Omega PHB21 User Manual

PHB21 Portable pH/mV Meter

Instruction Manual

Portable pHmeter

Index

Specifications...............................................................2

PH Measurement.............................................................3

MV Measurement ............................................................7

Parts Description.............................................................8

Equipment Operation.........................................................9

Equipment Operation pH - Set Up...............................................12

Equipment Operation pH - Calibrate ............................................14

Equipment Operation pH - Read ...............................................15

Equipment Operation pH - Check ..............................................16

Equipment Operation pH - Register .............................................17

Equipment Operation mV - Set Up ..............................................19

Equipment Operation mV - Calibrate............................................21

Equipment Operation mV - Read...............................................22

Equipment Operation mV - Check..............................................23

Equipment Operation mV - Register.............................................24

Equipment Operation ºC - Set Up...............................................26

Equipment Operation ºC - Read ...............................................29

Equipment Operation Turning Off...............................................30

Electrode Type pH...........................................................31

Maintenance ..............................................................32

Communication Cables......................................................34

PHB21

Range -2,00 to 20,00 pH Resolution 0.1 / 0.01 pH Relative Precision 0.01 % (full scale)

Range ± 1999 mV Resolution 1 mV Relative Precision 0.05 % (full scale)

Temperature

Range 20 to 120 ºC Resolution 0.1 ºC Relative Precision 0.08% (full scale)

General

Input Impedance 1013 Ù Isopotential Adjust ± 50% Sensibility Adjust 80 to 120 % Temp. Compens. Auto / Manual -20 to 120 ºC Display Alphanumeric 2 lines x 16 characters Datalogging Up to 99 Readings Alarms maximum and minimum Dimensions L x H x D (mm) 100x75x180 Weight 0.45 kg Enclosure IP-67 Power 9Vcc Battery Battery Life 60 hours

Accessories

Glass pH Combined Electrode PHE-21R Buffer Solutions 4.01 pH and 7.00 pH Alkaline Battery 9 V Instruction Manual CD

Optional

Thermocompensator PHE-22R Redox Electrode ORE-22R Depth Probe PHE-221 AC Adapter CDH-30PW (110/220Vac 50/60Hz)

& &

Specifications

pH / ORP / Temperature

Simple 3 keys operation

Automatic Resolution Selection Electrode automatic Check Continuous or Hold Readings Non-Volatile Memory, even when turned off

sustains the set up programmed Automatic Calibration for all parameters Manual or Automatic Temperature

Compensation Maximum and Minimum Sound Alarm Recognizes Buffer Battery Charge Automatic Monitored 99 points Datalogging 110/220Vac Capability (AC Adapter) Supplied with Glass Electrode, Buffers and

Carrying Case

PH Measurement

Stable chemical compounds, are electrically neutral when mixed with water. In order to form a water solution, dismember in positive or negative charged particles. These charged particles are called "i ”. When we apply differential potential in two electrodes immersed in a solution, it is possible to verify that positive ions (H , Na and more) will migrate to the negative terminal, that is why we call them cations. The reverse happens with negative ions (OH , Cl and more) that will migrate to the positive terminal and we call them anions. The ions freedom to migrate thru a solution is measured with the solution ". Chemical compounds that produce conductive solutions are called

lectrolytes Strong

" ". Those that totally dissociate (strong acids, strong bases and salt) are called "

Electrolytes

“Electrical Conductivity

". The others whose dissociation is not big (acids and weak bases) are called " ". For an hypotetical chemical compound "MA" that dissociates in cations and anions , the reaction can be written as:

The arrow indicates that exists a balance between MA not dissociated and the ions M and A dissociated. The extension that this reaction moves to the right or left, varies from one compound to the other and with the solution Temperature. For a specific temperature, there is a relation between the ions activity and the non dissociated molecules, that can vary between 0 up to 100%. This relation is called K Dissociation and it is expressed by the equation:

ons

MA M A

K = aM * aA- / aMA (EQ-1)

++ -

M A

Weak Electrolytes

+and -

“ “

Where: K =

ions activity M+.

For Chloridric acid, the is practically infinity, caused by the complete dissociation for ions and So it is a strong acid:

CTE dissociation.

aM+ =

ions activity A-.

aA- = aMA =

dissociated molecules activity MA.

"K" .

HCl H Cl

+ + -

HCl

On the other hand, Acetic acid has a low . Reacts as the following way:"K"

CH COOH H CH COO

+ + -

Few hydrogen ions result at the solution, so the acetic acid is an weak acid when the most present ion is the OH-, the solution is alkaline.

NaOH Na OH

The sodium hydroxide is totally dissociated, this is the reason for being a On the other hand the Ammonia Hydroxide do not dissociate too much, this the reason for being a .

WEAK BASE(NH OH)

NH OH NH OH

+ + -

STRONG BASE.

+ + -

As we can see, for both acids and bases the strength of a solution depends on the H+ or OH- ion numbers available that depends not only on the compound concentration at the water, but also on the " " Pure water dissociates for Ions H+ and OH-, but it is very weak.

