cause hazards for the user because live parts will become exposed!

4. If there is reason to assume that the instrument can no longer be employed without a risk, it must be set
aside and appropriately marked to prevent further use.
The safety of the user may be endangered, e.g., if the instrument

- shows visible damage,

- no longer operates as specified,

- has been stored over a longer period under unsuitable conditions,

- has been subjected to difficult conditions during transport.

If in doubt, the instrument should as a rule be sent back to the manufacturer for repair and maintenance.

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Contents

1. Application

2. Construction

2.1. Conductivity Cell

2.2. Conductivity Meter

3. Operation

3.1. Putting into operation

3.2. Selection of the measuring parameters

3.3. Selection of the measuring ranges

3.4. Storage of the maximum and minimum values

3.5. Operation mode (configuration menu)

3.6. Measurement

3.7. Maintenance of the conductivity cell

4. Trouble shooting

5. Technical data

6. Delivery volume, accessories and special versions

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1. Application

The model LF 39 is ideal for lab, field and industrial work. The meter features high accuracy,
rugged plastic case, microprocessor-controlled processing and a wide range of application in
conjunction with the conductivity cell with graphite electrodes and built-in temperature probe.
The LCD displays low battery warning. The LF 39 offers different modes for automatic
temperature compensation, selection of the reference temperature and measurements
without temperature compensation. Measurement of the solution resistance, the salinity and
the total dissolved solids (TDS) expand the application range of the LF 39.

2. Construction

2.1. Conductivity Cell

The Conductivity Cell 1/21 has a fixed cable connection to the meter with a length of 1.35 m
and is ideal for general applications in laboratory and field. Two special graphite electrodes
sealed in epoxy feature high mechanical stability, easy purification and low maintenance. A
temperature sensor with low response time is integrated in the cell for automatic temperature
compensation and parallel measurement.

2.2. Conductivity Meter

Display

1 Main display: conductivity (mS, µS), resistance

(kΩ), TDS (total dissolved solids mg/l), salinity
(SAL) resp. user’s instructions

2 Display elements for maximum and minimum
values

3 Display of the dimensions for the measuring
values

4 Warning-signal (low battery warning)
5 Lin/nLF: shows the selected mode for automatic

temperature compensation

6 %/K: Adjustment of the temperature coefficient
7 1/cm: Adjustment of the cell constant

8 Secondary display: measured temperature resp.
user’s instructions