METER AQUALAB TDL Manuel utilisateur

AQUALAB© TDL

TABLE OF CONTENTS

1. Introduction..............................................................................................1

2. Operation ...................................................................................................2

2.1 Installation ................................................................................................2

2.2 Sample Preparation ...................................................................................3

2.2.1 Sample Composition........................................................................4

2.2.2 Sample Temperature........................................................................5

2.3 Taking a Reading ........................................................................................6

2.4 Viewing Data ..............................................................................................8

2.5 Setting Up Isotherm-Determined Moisture Content ..................................9

2.6 Performing a Linear Offset .......................................................................15

3. System.......................................................................................................18

3.1 Specifications..........................................................................................18

3.2 Components.............................................................................................19

3.2.1 Cords and Cables ...........................................................................20

3.2.2 Sample Chamber............................................................................20

3.2.3 Buttons ..........................................................................................21

3.2.4 Display Screen ...............................................................................22

3.3 Theory......................................................................................................32

3.3.1 Water Activity ................................................................................32

3.3.2 Water Potential ..............................................................................35

3.3.3 Moisture Content ...........................................................................35

3.3.4 Sorption Isotherms ........................................................................35

18286-02

7.19.2021

4. Service.......................................................................................................37

4.1 Verification and Calibration ...................................................................37

4.1.1 Water Activity Verification .............................................................37

4.1.2 Linear Offset ..................................................................................39

4.1.3 Multipoint Calibration....................................................................41

4.1.4 Restore Factory Defaults ...............................................................44

4.2 Cleaning...................................................................................................45

4.2.1 Cleaning Kit....................................................................................46

4.2.2 Cleaning Procedure........................................................................47

4.3 Maintenance Packages ............................................................................48

4.4 Repair ......................................................................................................48

4.5 Troubleshooting .......................................................................................49

4.6 Customer Support....................................................................................51

4.7 Terms and Conditions...............................................................................52

Reference.......................................................................................................53

Index .................................................................................................................54

1. INTRODUCTION

Thank you for choosing the AQUALAB®TDL Water Activity Meter from METER Group, Inc. USA.

AQUALAB is the most accurate and most reliable instrument available for measuring water

activity (aw ).

This manual includes instructions for the AQUALAB TDL and AQUALAB TDL 2. For simplicity,

both will be referred to as "AQUALAB TDL" and all instructions in this manual apply to both

instruments: setting up the instrument, verifying its calibration, preparing samples, and

taking readings as well as instructions on proper care, maintenance, and cleaning. Contact

Customer Support with any questions about your TDL.

Verify all of the listed instrument contents shipped and appear in good condition:

• AQUALAB TDL Water Activity Meter

• Calibration certificate

• Power cord

• USB A to B cable

• 250 disposable sample cups

• AQUALAB Cleaning Kit

• Two vials each of the following verification standards solutions:

1.00 awPure Steam Distilled H2O

0.984 aw0.50 mol/kg KCl

0.920 aw2.33 mol/kg NaCl

0.760 aw6.00 mol/kg NaCl

0.500 aw8.57 mol/kg LiCl

0.250 aw13.41 mol/kg LiCl

OPERATION

2. OPERATION

Please read all instructions before operating the AQUALAB TDL to ensure the instrument

performs to its full potential. Please contact Customer Support at any time for assistance

with installation and setup.

Please observe the following considerations carefully.

• Only allow personnel qualified by METER to carry out service work on the electrical

components.

A Certificate of Calibration will be issued upon completion of the work.

• Never remove the housing of the instrument. There are no parts inside the housing that can

be serviced or replaced by the user.

WARNING: There is a risk of damaging the instrument or of causing serious injury if the live components are touched.

• Only operate this instrument with a main power voltage specified for it (100 to 240 V AC at

50–60 Hz).

• An incorrect main power voltage can damage the instrument.

• Plug the instrument into a grounded outlet or power strip.

• Only use the fuse type and rating specified for this instrument (Section3.1).

If the instrument is used in a manner not specified by the manufacturer, the protection

provided by the equipment may be impaired.