The water molecules number dissociated is low, in comparison with the non dissociated, so we can consider as an activity of HOH equal to 100%.

HOH H OH

+ + -

K dissociation.

PH Measurement (cont.)

At 25°C the of water has a value of 10 where we can take that is the activity product (aH+) by

"K" dissociation (EQ-1)

(aOH-) is equal to ion OH-, the solution is neutral and activities of H+ and OH- must be both of 10 mols / L. If a strong acid, such as HCl, is added to water, many ions H+ are added; this should reduce the number of ions OH-. For example: if added HCl until the OH+ activity turns 10-2 the OH- activity must turn 10-12. The hydrogen potential scale is Established by a definition merely operational, the acid degree or activity of ions H+ will be expressed by therm "pH” (Hydrogenionic potential).

The pH will be defined as:

pH=-log |aH+|

If the activities of ion H+ is 10-x so pH is "x".For example, at pure water @ 25°C, the hydrogen ion activity is 10-7, so the pH Is 7 @ 25°C.An acid solution has more ions H+ then OH-.So the ions H+ activities will be bigger than 10-7, being, 10-6, 10-5 and more. The pHof an acid solution by definition, must be lower than 7, will be 6, 5, 4... If the OH- number exceed the number of ions H+ the H+ activity must be lower than 10-7, being, 10-8, 10-9 and more... The pHwill be bigger then 7, will be 8, 9, 10... To avoid solution ionic concentration modification being measured it is necessary that the current that goes thru the circuitry composed by the galvanic cell (pH electrode) be minimum (I < 1pA), such as the voltage drop caused by the internal resistance of the same electrochemistry cell being null, not to cause measuring errors. Such condition restrict the choice to Choose the instrument to a "HIGH IMPEDANCE VOLTMETER”. The instrument will have a scale graduated in pH, calibrated by glass electrode and a reference electrode based on the relation between the pH and the electromagnetic force Of the cell.

E = E0 - KT (pH)

Above equation, define the equation of a line, whose decline is and whose origin ordenate is . The electrode must

-KT E

have a zero volts point (isopotential), that can be achieve performing a correspondence to 7 to zero volts, to any temperature, using a internal BUFFER at the glass electrode, whose pH variation with the temperature compensates to the temperature variation at the electrode. The approximate decline of the line mV / pH involves the factor adjustment of factor KT @ 59.16 mV decade of pH, @ 25°C by controlling the equipment “ that does the decline around the isopotential. The temperature compensator is

SENSIBILITY"

applied to correct the decline based on real sample temperature, varying the definition of the instrument, relating to a 1pHunit, from54.20 mV @ 0°C up to 66.10 mV @ 60°C.

600 -

500 -

400 -

300 -

200 -

100 -

-100 -

-200 -

-300 -

-400 -

-500 -

-600 -

PH Measurement (cont.)

Electrode Description

pH sensing Bulb

1 - - rugged construction, in order to avoid ease breakage.

Glass Body

2 - - chemically inert.

Punctual Ceramic

3 - .

Seal

4 - - ease operation for electrolyte solution filling.

Low Noise Cable

5 - - assuring stable readings..

Polypropylene Cap

6 - - chemically aggressively resistant.

7 - - avoid contamination with solutions that contain Silver, Mercury, Sulfite, etc.

Ionic Barrier

Avoid AgCl preciptations. Provides quick readings on temperature variations.

8 - - contains reference electrolyte solution for transportation or storage.

Transportation Cap

9 - (on refillable electrodes only).

Electrolyte Fill Hole

10 -

Argental Reference.

Electrode Usage Instruction

DIAPHRAGM

BULB (1)

TRANSPORT CAP (8)

(3)

1 - Before using the electrode, verify it’s body for possible mechanical defects or cracks and in case it occur, replace it immediately. 2 - Take off the transportation cap and rinse the electrode with distilled water, remove eventual crystallization at the diaphragm (3). The transportation cap must always be used when transporting the electrode, avoiding dehydration of the bulb (1). 3 - Remove the seal (4) in order to establish Atmospheric Pressure (only applicable for refillable electrodes) and cl o s e it ag a i n . 4 - Eliminate possible air bubbles that may occur internally at the bulb (1), by shacking the electrode vertically. 5 - On Refillable electrodes, the electrolyte level must be at a maximum of 10 mm below the hole (9). 6 - Always refill, when necessary, the electrolyte level with 3 MKCl thru the hole (9). On Bridge Electrolytic Electrodes, with the proper bridge (see table 1) thru the hole (9). 7 - When the Electrode is not in use, always immerse into electrolyte reference. 8 - To measure, just immerse the electrode into the sample, covering the diaphragm (3). 9 - Switching from one solution to other, always wash electrode with distilled water.

REFILL HOLE

(9)

SEAL

(4)

Buffer Soutions

These are solutions that resist the ph variations, by effect of adding acids or bases and/or by dilution, all happening like if they had an acid reserve and/or alkaline. Selected solutions are used as standard for calibration of ph meters based on operational definition. They are fixed points that define the pH scale. Composed, usually, by a weak acid mixed with its own strong base salt. The KCl is a neutral salt, so does not interfere at the pH value. It can be used to raise the conductivity at the sample, in case we Are measuring a weak electrolyte.

