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Overview

GAOTek PH Meter with Conductivity/TDS/Salinity (Storage Data) is designed for six measurement modes to measure the pH, ORP, Conductivity, TDS, Salinity and Resistivity of the liquids .It provides the expanded memory storage and recalls up to 500 readings. It supports built-in real time clock to stamps the stored data and complies with GLP standard. This meter function continuously with multimode power scheme such as battery, USB port and power adapter. It provides the calibration due reminder to calibrate the meter regularly. The pH Meter equipped with a clear and bright LCD display used to display measured values, mode indicators and help message.

Key Features

  • Clear and bright LCD display used to display measured values, mode indicators and help message.
  • Automatic Temperature Compensation provides accurate reading over the entire range.
  • Calibration Due Reminder prompts user to calibrate the meter regularly.
  • Stability indicator automatically display current measurement status.
  • Auto-Hold function freezes stable measured value for easy viewing and recording.
  • Selectable temperature unit (°C or °F) meets different application requirements.
  • Manual temperature calibration corrects temperature deviation.
  • System menu allows setting the 12 parameters, including the number of calibration points,
    resolution, stability condition, measurement unit, etc.
  • Expanded memory stores and recalls up to 500 readings.
  • Built-in real-time clock stamps stored data to meet GLP standard.
  • Stored data can be transferred into computer by USB communication interface
  • Multi-mode power scheme (battery, power adapter, computer’s USB port)
  • Supports 3 connectors for connecting the various types of sensors

Technical Specifications

pH
Range -2.000 pH to 20.000 pH
Accuracy ± 0.002 pH
Resolution 0.1 pH, 0.01 pH, 0.001 pH (Selectable)
Calibration Points 1 to 5 points
Temperature Compensation 14 ˚F ~ 212 ˚F (0 ˚C ~ 100 ˚C)
Compensation Mode Manual or Automatic
Calibration Solutions USA, NIST, DIN or User-defined
mV
Range -1999.9 mV to 1999.9 mV
Accuracy ± 0.2 mV
Resolution 0.1 mV, 1 mV (Selectable)
Calibration Range ± 200 mV
Calibration Points 1 point (only for relative mV mode)
Conductivity
Range  0 µS/cm to 20 µS/cm

200 µS/cm

2000 µS/cm

20.00 mS/cm

200.0 mS/cm

Accuracy ± 0.5 % F.S
Calibration Points 1 point  to 5 points
Calibration Solutions 10 µS/cm, 84 µS/cm, 1413 µS/cm, 12.88 mS/cm,111.8 mS/cm
Temperature Coefficient 0.0 % to 10.0 % / °C
Compensation Modes Linear or Pure water
Cell Constant K=0.1, 1, 10 or User-defined
Normalization Temperature 68 ˚F  or 77 ˚F (20 ˚C or 25 ˚C)
Temperature Compensation 32 ˚F ~ 212 ˚F (0 ˚C ~ 100 ˚C)
TDS
Range 0 ppt to 100 ppt (max.200 ppt, depending on factor setting)
Accuracy ± 1 % F.S
TDS Factor 0.1 to 1.0 (Default 0.5)
Salinity
Range 0 ppt to 10 ppt (Max 80 ppt)
Accuracy ± 1 % F.S
Measurement Modes Seawater or Practical salinity
Resistivity
Range 0 mΩ to 100 mΩ
Accuracy ± 1 % F.S
Resolution 0.01, 0.1, 1
Temperature
Range 32 ˚F ~ 221 ˚F (0 ˚C ~ 105 ˚C)
Accuracy ± 0.5 °C, ± 0.5 °F
Resolution 32.18 °F (0.1 °C)
Calibration Points 1 point
Calibration Range ± 10 °C measured value
General Specification
Interface USB communication interface
Connector BNC, 6-pin mini plug
Memory Up to 500 sets
Calibration Due 0 to 31 days
HOLD Function Manual or Automatic
Stability Conditions Low or High
Reset Function Yes
Battery Type 1.5 V “AA” batteries
Battery Life 150 hours approximately
Dimensions 6.7 in × 3.35 in × 1.18 in (170 mm × 85 mm × 30 mm)
Weight 10.58 oz. (300 g)

Additional Information

ACCESSORIES:

  • pH Electrode
  • Conductivity Electrode
  • Dissolved Oxygen Probe
  • Temperature Probe
  • pH Buffer Pouches (pH 4.01, 7.00, 10.01)
  • Conductivity Calibration Solutions (84 μS/cm, 1413 μS/cm, 12.88 mS/cm)
  • DO Electrolyte Solution
  • DO Membrane Cap
  • Batteries

Display

This PH Meter with Conductivity/TDS/Salinity (Storage Data) is equipped with a clear and bright LCD display that shows measured values, mode indicators and help messages.

Keypad

The meter has a succinct membrane keypad, names and symbols describe the each function key controls.

Key Description
MEAS|
  • Power the meter ON/OFF.
  • Freezes the measured value on the display, press the key again to resume measuring.
  • In the calibration or setting mode, exits current mode and returns to measurement.
MODE|°C
  • Toggles between available measurements modes (pH, mV, ORP, Ion, Conductivity, TDS, Salinity, Resistivity, and DO).
  • Press and hold the key to enter temperature setting mode.
CAL|
  • Press the key to enter the calibration mode.
  • Press and hold the key to enter the setup menu.
MI|
  • Press the key to store current measured value.
  • Press  key in setup mode to scroll up through menu.
  • Press  key in temperature setting mode to increase the setting value.
MR|
  • Press the key to view calibration report or stored data.
  • Press  key in setup mode to scroll down through menu.
  • Press  key in temperature setting mode to decrease the setting value.
ENTER|
  • Confirms the calibration, setting value or displayed option.
  • Press and hold the key to turn On/Off the backlight.

Connectors

This PH Meter with Conductivity/TDS/Salinity (Storage Data) provides 3 connectors for connecting the various types of sensors. Listed in the below table are the details of these connectors.

No Connector Function
1 BNC Connector For connecting the pH, ORP or Ion Selective Electrodes
2 Phone Jack For connecting the temperature probe
3 6-pin connector For connecting the conductivity electrode or dissolved oxygen probe

Connecting the Sensor

Take out the sensor from the carrying case.

FOR THE pH, ORP OR ION SELECTIVE ELECTRODES:

Insert the BNC connector into corresponding connector socket. Rotate and push the connector clockwise until it locks.

FOR THE CONDUCTIVITY ELECTRODE OR DISSOLVED OXYGEN PROBE:

  • Insert the 6-pin connector into corresponding connector socket, ensure the connector is fully seated.
  • After connection is completed, DO NOT pull on the sensor cord. Always make sure that the connector is clean and dry.

Preparing the pH Buffer Solutions

PH Meter with Conductivity/TDS/Salinity (Storage Data) is packaged with three pH buffer packets required for calibration.

  • Open the pH7.00 buffer packet, place the powder into a 250ml volumetric flask. Pour distilled water 250ml to scale line, mix the solution until reagent is completely dissolved.
  • Preparation of pH4.01 and 10.01 standard buffer solutions are the same as above.
  • Prepared standard buffer solutions should be stored in hermetically sealed glass containers.

Refilling Electrolyte Solution for DO Probe

  1. Unscrew the membrane cap from the bottom of the dissolved oxygen probe.

  1. Fill the membrane cap halfway with electrolyte solution.

  1. Screw the membrane cap onto the probe, excess electrolyte will drain out.

  1. Be sure the cathode of probe makes contact with membrane cap, the electrolyte solution in membrane cap should be without an air bubble.

                   

Prior to Use

Remove the protective cap from the bottom of the sensor.

  • FOR THE pH ELECTRODE:

If the glass sensitive membrane on the electrode dries out, soak the electrode in 3 M KCl solution or tap water for at least 15 minutes. DO NOT use distilled or deionized water, it will shorten the life of sensor.

  • FOR THE ORP ELECTRODE:

Soak the electrode in 3 M KCl solution or tap water for 5 minutes.

  • FOR THE ION SELECTIVE ELECTRODES:

Soak the electrode in the diluted standard solution (e.g., 100 ppm) for at least 15 minutes.

  • FOR THE CONDUCTIVITY ELECTRODE:

Soak the electrode for a few minutes in tap water to remove dirt and oil stains on the electrode.

  • FOR THE DISSOLVED OXYGEN PROBE:

Connecting the probe to meter, turn on the meter 10 to 15 minutes and wait for the probe to polarize.

 Power On/Off

  • Press MEAS key to turn on the meter, the display shows measured values, mode indicators and help messages.
  • Press and hold the MEAS key for 3 seconds, the meter will turn off.
  • If you do not press any key within the specified time period, the meter will turn off automatically.

 Setup Menu

This PH Meter with Conductivity/TDS/Salinity (Storage Data) contains an integrated setup menu that allows you to customize each displayed option to meet measurement requirements. In the different modes, the meter will show the corresponding options. For the general options, once it is changed that will be applied to all modes.

pH MODE:

PARAMETER DESCRIPTION OPTIONS DESCRIPTION DEFAULT
      pH Buffers:

Select your desired pH buffer group for calibration and auto-recognition.

      USA (1.68, 4.01, 7.00, 10.01, 12.45)
NIST (1.68, 4.01, 6.96, 9.18, 12.45)
      DIN (1.09, 4.65, 6.79, 9.23, 12.75)
User-Defined Buffer
      Calibration Points:

Select the number of calibration points you intend to calibrate the meter.

           1 1 point
          2 2 points
         3 3 points
          4 4 points
          5 5 points
Resolution:

Sets the resolution for pH measurement.

0.001 0.001 pH
 0.01 0.01 pH
0.1 0.1 pH
Measurement Unit:

Sets the default temperature unit.

   Degrees Celsius
   Degrees Fahrenheit

ORP MODE:

PARAMETER DESCRIPTION OPTIONS DESCRIPTION DEFAULT
  Resolution:

Sets the resolution for ORP measurement.

        0.1 0.1 mV
         1 1 mV

ION MODE:

PARAMETER DESCRIPTION OPTIONS DESCRIPTION DEFAULT
Measurement Unit:

Sets the default ion concentration and temperature units.

ppm Parts per million
mg/L Milligrams per liter
mol/L Moles per liter
           Degrees Celsius
           Degrees Fahrenheit
  Calibration Points:

Select the number of calibration points.

        2 2 points
      3 3 points
         4 4 points
          5 5 points
       Ion Valence:

Select the ion valence of sensor.

    1 Monovalent
  2 Divalent

CONDUCTIVITY/TDS/SALINITY/RESISTIVITY MODES:

PARAMETER DESCRIPTION OPTIONS DESCRIPTION DEFAULT
  Cell Constant:

Select the cell constant of conductivity electrode.

    0.1 K=0.1
   1 K=1
        10 K=10
User-Defined
        Temperature Coefficient:

Select the temperature coefficient of sample.

   2.10 Setting Range: 0.0 to 10.0%/°C 2.10
      Calibration Points:

Select the number of calibration points.

       1 1 point
     2 2 points
       3 3 points
       4 4 points
      5 5 points
Pure Water Coefficient:

Pure water coefficient will be calculated and applied automatically for ultra-pure water measurement if enabled.

     YES Enable
     NO Disable
    Normalization Temperature:

Sets the normalization temperature for conductivity measurement and calibration.

      25 °C
    20 °C
      TDS Factor:

Sets the default TDS conversion factor.

      0.5 Setting Range: 0.40 to 1.00 0.5
   Measurement Unit:

Sets the default temperature unit.

     Degrees Celsius
     Degrees Fahrenheit

DISSOLVED OXYGEN MODE: 

PARAMETER DESCRIPTION OPTIONS DESCRIPTION DEFAULT
      Calibration Points:

Select the number of calibration points.

      1 1 point
      2 2 points
Pressure Coefficient:

Select the default atmospheric pressure coefficient.

     760 Setting Range: 450 mmHg to 850 mmHg 760
      Salinity Coefficient:

Select the salinity coefficient of sample solution.

        0.0 Setting Range: 0.0 ppt to 50.0 ppt 0.0
Resolution:

Sets the resolution for DO measurement.

    0.01 0.01 mg/L (0.1 %)
    0.1 0.1 mg/L (1 %)
Measurement Unit:

Sets the default measurement units.

        Degrees Celsius
        Degrees Fahrenheit
mg/L Milligrams per liter
ppm Parts per million
mmHg Pressure unit
kPa Pressure unit

GENERAL OPTIONS:

PARAMETER DESCRIPTION OPTIONS DESCRIPTION DEFAULT
    Stable Criteria:

Sets the stability criteria for measurement.

When the “LO” option is enabled, measuring value will stabilize quickly, but reading is less accurate.  When the “HI” option is enabled, measuring value will stabilize slowly, but guarantees high accuracy.

 LO Low
 HI High
Auto-Hold:

When the auto-hold function is enabled, the meter will automatically sense a stable end-point reading and freeze it.

  YES Enable
  NO Disable
OFF Auto-Power Off:

When the auto-off power is enabled, if you do not press any key within a specified time period, the meter will automatically turn off.

 10 10 minutes
 20 20 minutes
30 30 minutes
NO Disable
CALL Calibration Due:

When calibration due reminder is enabled, if you do not recalibrate meter within a specified time period, the meter will automatically show  indicator.

1 … 31 1 to 31 days
 OFF Disable
Date and Time:

Sets the date and time of the meter.

      Clear stored data:

Clear all stored data.

YES Enable
NO Disable
      Reset:

Reset function allows user to restore the meter back to factory default parameters. When this function is enabled, all calibration values and selected parameters will be lost or reset.

YES Enable
NO Disable

 pH Mode:

  • 1 to 5 points push-button calibration with auto-buffer recognition.
    Selectable pH buffer standard (USA/NIST/DIN) or using the custom calibration solutions.
  • Automatic electrode slope display helps user decide whether to replace sensor.

ORP Mode:

  • Single point offset calibration allows adjusting the displayed value to a known standard.
  • Relative and absolute millivolts measurement modes provide accurate ORP readings.

 Conductivity/TDS/Salinity/Resistivity Mode:

  • 1 to 5 points push-button calibration with automatic calibration solution recognition.
  • Selectable cell constant (0.1/1/10), normalization temperature (20/25°C), TDS conversion
    factor, seawater and practical salinity measurement modes.
  • Linear or pure water compensation improves measurement accuracy of meter.

Temperature Compensation

In order to get accurate measuring results, you need to enable the manual or automatic temperature compensation before measurement or calibration.

AUTOMATIC TEMPERATURE COMPENSATION:

  • Insert the connector of temperature probe into the meter’s phone jack.

  • The “ATC” indicator will show on the display, the meter is now switched to automatic temperature compensation mode.

Temperature Calibration

During the measurement, when automatic temperature compensation is enabled, if the temperature reading displayed differs from that of an accurate thermometer, you need to calibrate the meter.

  1. Press and hold the °C key for 3 seconds to enter temperature calibration mode, the display shows current temperature reading.

2. Press or  key to set the temperature value.

3. Press ENTER key to confirm. Calibration is completed.

pH Measurement

  1. Press MODE key until the meter shows   indicator.
  2. Rinse the pH electrode with distilled water to remove any impurities adhering to the probe body.
  3. Dip the electrode into the sample solution, stir the sensor gently.
  4. Wait for the reading to stabilize, record the measured value on the display.

ORP Measurement

This PH Meter with Conductivity/TDS/Salinity (Storage Data) contains two millivolt measurement modes.

ABSOLUTE MILLIVOLT MODE:

Press MODE key until the display shows measurement unit “mV”, the meter enters absolute millivolt measurement mode.

RELATIVE MILLIVOLT MODE:

Press MODE key until the display shows  indicator, the meter enters relative millivolt measurement mode.

Select one of the above modes. Dip the ORP electrode into sample solution, stir the sensor gently. Wait for reading to stabilize, record the measured value on the display.

Ion Concentration Measurement

  1. Press MODE key until the meter shows  indicator.
  2. Rinse the Ion Selective Electrode thoroughly with distilled water. Dip the electrode into the sample solution.
  3. If your sample belongs to low concentration liquids or some interfering ions are present in the solution, it is suggested that you add the Ionic Strength Adjuster into the sample solution.
  4. Stir the sensor gently. Wait for the reading to stabilize, record the measured value on the display.

Conductivity/TDS/Resistivity Measurement

  1. Press MODE key until the meter shows (conductivity) or (TDS) or  (Resistivity) indicator.

  1. Rinse the conductivity electrode thoroughly with distilled water.
  2. Dip the electrode into the sample solution, stir the sensor gently.
  3. Wait for the reading to stabilize, record the measured value on the display.

 Salinity Measurement

This meter provides two salinity measurement modes: practical salinity (unit: PSU) and natural seawater (unit: ppt).

  1. Press MODE key until display shows   indicator and measurement unit “PSU”, the meter now enters practical salinity measurement mode.
  1. If necessary, press MODE key again, the meter shows  indicator and mesurement unit “ppt”, the meter now enters seawater measurement mode.

  1. Select the desired measurement mode. Dip the electrode into sample solution. Stir the sensor gently.
  2. Wait for the reading to stabilize, record the measured value on the display.

 Dissolved Oxygen Measurement

This PH Meter with Conductivity/TDS/Salinity (Storage Data) is suitable for measuring the water, wastewater, brine and other liquids. If you use meter to measure seawater or other water containing large amounts of salt, please set the salinity coefficient before use.

Some gas and steam such as chloride, sulfur dioxide, sulfureted hydrogen, ammonium, carbon dioxide and iodine can permeate the membrane via diffusion. So their existence will influence the measurement of dissolved oxygen.

If the sample contains solvent, grease, sulfide and alga, the membrane on the probe will be blocked, damaged or eroded.

  1. Press MODE key until the meter shows indicator.
  2. Connecting the dissolved oxygen probe to meter, wait for 15 minutes to polarize the sensor.
  3. If necessary, to set the atmospheric pressure and salinity coefficient in the setup menu (Refer to “SETUP MENU” section).
  4. Submerse probe in the sample solution, make sure the temperature sensor on the probe is fully immersed.

  1. Stir the probe gently, wait for the reading to stabilize, record the measured value on the display.

 Hold Function

The meter contains two data hold modes

Storing and Recalling Data from Memory

This PH Meter with Conductivity/TDS/Salinity (Storage Data) allows up to 500 data sets to be stored and recalled.

Communication Software

This instrument comes with a free Data Acquisition System that can be used to transfer stored data, receive the measuring values or set the interval time for automatic recording. The system requirement is Windows XP or Windows 7.

RUNNING THE SOFTWARE:

Click the Data Acquisition System icon on the start bar, the DAS splash screen appears for few seconds and then the application starts.

RECEIVING THE STORED DATA:

Connect the USB cable to meter and computer (communication port: COM1, baud rate: 9600). Click the Receive button, the stored data in meter will automatically send to computer.

SEARCHING THE DATA:

If you would like to search a specific measured value from the database or uploaded data, click the Search button, the screen will show a Search Criteria dialog. Available search criteria include the time and sample name. After selecting or entering the search criteria, click the OK button, the screen will show all qualified records.

PRINT THE REPORT:

If you would like to print current data, click the Print button, the printer will output data sheet.

DATA RECALL:

DAS data acquisition system has a large database used to store the all uploaded data. If you need to view previous data, click the Recall button, the screen will show all data in the database.

DELETE THE DATA:

If you need to delete the certain data, click on the data field, then click the Delete button. Note: Once deleted, the data cannot be recovered.

GRAPH MODE:

The graph mode will help user to view variations of the measured parameter continuously. Click the Graph button, the screen will immediately show curve graph, measuring value and temperature.

INTERVAL MEASUREMENT AND AUTOMATIC RECORDING:

This function helps you automatically record the measuring value within the specify time period. Click the Interval Measurement button, the screen will show a dialog box. Selecting the time interval and recording time, click the OK button, the measured value will automatically transfer to data sheet.

CREATE THE EXCEL DATA FILE:

When the transfer is complete, click the “Import data into Excel” button, the measured value in the data sheet will be converted to Excel file. You can follow the path below to find the Excel file: C :> Program Files>Data Acquisition System>Excel

 NOTE:

The software runs in operating system Windows XP. If your system is Windows 7, please using the file “CP210x_VCP_Windows” to update your device manager.

If the computer displays “Error” during the first run, please open the windows “Run” command, then enter the command below in text input field:

regsvr32 “c:\windows\system32\DAO350.DLL

Please make sure your meter is connect to communication port “COM1”, baud rate: 9600.

pH Electrode Care and Maintenance

Since pH electrode is susceptible to dirt and contamination, clean as necessary depending on the extent and condition of use.

AFTER MEASURING: 

Rinse the pH electrode in distilled water, store the electrode into the electrode storage solution.

CLEANING THE ELECTRODE:

  • Salt deposits: Soak the electrode in warm tap water to dissolve deposits, then thoroughly rinse with distilled water.
  • Oil or Grease film: Wash the electrode bulb gently in some detergents and water. If necessary, using the alcohol to clean the electrode bulb, then rinse with distilled water. Place the sensor in the electrode storage solution for 30 minutes.
  • Clogged reference junction: Heat a diluted KCl solution to 140 °F to 176 °F (60 °C to 80 °C). Place the sensing part of the electrode into the heated solution for about 10 minutes. Allow the electrode to cool in some unheated KCl solution.
  • Protein deposits: Prepare a 1% pepsin solution in 0.1 M of HCL. Place the electrode in the solution for 10 minutes. Rinse the sensor with distilled water.

REACTIVATING THE ELECTRODE:

If stored and cleaned properly, the electrode should be ready for immediate use. However, a dehydrated bulb may cause sluggish response. To rehydrate the bulb, immerse the electrode in a pH 4.01 buffer solution for 10 to 30 minutes. If this fails, the electrode requires activation.

  • Soak the pH electrode in 0.1 M HCl for 5 minutes.
  • Remove and rinse with deionized water, then place in 0.1 M NaOH for 5 minutes.
  • Remove and rinse again, and soak in electrode storage solution for 30 minutes.

ORP Electrode Care and Maintenance

  • Ensure that the ORP electrode is thoroughly washed with distilled water after each use.
  • In aggressive chemicals, dirty or viscous solutions, and solutions with heavy metals or proteins, take readings quickly and rinse electrode immediately after.
  • If you do not use the electrode for long periods, please store the electrode with electrode storage solution.

CLEANING THE ELECTRODE:

Contamination of the sensing element often results in slow response and inaccurate readings. If necessary, clean the element by one of the following procedures.

Inorganic Deposits: 

  • Soak the ORP electrode in 0.1M HCl for 10 minutes.
  • Remove and rinse with distilled water, then place in alcohol for 5 minutes.
  • Remove and rinse again, and soak in pH4.01 buffer solution for 15 minutes.

Oil and Grease Films: 

  • Wash the electrode gently in some detergents and water.
  • Dip the electrode in the electrode storage solution for at least 30 minutes.

 Ion Selective Electrode Care and Maintenance

  • Ensure that the electrode is thoroughly washed with distilled water after each use.
  • DO NOT scratch the sensitive membrane on electrode during the measurement or calibration.
  • If you do not use the electrode for long periods, please store the electrode in a dry, cool and well-ventilated area.

Conductivity Electrode Care and Maintenance

  • Ensure that the conductivity electrode is thoroughly washed with distilled water after each use.
  • If there is a build-up of solids inside the measurement area of the cell, these should be removed very carefully with a cotton bud soaked in solvent, taking care not to touch the metal parts of the inner cell.

DO Probe Care and Maintenance

  • Please always keep probe’s membrane moist.
  • If you do not use the dissolved oxygen probe for long periods, please screw off membrane cap and rinse the probe’s cathode, anode and the membrane with deionized water, then soak up residual water on them with filter paper, and install the probe.

    

Troubleshooting

LCD DISPLAY CAUSE CORRECTIVE ACTION
Electrode dried out Soak the pH electrode in 3M KCL solution for 15 minutes
Soak the Ion Selective Electrode in the diluted standard solution
Soak the conductivity electrode in tap water for a few minutes
Measured value is out of range Check the electrode whether clogged, dirty or broken
Incorrect calibration solutions Using the fresh calibration solutions for calibration
Setting value does not match calibration solution Reset the calibration value
DO electrolyte solution is depleted Refilling electrolyte solution
Zero oxygen solution is contaminated Replace the calibration solution
pH electrode is out of service life Replace the pH electrode

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