Decagon Devices Pawkit Manual de usuario

Portable Water Activity

Measurement System

Operator’s Manual

Ve r. 1 . 3

Decagon Devices, Inc.

950 NE Nelson Court

Pullman , WA 99163

tel: (509) 332-5158

fax: (509) 332-5158

www.decagon.com/pawkit

pawkit@decagon.com

Decagon Devices, Inc.

Pawkit

Table of Contents

Contents

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

About this Manual . . . . . . . . . . . . . . . . . . . . . 1

Customer Service. . . . . . . . . . . . . . . . . . . . . . 1

Warranty. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Note to our Users . . . . . . . . . . . . . . . . . . . . . 2

Seller’s Liability . . . . . . . . . . . . . . . . . . . . . . . 3

2. About the Pawkit . . . . . . . . . . . . . . . . . . 5

How Pawkit works. . . . . . . . . . . . . . . . . . . . . 5

Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Getting Started . . . . . . . . . . . . . . . . . . . . . . . 6

Components of your Pawkit system: . . . . 6

Preparing for Operation . . . . . . . . . . . . . . . 6

3. Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Sample Preparation and Insertion. . . . . . . . 9

Sample Preparation . . . . . . . . . . . . . . . . . . 9

Sample Insertion and

chamber movement . . . . . . . . . . . . . . . . . . 11

Taking Measurements . . . . . . . . . . . . . . . . . 15

Turning it off . . . . . . . . . . . . . . . . . . . . . . . . . 18

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Calibration Standards . . . . . . . . . . . . . . . 19

Steps in Calibration . . . . . . . . . . . . . . . . 20

Sampling Precautions. . . . . . . . . . . . . . . . . .23

Pawkit and Temperature . . . . . . . . . . . . . .24

4. Cleaning and Maintenance . . . . . . . .26

Pawkit

Table of Contents

Cleaning. . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . .27

Disassembly . . . . . . . . . . . . . . . . . . . . . . 27

Sensor Filter Cleaning/Replacement. . . 30

Chamber Cleaning Instructions . . . . . . . . 31

Battery Replacement . . . . . . . . . . . . . . . 32

5. Repair Instructions . . . . . . . . . . . . . . . .36

Shipping Directions . . . . . . . . . . . . . . . . . . .36

Repair Costs . . . . . . . . . . . . . . . . . . . . . . . . .37

6. Theory: Water Activity

in Products . . . . . . . . . . . . . . . . . . . . . . . .38

Water content . . . . . . . . . . . . . . . . . . . . . . . 38

Water activity . . . . . . . . . . . . . . . . . . . . . . .39

Effect of Temperature

on water activity . . . . . . . . . . . . . . . . . . . . . 41

Water Potential . . . . . . . . . . . . . . . . . . . . . .42

Factors in determining

Water Potential . . . . . . . . . . . . . . . . . . . . . .42

Sorption Isotherms—relating aw

to water content . . . . . . . . . . . . . . . . . . . . .44

7. Further Reading . . . . . . . . . . . . . . . . . . .47

Water Activity Theory

and Measurement . . . . . . . . . . . . . . . . . . . .47

Food Quality and Safety . . . . . . . . . . . . . .48

Water Activity and Microbiology . . . . . .49

Water Activity in Foods . . . . . . . . . . . . . . .50

Pharmaceuticals/Cosmetics . . . . . . . . . . . .54

Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . .55

Declaration of Conformity. . . . . . . . . . .57

Pawkit

Introduction

1. Introduction

Welcome to the Pawkit water activity measurement

system. Pawkit allows you to make quick measure-

ments of water activity to ensure the safety of your

product. We hope you find the contents of this man-

ual useful in understanding your instrument and

maximizing its benefit to you.

About this Manual

This manual includes instructions on the operation,

calibration, and maintenance of your Pawkit water

activity system. Please read these instructions care-

fully to ensure that your samples are measured

accurately and that you can fully utilize the instru-

ment’s potential.

Customer Service

If you ever need assistance with your Pawkit, or if

you just have questions, there are several ways to

Phone:

Our toll-free telephone number is available to

those in the US and Canada, Monday through Fri-

Pawkit

Introduction

day, between 8 a.m. and 5 p.m. Pacific time at

1-800-755-2751.

For those outside of the US and Canada, call

(509) 332-2756.

Fax:

Our fax number is (509) 332-5158.When you fax

us, please include your instrument’s serial number,

your name, address, phone and fax number along

with a description of your problem.

E-mail:

If you need technical support, or if you have appli-

cation questions, you can send us messages via

email at pawkit@decagon.com. Again, please

include as part of your message your Pawkit’s serial

number, your name, address, phone, fax number,

and return e-mail address.

Warranty

The Pawkit has a 30-day satisfaction guarantee and

a one-year warranty on parts and labor.

Note to our Users

This manual is written to aid the end user in under-

standing the basic concepts of water activity,

enabling them to use our instrument with confi-

dence. Every effort has been made to ensure that

Pawkit

Introduction

the content of this manual is correct and scientifi-

cally sound.

Seller’s Liability

Seller warrants new equipment of its own manufac-

ture against defective workmanship and materials

for a period of one year from date of receipt of

equipment (the results of ordinary wear and tear,

neglect, misuse, accident and excessive deteriora-

tion due to corrosion from any cause are not to be

considered a defect); but Seller’s liability for defec-

tive parts shall in no event exceed the furnishing of

replacement parts F.O.B. the factory where origi-

nally manufactured. Material and equipment cov-

ered hereby which is not manufactured by Seller

shall be covered only by the warranty of its manu-

facturer. Seller shall not be liable to Buyer for loss,

damage or injuries to persons (including death), or

to property or things of whatsoever kind (including,

but not without limitation, loss of anticipated prof-

its), occasioned by or arising out of the installation,

operation, use, misuse, nonuse, repair, or replace-

ment of said material and equipment, or out of the

use of any method or process for which the same

may be employed. The use of this equipment con-

stitutes Buyer’s acceptance of the terms set forth in

this warranty. There are no understandings, repre-

sentations, or warranties of any kind, express,

implied, statutory or otherwise (including, but with-

Pawkit

Introduction

out limitation, the implied warranties of merchant-

ability and fitness for a particular purpose), not

expressly set forth herein.

Pawkit

About the Pawkit

2. About the Pawkit

The Pawkit is designed to be a simple, rapid and

portable system for measurement of water activity.

It is easy to use, durable, and requires little mainte-

nance.

How Pawkit works

Pawkit uses a dielectric humidity sensor to measure

the awof a sample. In an instrument that uses this

technique, a special porous polymer is placed

between two porous electrodes in the headspace of

a sealed chamber. The electrical properties of the

polymer change depending on the relative humidity

of the chamber. The electrodes give a signal based

upon the relative humidity in the closed chamber.

This signal is then translated by the software and

displayed as water activity on the instrument’s

screen. At equilibrium, the relative humidity of the

air in the chamber is the same as the water activity

of the sample.

Accuracy

The Pawkit is accurate to ±0.02 aw

. For many appli-

cations, this accuracy is more than adequate. If you

Pawkit

About the Pawkit

require higher accuracy in your measurements, we

recommend you use Decagon’s AquaLab water

activity meter, which is a lab-grade, bench-top

instrument that has an accuracy of ±0.003 aw

, and

measures based upon the chilled-mirror dewpoint

method. Contact Decagon for more details.

Getting Started

Components of your Pawkit system:

Your Pawkit should have been shipped to you with

the following items:

• Pawkit main unit

• Durable carrying case

• 110 disposable Sample cups

• 3 spare sensor filters

• 1 cleaning kit

• 1 reusable stainless steel cup

• 2 vials each of the following calibration solu-

tions:

6.0 molal NaCl 0.760 aw

13.41 molal LiCl 0.250 aw

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