Supplied in 475ml Bottles (other volumes upon request)

OMEGA offers the following Buffer Solutions:

PHA-4 4.01pH PHA-7 7.00pH PHA-10 10.01pH

PH Measurement (cont.)

Oxide Redox Potential Measurement

In order to measure potential redox it is used metallic electrodes, generally Platinum or Silver. This type of electrode refers to chemical reactions in solutions that operate only by electrons transference. Such reactions occur with composed elements presenting two or more oxidizing stages. Ex.: Fe2+ / Fe3+. The redox measurement applications in a determined process, complies with previous knowledge of certain factors: presence of infectants capable of competing with the main redox reaction, approximate values of the ions activity coefficients entering the final equation of the potential differential, approximate speed of the reaction to be controlled, necessary or not to control the pH. At Oxide reduction systems where the ions H+ take part at the reaction, the redox potential depends on the pH. In order to obtain a complete description of such systems it is necessary to indicate, besides the reference electrode, the pH value. The temperature has two effects over the redox potential. First it enters as a factor over the logarithem of equation. This means that a determined reason of the ionic activity, the electrode will develop a different potential. Second, the temperature influence the Ionic activity on each ion of the solution.

MV Measurement

NERNST

Parts Description

Items Description

1 -Display: Alphanumeric 2 Lines x 16 characters 2 -Membrane Keyboard 3 - Battery Lid cover 4 - Serial Output RS-232 5 - Protection lids for field protection usage 6 - AC Adapter output 7 - BNC Connector: pH Electrode Inlet

8 -BNC Connector: Thermocompensator Inlet

Equipment Operation

To turn ON the equipment, press and hold key. Make sure the power cord is plugged correctly! The menus are self-explanation with it’s respective options, selected by pressing the key. After making your selection(flashing option), using key, press the key to confirm Your selection. This manual will represent the Flashing Option always in . In case of any error or if you decide to change your selection, press the key to move the screen one step back so you can make the necessary changes, or hold this key for about 5seconds in order to turn OFF the equipment, until the message “SWITCH OFF? YES / NO” shows off on screen.

SETUP OPERATION

This equipment is supplied with a non-volatile memory (E2PROM), to store it’s operational set up (resolution, reading mode, calibration, etc). Even if disconnected from it’s power supply, it will not loose the information saved for work! Before you start to work with this equipment, please review the setup, so you can program the equipment based on your application! After powering the equipment on, by pressing and holding key, the equipment will perform an Auto Check and will then stop at Main Menu(Select Function) with options for the user to Select the desired Function. pH function will be flashing as a default. Press key to move around until you reach the desired selection(flashing option) then press key to access the sub-menu were you will find the SETUP FUNCTION(SET.). Press the key until SET is flashing, then press key to confirm it. The equipment will prompt for a password, press the following keys in sequence

Always use key to move around the options and press key to confirm this option.

Refer to page 12 for description of Set Up Screens.

CHECK OPERATION

The Check Sensor option is very useful, it gives the user the conditions to check the sensibility of the sensor. The operation is self-explanatory! From main menu press the key to choose the desired function, then press key to confirm. Select option Check, then press key to confirm option. The display will guide you thru the process.

READING OPERATION

Under this operation, you’ll find CALIBRATION and READING options .If you want to calibrate the sensor, press the key to select the Calibration option(flashing option - CAL), then press key to confirm. The program will guide you step by step on how to calibrate the sensor. If you need to use the READING option, press the key to select READ (flashing option), then press key and the display will show the following format:

<ENTER>

<ENTER>

Blue Color

<ENTER>

<ENTER>

and follow the instructions on the display.

<ENTER>

<ENTER>

1 - The Prompt signal will flick at each reading. 2 - The Measured Value and Reference Temperature(chosen at setup). 3 - Sample Temperature. 4 - Electrode’s Sensibility.

99% 25.0 ºC

8.96 pH @ 25.0 ºC

Equipment Operation (cont.)

IMPORTANT INFORMATION

1 - In case you want to quit Reading operation, press and hold key for about 5 seconds in order to be recognized by the equipment. This time is necessary to certify the user desires to quit this mode. 2 - When the equipment is turned on again, the set up will follow initial conditions including the changes prior to when it was turned off. To turn off the equipment, press and hold key until the message to Switch Off shows on screen, then by pressing key, choose YES to turn if off or NO to continue working and press

<ENTER>

BASIC OPERATION The menus are self-explanatory for easy operation. To input new information or change the pre-seted information, the menu offers flashing options, selected by key and confirmed by . The key is used to change options or to correct data (every time the user press The screen will move back one step or one option). This manual will represent the Flashing Option always in .

key to confirm the option chosen.

BLUE Color

<ENTER>

+ 26 hidden pages

Omega PHB21 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual