The GAOTek Multi-Parameter Water Quality Meter (pX and pH, Conductivity) is designed with 200 sets of data storage and the pX/pH measure the potential (mV), pH, pX and ion concentration. It provides ion measuring modes with appropriate ISE electrode and reference electrode for convenient measurement. It has automatic buffer group management of 10 kinds standard buffers and allows users to choose appropriate buffers. It supports multi-point (up to five-point) calibration. This water Quality meter is equipped with chip microprocessor and highly accurate A/D converter. It is capable of measuring DO concentration, DO saturation and electrode current. It complies with GLP standard.
- pH/pX measuring module allows measurement of potential (mV), pH, pX and ion concentration
- Provides many ion measuring modes with appropriate ISE electrode and reference electrode for convenient measurement.
- Automatically recognizes 10 kinds standard buffers
- Supports buffer group management and allows users to choose appropriate buffers or establish specific buffer group
- Supports one-point calibration, two-point calibration and multi-point (up to five-point) calibration
- Supports direct reading of concentration measurement
- Equipped with chip microprocessor and highly accurate A/D converter chips guarantees measuring accuracy
- Supports measurement of conductivity, resistivity, TDS and salinity, automatic temperature compensation, auto calibration, auto switch of range and frequency in the full of range
- Supports Calibration function. Users can calibrate cell constant or TDS factor
- Measures DO concentration, DO saturation and electrode current
- Performs automatic temperature compensation
- Calibrates zero-oxygen, full scale, barometric pressure and salinity
- Dot-matrix LCD displays data clearly
- Measures ion parameter, conductivity, DO and temperature values simultaneously
- Supports to record all procedures of operation, record and print calibration data
- Store 200 sets of pH data, conductivity data, TDS data, salinity data and DO data respectively
- Enables to View, print and delete measuring data
- Supports USB interface which is equipped with specific communication software to connect to the computer
- Supports electricity cut off protection function in case the meter is turned off to protect the stored measuring data, calibrating data and set parameter
- Backlight enables users to use in darkness
- PC panel and touch key ensures reliability and long life
|Range||-2.00 pH/pX ~ 20.00 pH/pX|
|Accuracy||±0.01 pH ± 1 bit|
|Stability||(±0.01 pH/pX)/3 h|
|Range||-1999.9 mV ~ 1999.9 mV|
|Accuracy||±0.01 % FS|
|Range||0.000 μS/cm ~ 199.9 mS/cm|
|Accuracy||±1.0 % (FS)|
|Stability||±0.5 % (F))/3 h|
|Range||5.00 Ωcm ~ 20.00 M Ωcm|
|Accuracy||±1.0 % (FS)|
|Range||0.000 mg/L ~ 100.0 g/L|
|Accuracy||±1.0 % (FS)|
|Range||0.00 ~ 8.00 %|
|Range||0.00 ~ 19.99 mg/L|
|Range||0.00 ~ 199.9 %|
|Accuracy||±10.0 % FS|
|Range||0.00 mg/L ~ 19990 mg/L|
|Range||23 °F ~ 221°F (-5.0 °C~ 105.0 °C)|
|Resolution||32.18 °F (0.1 °C)|
|Accuracy||±0.3 °C ±1 bit|
|Data Storage||200 sets of data|
|Power Supply||Universal power adaptor (9 V DC, 800 mA)|
|Dimensions||11.02 in × 8.46 in × 3.66 in (280 mm × 215 mm × 93 mm)|
|Weight||2.20 lbs (1 kg)|
|Relative Humidity||<=85 %|
|Temperature Compensation||pH||32 °F ~ 212 °F (0 °C ~ 100 °C)|
|Conductivity||32 °F ~ 212 °F (0 °C ~ 100 °C)|
|DO||32 °F ~ 104 °F (0 °C ~ 40 °C)|
Structures Front panel of the instrument
- Electronic unit
- Electrode holder
- ATC probe
- ISE electrode
- Conductivity probe
- DO probe
The instrument has two systems: one is electronic unit and the other is electrode system. The electrode system is composed of ISE electrode, conductive probe, DO probe and ATC probe.
Rear panel of the instrument
There are 8 sockets on the rear panel.
7) ATC probe
9) ISE or ATC electrode
10) Reference electrode
11) Conductive probe
12) DO probe
The instrument has 15 keys. They are 1/OUTPUT 2/▼, 3/SAVE, 4/<, 5/SETUP, 6/>, 7/VIEW, 8/▲ , 9/MODE, 0/MEASURE, ./CALIB, -/DELETE, ENTER key, CANCEL key and ON/OFF key.
Except ENTER key and CANCEL key, others are double-function key.
Only when user input data, they work as number key.
- 1/OUTPUT key: Pressing this key can input ‘1’; pressing this key can output stored data orcalibration data when users view them.
- 2/▼ key、4/< key、8/▲ key、6/> key: Pressing these keys can input“2”,“4”,“8”and“6”; ▼and▲ can select manual.
- 3/SAVE key: This key can input “3”; the key can save measuring result.
- 5/SETUP key: This key can input“5”; the key can set up different function under different operation.
- 7/VIEW key: The key can input“7”; the key can also view stored data or calibration data.
- 9/MODE key: The key can input“9”; the key can also switch function or parameter.
- 0/MEASURE key: This key can input“0”; the key can also do measurement in the initialstate.
- ./CALIB key: This key can input ‘.’; this key can also calibrate slope and cell constant.
- -/DELETE key: This key can input ‘-’; this key can also delete stored data when user viewit.
- ON/OFF key: Turn on or off the instrument.
- a) The connection of electrodes
- Measure different parameters to select different electrodes:
- Measuring pH value needs pH electrode;
- Measuring other ions needs other appropriate ion-selective electrodes;
- Measuring conductivity, TDS and salinity needs conductive probes;
- Measuring DO and saturation needs DO probes;
- Measuring temperature needs temperature sensor.
Users can select appropriate electrodes according to different needs.
Measuring temperature has two methods:
- Using temperature sensor or DO probe. That is to install temperature sensor or DO probeon the socket of DO probe;
- If there is not any electrodes connected with DO probe socket, meter will do manualtemperature compensation. The detailed method will vary with different parameter.
- b) USB communication line connection
If user hopes to use software, user can connect USB communication line with computer.
User can finish communication after installing software correctly.
When the instrument is in power supply, it can be turned on automatically.
- Press ‘On/Off’ key to turn off.
- Disconnect the power adapter if the instrument is not in use for a long time.
The initial state is like the above picture. The left area displays current system time. The rightarea displays measuring modes and measuring parameter.
In the initial state:
- Press ‘SETUP’ key to set up measuring modes and ion modes;
- Press ‘VIEW’ key to view measuring parameter and stored data;
- Press ‘MEASURE’ key to do measurement.
Different instruments support different measuring modules. When users choose function module which instrument doesn’t support, the instrument will remind user of that. The information will be displayed like the picture below: All function modules notifies about the unsupported instrument by reminding message.
Set up function in the initial state
Set up ‘Measuring Mode’, ‘Set Ion Mode’, ‘Date & Time’, ‘Manual Temperature’, ‘Balance Condition’ and ‘Parameter Setup’ in the initial state.
- Press ’SETUP’ key displaying setup menu. It is displayed as the above picture.
The instrument reversely display menu.
- Choose appropriate item;
- Press ‘ENTER’ key to select relative function module;
- Press ‘CANCEL’ key to exit from menu.
‘Set up Measuring Mode’: Set up current measuring mode (Continuous Mode, Timed Reading Mode, Balance Reading Mode or Ion Concentration Mode) and measuring parameter.
‘Set up System Time’: Set up system time.
‘Set up Manual Temperature’: Measure temperature manually if the instrument is not connected with temperature sensor.
‘Set up Balance Condition’: Set up balance condition in the balance mode.
‘System Setup’: Set up necessary GLP.
‘Parameter Setup’: Set up current parameter.
Set up measuring mode (SET MODE and PARA)
Except ion concentration, the instrument can do measurement simultaneous among ion module,conductivity module and DO module. The meter displays three modules: The major module display measurement value, auxiliary parameter and current temperature value. Other two modules display a measurement value. Measuring according to set up last time.
User can select single module or parameter. The instrument also supports three measuring modes including Continuous Mode, Timed Mode and Balance Mode; Ion concentration supports direct concentration reading.
User chooses a major parameter of certain module in actual measurement. The instrument will still allow user to view all the parameters contained in this module. For example, user will choose conductivity in conductivity module. During measurement, users can also view, save and print other parameter such as TDS and salinity. (Except pH and pX)
- Press ’SETUP’ key and ’ENTER’ key to set up measuring mode. It displays as the picture.
The left area is parameter row including pH, pX, conductivity, TDS, salinity, DO, saturation andion concentration.
The right area is measuring mode including Continuous Mode, Timed Mode and Balance Mode. The item with “√” indicates currently chosen measuring parameter or measuring mode. The reversely displayed item indicates current cursor position;
- Press arrow keys to move cursor;
- Press ’SETUP’ key to choose it or cancel it when the cursor moves to the appropriate item;
- Press ‘ENTER’ key to return to the initial state and the meter saves current setting automatically. The instrument can support up to 3 major parameters simultaneously.
The picture below is displayed when user choose measuring parameter.
The data displayed by LCD will vary with the change of major measuring parameter. Each
Measuring module has an independent measuring unit showing measuring parameter name and measuring result.
To help users to view other parameter of every module, the instrument sets up a special viewing function.
- Press ‘MODE’ key displaying the first unit reversely in the measuring mode. It indicates user have chosen the first.
- Press ‘MODE’ key repeatedly to choose the second or the third unit in order;
- Press “8/▲”key or“2/▼”key and switch the chosen to the first.
- Press “4/<” key or “6/>” key repeatedly to view other measuring parameter of current module.
For example, when the current measuring module is conductivity module and current parameter is conductivity, if user presses “4/<” key or“6/>” key repeatedly, cursor will move among TDS, salinity, resistivity and conductivity. (Note: This method is not suitable to ion module.) After viewing, if user does not press key continuously in a few seconds, the instrument will exit from viewing state.
This is the most used measuring mode. When measurement begins, the meter performs measurement, calculation and displays measuring result continuously. User can view calibrated parameter, calibrate electrode, save, or print measuring result during measurement.
- Press ’CANCEL’ key and then press ‘ENTER’ key to exit from measuring mode.
Timed Reading Mode (Timed Reading)
Timed Reading Mode is designed for convenient check. For example, if user needs to measurepH continuously for 30 minutes. Set time interval first. When measurement begins, meter will automatically measure, calculate and display measuring result. When the set measurement time period is over, the meter will automatically save measuring data (If its USB is connected with PC, the meter will automatically print out the measuring data). Then the meter begins next measurement automatically.
- Press ’CANCEL’ key and then press “ENTER” key to exit from Timed Reading Mode.
The default setup for time interval is 10 minutes.
Balance Reading Mode (Balance Mode)
Set up balance condition at first. When the measurement begins, the meter will automatically measure, calculate and display measuring result. When the measurement meets preset balance condition, the measurement finishes.
During a measurement in Balance Mode, user can view measuring parameter and calibrate Electrode. After measurement, user can save and print out measuring result.
- Press ‘CANCEL’ key to exit measuring mode;
- Press ‘MEASURE’ key to begin next measurement
Set Ion Mode (SET ION MODE)
The instrument provides 10 regular kinds of ion modes for various ion measurements, allowing user to choose appropriate ion mode to do certain concentration measurement. After measurement, user can view current ion concentration according to different ion concentration unit.
- Press ’SETUP’ key to select ‘SET ION MODE’;
- Press ‘ENTER’ key to enter ‘SET UP ION MODE’.
The ion mode is divided into three parts: Regular Ion (First and Second) and Custom Ion. The
Instrument provides some regular ion modes. They are H+, Ag+, Na+, K+, NH4+, Cl-, F-, NO3-, BF4-,CN-, Cu2+, Pb2+ and Ca2+ .(H+ ion is not displayed in ion mode because it is allowed in measurement all the time.) It displays ion name and molecular weight on the bottom of LCD.
- Move cursor to select relative ion (it is displayed reversely.);
- Press ’ENTER’ key and the instrument regard the selected ion mode as actual ion mode;
- Press ‘CANCEL’ key to exit from ion mode and return to initial state.
User can establish specific ion mode(Custom Ion). Only if user has relative ion selective electrodes to measure ion concentration according to operation of regular ion modes.
- Press ’SETUP’ key directly to establish new ion if there is no Custom Ion (Shown is as follow picture)
The instrument supports up to 5 kinds of custom ion modes, which are from Cus00~Cus04.
User can set up weight and valence of ion.
- Press ’ENTER’ key after setting up;
- Move the cursor to Custom(custom ion);
- Press ’SETUP’ key and select ‘Create New Mode?’, ‘Amend Ion Mode ’ or ‘Delete Ion
User can begin concentration measurement after they select correct ion mode. If user selects improper ion mode, the measurement value will be incorrect.
For example, if user need to measure sodium concentration:
- Select ‘Na+ ion mode’ in ‘SET ION MODE’;
- Measure sodium ion concentration.
Set up system time
Set up time:
- Press ’SETUP’ key to select ‘SET DATE & TIME’;
- Press ’ENTER’ key to set up current system time.
The meter displays current time including ‘year’, ‘day’, ‘hour’, ‘minute’ and ‘second’.
- Move the cursor to the time item;
- Press ‘SETUP’ key to input relative time value.
For example, if user needs to set up current month information, user can operate according to following method:
- Press arrow keys to move cursor to ‘MM’ item;
- Press ‘SETUP’ key and the meter will display a prompt window;
- Input the current month information;
- Press ‘ENTER’ key to exit from input window;
- Press ‘ENTER’ key to finish setting after modifying all the time item;
- Press ‘CANCEL’ key to exit from system setting module and return to the initial state.
User can also modify other time according to this method.
Set up manual temperature (Set Manual Temp)
If the temperature sensor socket is connected with temperature sensor, the instrument will measure temperature automatically. On the contrary, the instrument will take the manual temperature ascurrent temperature.
- Press ‘SETUP’ key to select ‘Set Manual Temp’;
- Press ‘ENTER’ key and the instrument will enter manual temperature setting module;
- Press ‘SETUP’ key to modify manual temperature;
- Input temperature value by user.
Set up balance condition
Balance measuring condition is matched with balance measuring mode. The picture shows the balance condition of pX is 0.010 pX. When the variation of pX (including pH) is smaller than 0.010 pX, we can regard this measurement effective.
When user selects balance measuring mode and all the measurement complies with balance
condition in balance time, this measurement will finish. Balance time is effective only to balance measuring mode. The unit is second (s) and the range is 1~200 seconds.
The function includes GLP standard, electrode calibration interval and system time.
- Press ‘SETUP’ key to select ‘System Setup’;
- Press ’ENTER’ key to enter system setting module;
- Press arrow keys to move the cursor to the item and modify the relative parameter;
- Press ‘CANCEL’ key to exit from setting state and return to the initial state.
Electrode calibration interval refers to the time interval which instrument reminds users calibrating electrode. The instrument will calculate the calibration time from last to now. If the time period oflast calibration exceeds preset calibration time interval, the instrument will display a prompt window and remind user to recalibrate electrodes. The instrument takes hour (hr) as the unit for electrode calibration. The time interval of pH electrode calibration is 4 hours.
Operator No. is three-digit number, and the range of number is 000~200. All operation recordincludes Operator No.
Automatic deletion of stored data refers to that the stored data will be covered when stored datareaches the preset volume.
For example, the instrument can store 200 sets of pH data. However, when the 201st set of data isstored, it will be stored in the first data position. The data will be stored from beginning. Otherwise,the meter will not save measurement data.
User can set up system time in this state as following:
- Move to time item;
- Press ‘SETUP’ key.
User can view current measuring parameter, modify measuring parameter and view stored data in any time. The current measuring parameter includes data of last calibration and current parameter.
- Press ’VIEW’ key in the initial state and select to view, modify measuring parameter and view stored data.
View pH Measuring Parameter (View pH Para)
This function can view pH calibration data in the initial state.
- Press ’VIEW’ key to select ‘View pH Para’;
- Press ’ENTER’ key to view pH measuring parameter.
The last calibration data is displayed on the top of the meter including calibration time, buffer number and calibration data. The current buffer group is displayed on the bottom area ofthe meter. When last calibration adopts multi-point calibration, users can press arrow keys to showdetailed data of every buffer.
User can recalibrate electrode slope print calibration data and set new buffer group.
- Press ‘CANCEL’ key to exit from viewing module;
- Press ‘OUTPUT’ key to print calibration data out if users need to print current calibration data out and connect computer by USB.
Set up buffer group (Select Group)
The instrument can automatically recognize 10 kinds of buffer solution. The instrument can do multi-point (up to 5 point) calibration. Since there is overlap of pH range among 10 kinds of buffers, users need to establish certain buffer group to ensure measuring accuracy.
For example, user can choose 4.003 pH and 9.182 pH buffers as a buffer group to calibrate
electrode slope. Then the instrument will recognize these two buffers in actual calibration.
- Press ‘SETUP’ key to set up current buffer GROUP in mode of ‘Select Group’ as shown in above picture.
The current buffer group is buffer group 1. The system provides three buffer groups. They are GROUP 1, GROUP 2, and CUSTOM. The GROUP 1 contains 4.000 pH, 6.864 pH and 9.182 pH; GROUP 2 contains 3.776 pH, 7.000 pH and 10.012 pH; CUSTOM allows user to choose up to 5 buffers.
- Press arrow keys to switch buffer group;
- Press ‘ENTER’ key to exit from setting buffer group and return to viewing calibration data module.
- Move the cursor to select ‘Set Custom Group’;
- Press ‘SETUP’ key to set up custom group.
There are 10 icons which are relevant to 10 kinds of standard buffers (as shown in above picture).
They are 1.679 pH, 3.557 pH, 3.776 pH, 4.003 pH, 6.864 pH, 7.000 pH, 7.413 pH, 9.182 pH, 10.012 pH and 12.454 pH. There displays pH value under every icon. The icon with stick indicates that this buffer has been chosen. The icon without stick indicates it hasn’t been chosen; the icon displayed in reverse color indicates the current buffer is usable.
- Press it again to choose or delete current buffer.
On the bottom of the meter displays pH range of relative buffers.
- Press arrow keys and move cursor to user’s need buffer;
- Select the item(or clear the chosen item).
For example, choose pH 3.557 buffer:
- Move the cursor to icon of 3.557 pH;
- Press ‘SETUP’ key, the icon 3.557 pH will be shown with stick.
In order to avoid overlap of pH value, it is better to select corresponding buffer. With regard to other buffers users don’t use, user should cancel the chosen items.
View pX Measuring Parameter (View pX Para)
- Press ‘VIEW’ key in the initial state;
- Select ‘View pX Para’ and press ‘ENTER’ key to view pH measuring parameter. (the picture is shown as following)
On the top of the meter shows the last calibration data including calibration time, calibration point and calibration data to every point.
On the bottom of the meter shows current set ion mode.
- Press arrow keys to display detailed data of every buffer point when last calibration adopts multi-point calibration
- Recalibrate electrode slope, print calibration data out and set up new calibration group.
- Press ‘OUTPUT’ key to print calibration data out if user needs to print current calibration data. User can connect computer by USB.
- Press ‘CANCEL’ key to exit from viewing calibration data.
View conductivity measuring parameter (View COND Para)
- Press ‘VIEW’ key in the initial state
- Select ‘View COND Para’ and press ‘ENTER’ key to view conductivity measuring parameter. (the picture is shown as following)
On the top of the meter shows last calibration data.
On the bottom area of the meter shows conductivity parameter including cell constant (Cell
Const) and temperature coefficient (T. Coef).
- Press ‘OUTPUT’ key to print calibration data out if users need to print current calibration data. User can connect computer by USB.
Set up cell constant
Generally there is cell constant value on every conductive probe of our company. After setting the cell constant value, user can do normal measurement. After a period of using, if user doubts the accuracy of cell constant, user can recalibrate it with standard conductivity solution.
- Press ‘CALIB’ key to calibrate it directly
- Generally there are two methods which can calculate cell constant value; one method is to recalibrate the electrode with standard conductivity solution. The instrument will automatically calculate cell constant when calibration finishes. The other method is to directly set up cell constant.
- Press ‘SETUP’ key to select ‘Setup Cell Const’(setup cell constant), the meter will display a prompt window;
- Input new cell constant.
Set up temperature compensation coefficient (Setup Temperature coefficient)
During conductivity measurement, the change of temperature will cause inaccurate measurement. At this moment, we need to set temperature compensation coefficient. The default value is 0.020.
- Press ‘SETUP’ key when user view conductivity measuring parameter
- Select ‘Setup T. coef’, the instrument will display a prompt window
- Input new temperature coefficient
- Press ‘ENTER’ key
View TDS measuring parameter (View TDS Para)
Viewing TDS measuring parameter is similar to viewing conductivity measuring parameter.
User can set up new TDS coefficient according to user’s actual need and can also set up
temperature compensation coefficient.
View DO measuring parameter (View DO Para)
On the top shows last calibration data. The bottom area shows the current barometric pressure (Air P.) and DO salinity (SALI F.). It is shown in the picture.
- Press ‘VIEW’ key in the initial state;
- Select ‘View DO Para’;
- Press ‘ENTER’ key to view DO measuring parameter.
Modify barometric pressure or salinity:
- Press ‘SETUP’ key;
- Select ‘Air P.’ or ‘SALI F. ’.
View stored data
After measurement, user can save measuring result for viewing and printing.
The instrument can store 200 sets of pH value, conductivity, TDS, salinity, DO and saturation
which meets GLP standard. Except H+, user can do pX and concentration measurement for other ions. pX parameter and concentration will be saved respectively.
For example, when user measures sodium ion concentration with Na+ mode, the instrument will store measuring data. The meter can store 100 sets of pNa measuring data and 100 sets of concentration measuring data;
The following picture shows stored pH data. On the top shows corresponding mode name and actual data number. It can show up to 10 stored data in every page. The contents shown include storing time and operator number.
- Press ‘VIEW’ key in the initial state;
- Select item in the menu ‘View pH Rec’ and view corresponding stored data (Shown as the above picture) ;
- Press arrow keys to view every stored data.
Print and delete stored data:
- Press ‘OUTPUT’ key and ‘DELETE’ key.
View pH or ion concentration data:
- Press ‘SETUP’ key and switch to view stored data in other ion modes.
The principle of ion measurement is to insert ion-selective electrode and appropriate reference electrode in the sample solution to form electrochemical system.
This is the most commonly used ion measuring mode.
- Press ‘MEASURE’ key in the initial state to begin measurement in pH measurement state;
- Or press ‘SETUP’ key to select measuring modes and pH measuring parameter.
When the meter enters pH measuring state, the middle of the meter will display current measuring mode, system time, pH measuring data, corresponding potential value and temperature value. The bottom of the meter displays last calibration data.
During measurement, user can calibrate potential zero, view pH save data, calibrate pH electrode, save or print measuring data.
- Press ‘SAVE’ key to save current measuring data when the measuring data becomes stable;
- Print current measuring data if the USB is connected with computer.
Time Mode: The meter will automatically measure, calculate and display measuring data. When it reaches the time interval which users set, the meter will automatically save measuring data. If USB is connected with computer, the meter will automatically print measuring data. The meter can also begin next measurement after printing the data.
Balance Mode: The meter will automatically measure, calculate and display measuring result. When the measurement data meet the pre-setbalance condition, this measurement is finished. At this moment, user can press ‘SAVE’ key tosave current measuring result; If USB is connected with computer, user can print current measuring data.
- Press ‘CANCEL’ key to finish measurement.
pH electrode calibration
- Calibrate electrode before each measurement. After calibration, the last calibration data will be covered.
- Recalibrate electrode when the electrode is used for a period of time.
- Remind to calibrate the electrode when set the calibration time as appropriate interval.
The pH calibration of meter is shown in the following picture. The meter displays current
measuring data on the top including current pH value, potential value and temperature value (Slope is set as 100 %.) On the bottom area displays current calibration data.
Automatic or manual recognition indicates current recognition method.
- Press ‘SETUP’ key to select recognition method or set up current buffer groups;
- Press ‘ENTER’ key when the electrode is put into the buffer solution and the meter displays stably, user can calibrate current buffer;
- Press ‘CANCEL’ key to exit from calibration.
The meter has auto-recognition function. It can automatically recognize 10 kinds of standard
buffers. Since the pH range of 10 kinds of buffer may have some overlaps. In order to insure
measuring accuracy, user should check buffer groups before calibration.
For instance, if user wants to calibrate electrode slope with 4.003 pH and 9.182 pH standard buffers, user must set the two standard buffer groups as 4.003 pH and 9.182 pH. Otherwise the meter will not automatically recognize the two buffers.
- Press ‘SETUP’ key in calibration state;
- Select ‘Select Group’.
The procedure of calibration is listed as below:
- Prepare 1 to 5 standard buffer groups before calibration, user can (They can be regular standard buffer solution or can be prepared by users.);
- Put them in the constant temperature for a period of time;
- Setup buffer group .If the buffers are not regular standard buffer solution, select manual recognition method according to ‘Select Group’.
- Rinse pH electrode, reference electrode and temperature sensor clean and put them in buffer solution to be calibrated.
- Press ‘ENTER’ key after the display becomes stable. Then the meter displays ‘Save data…’and saves calibrated data.
- Later, the meter will remind user ‘Continue Calib?’ If users need to calibrate other buffer solution, they can select to continue calibration and repeat previous procedure until the calibration finishes. During calibration, users can press ‘CANCEL’ key to finish calibration.
- The meter supports up to 5 point calibration. When the meter begins to calibrate the 5th buffer and user can press ‘ENTER’ key, the meter will finish calibration automatically.
With regard to buffer solutions such as 6.864 pH and 7.000 pH buffers which pH range has overlaps, it is recommended user adopts the following method:
- The first method: When user calibrates buffer solution of 6.864 pH, select custom group. It is better to set the custom group as the one with only 6.864 pH and begin calibration. After calibrating buffer with 6.864 pH, set custom group again and set it as 7.000 pH. Then user cando calibration.
- The second method: Adopt manual recognition method for calibration. It means user should input pH value of the buffer solution at current temperature during each calibration for buffersolution. This method can also calibrate buffers but it’s a little complicated.
With regard to regular standard buffers, user can apply auto-recognition function. The meter will automatically recognize these standard buffer solutions. User doesn’t need to change the recognition method. (If the meter cannot recognize the solution, the meter will remind users: Calibration data is wrong. Users should replace electrode and set up buffer solution again. They can switch the auto-recognition method to manual recognition method. Users can select different operation according to actual condition.)
When user use standard buffers (irregular standard buffers to calibrate electrodes, user must adopt Manual-Recognize method.
For instance, the pH buffer at 77 °F (25.0 °C) is 2.704 pH, 2.710 pH at 77.18 °F (25.1 °C), and 2.720 pH at 77.36 °F (25.2 °C). User should keep the temperature value at 77 °F (25.0 °C) as soon as possible. When calibration begins, set manual recognize method. When the display of meter becomes stable, press ‘ENTER’ key and input STD pH value at present temperature. If the present temperature is 77.36 °F(25.2 °C), input 2.720. Press‘ENTER’ key and the meter save present calibrated data. Other buffer calibration is also performed in these steps.
If users have both regular and custom buffers, auto-recognition method for regular buffers and manual recognition method for custom buffer.
Adjust mV Zero
To guarantee accuracy of meters, user should adjust mV zero before measurement.
- Press ‘SETUP’ key to select ‘Adjust mV Zero’;
- Press ‘ENTER’ key. The meter will display a prompt window (‘Adjust mV Zero?’) and
- remind user to confirm it;
- Press ‘ENTER’ key to calibrate mV zero;
- Press ‘CANCEL’ key to give up operation and return to measuring state.
Each ion mode is corresponded to one kind of pX measurement. Selected corresponding ion mode, user can perform pX measurement.
For instance, if user has sodium ISE electrode and want to measure Na+ concentration:
- Select ‘Na+ ’from ‘SET ION MODE’ and measure sodium ion concentration.
- Check if the current ion mode is consistent with sample solution and ion selective electrode before each measurement.
- Press ‘MEASURE’ key to begin measurement when the parameter is pX in the initial state;
- Press ‘SETUP’ to select pX measurement parameter from ‘SET MODE & PARA’.
The meter displays shown in diagram. The interface and operation is as same as ‘pH Measuring Mode’. The measuring method and display will vary with different measuring modes. During measurement, user can recalibrate electrode and set parameters. After measurement, user can save and print measuring data.
- Press ‘CANCEL’ key to end measurement.
Calibrate Ion Selective Electrode
Before each measurement, recalibrate the electrodes. When the new calibration begins, the last calibrated data will be covered. Electrodes should be calibrated after a period of use.
In pX measurement, press ‘Calibrate’ key to select ‘pX Electrode’. Then press ‘ENTER’ key to
calibrate electrode slope. The meter enters calibration mode shown in the diagram.
The top shows the current pX (The slope is set as 100.00 %), potential, temperature value and current pX concentration. The bottom area shows current calibration result.
Before calibration, user should prepare 1~5 buffers (They can be common buffers purchased or can be special buffers prepared by user.) Put them in constant temperature environment for a certain period of time. The calibration procedures are listed as:
- Clean the corresponding ISE electrode (or reference electrode) and ATC probe, and put them in buffers to be calibrated.
- Press ‘SETUP’ key to select STD buffer value, user manually inputs STD pH value of selected buffer at selected temperature.
- When the reading becomes stable, press ‘ENTER’ key and the meter will display ‘Storing……’and save calibration data.
- After a few seconds, the meter will display a prompt window to remind user ‘Continue?’ It is shown in the picture. If user needs to calibrate other buffers, select the buffer user need to continue.
- Press ‘ENTER’ key to repeat previous procedures to calibrate another buffer until all buffers planned to be calibrated are calibrated.
- During calibration, user can press ‘CANCEL’ key to end calibration at any time.
- During calibration, if user replaces the new buffer, remember to input current STD buffer value.
- After the calibration of the 5th buffer, the meter will automatically finish the calibration.
Ion Concentration Measurement
It is used to measure ion concentration. This meter supports Direct Reading (Direct reading of concentration mode)
Direct Reading of Concentration Mode (Direct Reading)
The mode has following Nernst formula:
E x= E 0 + S× log(C x + C b)
In which: Ex~Equilibrium potential of sample;
E0 ~ zero potential, potential for ion activity being one.
S ~ electrode slope
Cx ~ concentration value of sample
Cb ~ blank concentration value.
User can obtain slope and zero potential through slope calibration and then can measure concentration of sample directly. If user need to measure blank concentration, select blank concentration measurement.
Select corresponding ion mode according to ISE (Ion Selective Electrode) type. For instance, if user wants to measure Ag+ concentration, select Ag+ mode. Set ion concentration as current parameter and select Direct Reading. Then press ‘ENTER’ key to return to initial state. Press ‘Measure’ key to perform Direct Reading which is shown in the diagram.
The upper left area shows current system time, potential, temperature and corresponding pX value. The bottom area shows current measuring result and blank concentration value.
If necessary, user can perform blank concentration correction.
During measurement, user can view calibrated data, calibrate electrode, and adjust mV zero.
Rinse ion selective electrode thoroughly and put it in sample solution. The meter displays present measuring data. When reading becomes stable, press ‘ENTER’ key and the meter will calculate measuring result as shown in diagram. Press ‘Save’ key to save present measuring result. Press‘Measure’ key to perform next ion concentration measurement. Press ‘CANCEL’ key to exit from direct reading mode of concentration and return to initial state.
If user needs to select concentration unit, press ‘SETUP’ key and select proper concentration unit.
Blank Concentration Calibration in Direct Reading Mode (Calib Blank
If user needs to calibrate blank concentration, choose blank concentration calibration. When the meter enters ‘blank concentration calibration’ the display is similarly to direct reading mode of concentration as shown in diagram.
After preparing blank solution, put corresponding ion selective electrode and ATC probe in solution. When reading becomes stable, press ‘ENTER’ key and the meter will calculate blank concentration value and save it automatically. Press ‘CANCEL’ key to return to direct reading mode ofconcentration.
During calibration, user can press ‘CANCEL’ key to exit from calibration at any time and return to direct reading mode of concentration.
- During blank calibration, the blank solution should have similar chemical composition with the sample solution
- Both Direct Reading Mode of Concentration and Standard Addition Mode have blank calibration. The detailed operation is as same as this direct reading of concentration mode.
Reset Blank Concentration
If user wants to clear last blank concentration value, select this function.
This meter can measure conductivity, resistivity, TDS and salinity. Within the whole measuring range, the meter will automatically perform automatic temperature compensation, auto-calibration, automatic switch of range and frequency.
When measuring conductivity and TDS with an ATC probe connected to the meter, originalvalue will be temperature compensated to change into the corresponding value in 77 °F (25.0 °C) according to the set temperature coefficient. If no ATC probe is connected, the original reading will be displayed without temperature compensation.
When measuring salinity with an ATC probe connected to the meter, original value will be temperature compensated to change into the corresponding value in 64.4 °F (18.0 °C) according to the set temperature coefficient. If no ATC probe is connected, the original reading will be displayed without temperature compensation.
User should pay attention to the following aspects before conductivity measurement:
The selection of conductivity probe
For conductivity probes with cell constant K=1.0 and K=10, one kind has platinum black
coating on platinum sheet and the other does not have platinum black coating on platinum sheet, classified as “platinum black” and “bright” respectively. The probe with platinum coating is usually called as platinum black probe; Bright probe is suitable for wider measuring range, (0 ～3000 μS/cm). If conductivity is higher than 3000 μS/cm, the measuring error may be larger.
To measure high conductivity, use a conductivity probe with high cell constant. When
conductivity is ≥200.00 mS/cm, use a conductivity probe with cell constant= 5 or 10. When
conductivity is ≥500.00 mS/cm, use a conductivity probe with cell constant= 10.
The Form of Conductivity Range and Corresponding Cell Constant
|0.000 ~ 19.99 µS/cm||20.00 M ~ 20.0 K||0.01|
|0.20 ~ 200 µS/cm||2.00 M ~ 2.00 K||0.1|
|2.000 ~ 20 mS/cm||200 K ~ 5||1.0|
|20.00 ~ 200 mS/cm||20K ~ 5||10|
In the initial state, if user knows conductivity parameter, press ‘Measure’ key to measure it directly. Otherwise press ‘SETUP’ key to select measuring mode and conductivity parameter. The top of the screen displays current measuring mode and system time; the major window displays current conductivity, resistivity and temperature.
Measurement and display methods will change with different measuring mode to some extent. During measurement, user can recalibrate cell constant and set up parameter; After measurement, user can press ‘Save’ key to save data, press ‘Output’ key to print data out, or press ‘CANCEL’ key to end measurement.
Calibrate Cell Constant
When conductivity probes go out of factory, each of them is labelled with cell constant. If users have doubt on the correctness of cell constant, they can recalibrate it according to following procedures:
User should choose proper standard solution according to different cell constant and preparation method.
- If user connects the meter to a conductivity probe but not an ATC probe, the meter will take temperature value manually input as present temperature. If manual temperature is set at 77 °F (0 °C), conductivity value displayed is the value without temperature compensation.
- Rinse conductivity probe with distilled water or DI water.
- Soak the conductivity probe in the standard solution.
- Temperature of solution should be controlled at: 77 °F ± 32.18 °F(25.0 °C ± 0.1 °C)or 68 °F ± 32.18 °F(20.0 °C ± 0.1 °C)or 64.4 °F ± 32.18 °F (18.0 °C ± 0.1 °C) or 59 °F ± 32.18 °F (15.0 °C ± 0.1 °C).
- Press ‘Calibrate’ key and then select “Cell Const”. The meter begins cell constant calibration process.
- Press “Setup” key to set standard solution Value (STD Value), and input standard value listed in the table for corresponding solution and corresponding temperature.
- When reading becomes stable, press ‘ENTER’ key and the meter will calculate and set the new cell constant. Now, calibration is done. Press ‘CANCEL’ key and cell constant calibration ends.
KCl Standard Solution Used to Measure Cell Constant
|Cell constant (cm-1)||0.01||0.1||1||10|
|0.001||0.01||0.01 or 0.1||0.1 or 1|
Composition of Standard Solution
|Concentration (mol/L)||concentration by volume KCl(g/L) solution (20 °C)|
|0.01||Dilute 0.01 mol/L solution from 100 mL to 1 liter|
Relation between KCl Solution Concentration and its Conductivity (unit: μS/cm)
|15.0 °C||18.0 °C||20.0 °C||25.0 °C||30.0 °C|
During high TDS measurement, the conductivity probe with high cell constant is recommended. When TDS≥10.00 g/L, user must use the probe with constant cell K=5 or K=10. Choose the proper conductivity probe and set proper cell constant, temperature coefficient and TDS factor. If user wants to calibrate conductivity probe, user need to calibrate cell constant in the conductivity parameter state. User could only calibrate TDS Factor in TDS parameter state.