PRECAUTIONS

METER instruments are built to the highest standards, but misuse or neglect may damage

the device and possibly void the manufacturer’s warranty. Before using the AQUALAB TDL,

follow the recommended user instructions and arrange proper protections to safeguard the

instrument from damage.

2.1 INSTALLATION

Follow the steps listed in Table 1 to set up the AQUALAB TDL.

Table 1 Installation

Preparation

Select Clean, Level Location

Preserve cleanliness to prevent contamination of the sample chamber.

Maintain a level surface to reduce the chance of spilling sample material and

contaminating the sample chamber.

Select a location where the temperature remains fairly stable to avoid

temperature changes that can affect accuracy (away from air conditioner and

heater vents, open windows, etc.)

NOTE: Always ensure the sample chamber is empty prior to moving the instrument.

AQUALAB TDL/TDL 2

Table 1 Installation (continued)

Installation

Plug In Instrument

Plug the power cord into the back of the unit and an outlet.

Only use the supplied power cord or one rated for AQUALAB TDL and certiﬁed

for the country of use. The cord must be a minimum of 18 AWG and have a

rating for 10 A or greater.

WARNING: An incorrect main power voltage can damage the instrument.

Turn the Unit ON

Use the power switch on the back of the instrument to turn it on (Section3.2).

Allow the AQUALAB TDL a 15-min warm-up period to ensure the most accurate

readings.

Select the User Proﬁle (Optional)

If user proﬁles are set up, the User screen appears ﬁrst (Section3.2.4).

Use UP and DOWN to select the appropriate user proﬁle.

2.2 SAMPLE PREPARATION

Proper sample preparation is important to keep the AQUALAB TDL clean and achieve

repeatable results. A contaminated sample chamber can lead to unusually long read times

and water activity readings that drift over time.

Carefully prepare and load samples to lengthen time between cleanings and help avoid

downtime. Be consistent in sample preparation methods (e.g., crush, grind, slice the sample)

to obtain reproducible results. For more information on proper sample preparation for

different sample types, visit Six AQUALAB sample preparation best practices (metergroup.

com/food/articles/six-sample-preparation-best-practices).

More specific considerations regarding sample composition and sample temperature are

discussed in Section2.2.1 and Section2.2.2, respectively.

Follow the steps listed below to prepare samples:

1. Make sure the sample to be measured is homogeneous.

Multicomponent samples (e.g., mufﬁns with raisins) or samples that have outside

coatings (like deep-fried, breaded foods) can be measured, but they need to have

representative portions in the cup and may take longer than other sample types

toequilibrate.

2. Place the sample in a disposable sample cup.

a. Completely cover the bottom of the cup, if possible, to provide enough sample to get

an accurate reading.

The AQUALAB TDL is able to accurately measure a sample that does not (or cannot)

cover the bottom of the cup. For example, raisins only need to be placed in the cup

and do not need to be ﬂattened to cover the bottom.

OPERATION

A larger sample surface area increases instrument efﬁciency by providing more

stable infrared sample temperatures. It also speeds up the reading by shortening

the time needed to reach vapor equilibrium.

b. Do not fill the sample cup more than half full.

Overﬁlled cups can contaminate the chamber and do not make the readings faster

or more accurate.

3. Wipe any excess sample material from the rim and outside of the sample cup with a

clean KIMWIPES®tissue prior to loading the sample into the instrument.

Material left on the rim or the outside of the cup can contaminate the chamber and can

be transferred to subsequent samples.

4. If a sample cannot be measured immediately, put the disposable sample cup lid on the

cup to restrict water transfer.

If waiting more than 20 min to measure the sample, seal the cup with Paraﬁlm®wax or a

similar material. Properly sealed samples can be measured up to 4 h aftersampling.

2.2.1 SAMPLE COMPOSITION

The nature of some samples results in longer reading times. These materials may need

additional preparation to ensure accurate readings. Contact Customer Support for questions

on sample composition.

Use the following steps to determine if further sample preparation is necessary:

1. Take several readings of the sample to see if the readings (awand time) stabilize

(Section2.3).

2. If the readings take less than 6 min to stabilize, the sample can be handled normally.

If the readings take longer than 6 min, remove the sample and take a reading of a

veriﬁcation standard (Section4.1.1).

3. If the veriﬁcation standard takes less than 6 min to test, the sample itself is causing the

long read time. Refer to the following sections for pertinent sampling considerations.

If the veriﬁcation standard also takes longer than 6 min to test, the chamber may be

dirty and will need to be cleaned (Section4.2). Retest the sample after cleaning and

verifying the instrument.

2.2.1.1 COATED AND DRIED SAMPLES

Samples with high sugar or fat coatings often require multiple readings because they

equilibrate very slowly with the sample chamber.

Crush or slice the sample before sampling to reduce the time needed to take a water

activity reading for coated or dried samples. This increases the surface area of the sample,

thus decreasing reading times. However, modifying some samples may alter their water

activityreadings.

AQUALAB TDL/TDL 2

For example, a candy may have a soft chocolate center and a hard outer coating. The water

activity reading for the center and the outer coating are different, so one would need to

evaluate which part of the sample needed to be measured before crushing it. When the

candy is crushed, the water activity represents the average water activity of the entire

sample; leaving the candy whole gives a reading for the coating, which may act as a barrier to

the center.

To reduce test time when testing whole samples, see Section3.2.4.2 for Low-Emitting mode.

2.2.1.2 LOW WATEREMITTING SAMPLES

Some extremely dry, dehydrated, highly viscous, water-in-oil emulsions (e.g., butter), high fat,

or glassy compositions may require multiple readings because of their slow water-emitting

properties.The slow emission of water can be interpreted to mean that the head space is in

equilibrium with the sample and cause the instrument to exit the reading prematurely.

The most effective way to test these types of samples is to run them in the AQUALAB TDL

using Continuous or Custom mode and wait for the water activity readings to stabilize.

For faster reading, it is important to have the relative humidity of the chamber at or below

the water activity of these types of samples. This causes the sample to release water to the

vapor phase and equilibrate with the chamber. If the relative humidity of the headspace is

greater than the water activity of the sample, the sample will require a long period of time to

reach equilibrium.

To reduce test time when testing low water-emitting samples, see Section3.2.4.2 to set

Low-Emitting mode.

2.2.2 SAMPLE TEMPERATURE

The ambient temperature of the AQUALAB TDL should be between 4 and 50 °C. The AQUALAB

TDL has temperature control capabilities that enable it to read samples at temperatures

different from ambient temperature but no higher than 50 °C and no lower than 15 °C.

Samples that are more than ±4 °C than the instrument chamber temperature need to

equilibrate to the instrument temperature before taking a reading, ideally within 1 or 2 °C of

the chamber temperature. Rapid changes in temperature over short periods of time cause

the water activity readings to rise or fall until the temperature stabilizes. Proceed with

normal measurements when the temperature stabilizes within an optimal 1 or 2 °C of the

chamber temperature.

High water activity samples that are warmer than the chamber temperature can cause

condensation inside the measuring chamber, which adversely affects subsequent readings.

A warning message appears if the sample temperature is more than 4 °C above chamber

temperature (Figure1).

OPERATION

Figure1 Sample is too hot! message

If this error message appears,

1. Remove the sample from the instrument.

2. Place a lid on the cup.

3. Allow the sample to cool to within 4 °C of the instrument before measuring.

To check the differences in temperature between the sample and the chamber prior to

beginning a reading, set the sample in the chamber, close the lid without latching it, and

press the RIGHT or LEFT button. Figure2 provides an example of this screen.

Figure2 Temperature difference between sample and sample chamber

2.3 TAKING A READING

The AQUALAB TDL provides readings in 5 min or less. Readings are reliable, providing

±0.005 awaccuracy.

CAUTIONS

• Never leave a sample in the AQUALAB TDL after a reading has been taken. The sample may

spill and contaminate the instrument chamber if the instrument is accidentally moved

orjolted.

• Never move the instrument after a sample has been loaded. Movement may cause the

sample material to spill and contaminate the sample chamber.

• Do not measure a sample that differs by more than 4 °C than the AQUALABTDL chamber

(Section2.2.2).

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