In the initial state, if user has selected conductivity module and conductivity parameter, user can perform conductivity measurement directly. Or user must select conductivity module from measuring mode first and perform conductivity measurement.
Calibrate TDS Factor
According to the nature and measuring range of sample solution, user may select proper standard solution
- Set correct cell constant: In the measuring mode, press ‘SETUP’ key to select cell constant. Set cell constant according to the cell constant labelled on conductivity probe; Or recalibrateconductivity probe to obtain new cell constant. Press ‘Mode’ key and repeatedly press ‘4/<’key or (‘6/>’ key) to select TDS Measuring mode.
- Press ‘Calibrate’ key, and select ‘TDS Factor’. Press ‘ENTER’ key to enter Calibration mode.
- Rinse the conductivity probe with distilled water or DI water.
- Control the solution temperature at 77 °F ± 32.18 °F (0 °C ±0.1 °C). Soak the conductivity probe in standard solution
- Press ‘SETUP’ key and select ‘STD Value’ and then press “Enter” key. Input corresponding data from the table, i.e., the TDS value of present standard solution.
- When the readings become stable, press ‘ENTER’ key and the meter will automatically calculate and set new TDS factor. Now, calibration is finished. Press ‘CANCEL’ key and exit from TDS factor calibration mode.
Relationship between conductivity and TDS standard solution
|Conductivity (μS/cm)||TDS standard value|
|KCl (mg/L)||NaCl (mg/L)||442 (mg/L)|
Note: The value listed in the form is the one at 77 °F (25 °C)
442 indicates 40 % Na2SO4, 40 % NaHCO3, 20 % NaCl.
Salinity Measuring Method
Select a proper conductivity probe before measuring Salinity. The selection principle is the same as the selection of conductivity probe. After user select a conductivity probe, user can set corresponding cell constant, in the initial state, if salinity parameters have been set, user can measure salinity directly. Or user can measure salinity after salinity parameter is set through ‘Setup Measuring Mode’ or description of display, measuring procedure and operation in salinity measurement. After measurement, user can press ‘Save’ key to save data, press ‘Output’ key to output measuring data, and press ‘CANCEL’ key to end measurement.
This meter can measure DO concentration, DO saturation, and electrode current. It can perform automatic temperature compensation, zero oxygen calibration, full scale calibration, air pressure calibration and salinity calibration.
If user is using this meter for the first time, rinse DO probe with distilled water and insert it in sample solution. The meter will perform measurement after start-up. This meter can calculate and display DO concentration, saturation or electrode current. If this is user’s first time to use DO probe, or user haven’t used DO probe for a long time, user needs to calibrate DO probe first.
In ‘Set Measuring Mode’, user may select DO module parameters such as DO and saturation which is shown in the diagram.
The top of the screen shows current measuring mode, system time, DO data, corresponding DO current value and temperature; the bottom area displays Last Calib (the last calibration data). The measuring and display methods vary slightly with different measuring mode. During measurement, user can calibrate probe, set parameter again. After measurement, user can save and output measuring data.
Pressing ‘CANCEL’ key can finish measurement.
Calibrate DO Probe
To obtain accurate measurement, DO probe must be calibrated before use. The meter contains multi-functions including Zero Point Calibration and Full Scale Calibration.
In DO measuring state, press ‘SETUP’ key and select ‘Calib DO probe’. Press ‘ENTER’ key tobegin calibration of DO Probe. It is shown in the diagram. The top of the screen shows current calibration state and calibration state and calibration time; the middle area shows DO probe current, DO concentration and current temperature. The bottom area shows calibration result. The diagram shows the state of zero calibration. Press ‘Mode’ key can switch zero oxygen calibration or full scale calibration.
Zero Point Calibration (Zero Oxygen)
Rinse DO probe with distilled water and put it in zero oxygen solution (5 % sodium sulphite solution or as described in instruction manual for the DO probe) When readings become stable, press ‘ENTER’ key and press it again. Meter will automatically record ZeroPoint value and then ends the Zero Point Calibration.
During calibration, press ‘SETUP’ key to set calibration parameter such as barometric pressure and salinity factor. Press ‘CANCEL’ key to end calibration and return to measuring state.
Full Scale Calibration (Full Scale)
Take the DO probe out of solution and rinse it with water. Absorb the moisture of the membrane surface. Put DO probe into air above the water in the container (e.g.: triangle flask), but don’t touch probe with water.
When the meter is in DO calibration state and readings become stable, press ‘ENTER’ key and meter will automatically record full scale value. Then the calibration of full scale ends.
During calibration, press ‘SETUP’ key to set parameters such as air pressure and salinity. Then press‘CANCEL’ key to return to measuring state.
|1||GAOTek Multi-Parameter Water Quality Meter (pX and pH, Conductivity)|
|2||Platinum Black Electrode|
|3||pH Combination Electrode|
|5||Multi-function Electrode Support Stand|
|6||pH Standard buffer Solution pH4, 7, 10|
|7||USB Communication Line|
|8||Data Collecting Software|