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Overview

GAOTek PH Meter with 5 Points Calibration (High Accuracy) is designed in the accuracy of 0.002 pH and supports relative and absolute millivolts measurement modes. This pH meter provides automatic temperature compensation which gives accurate reading over the entire pH range. It is equipped with a large backlit LCD screen. The pH mode provides 1 to 5 points push button calibration with auto buffer recognition. The built-in real time clock stamps stored data to meet GLP standard. It offers multimode power scheme which allows the portable pH meter to work smoothly.

Key Features

  • Clear and bright LCD display used to display measured values, mode indicators and help message.
  • Stability indicator automatically display current measurement status.
  • Multi-mode power scheme (battery, power adapter, computer’s USB port) ensures that use the meter smoothly.
  • 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 improves the measurement accuracy of meter.
  • Automatic electrode diagnosis shows zero point offset and slope of the pH electrode.
  • System menu allows setting the 9 parameters, including the pH buffer standard, number of calibration points, resolution, stability condition, temperature 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
  • Reset feature automatically resumes all parameters back to factory default settings.

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 32 ˚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)
Temperature
Range 32 ˚F ~ 221 ˚F (0 ˚C ~ 105 ˚C)
Accuracy ± 0.5 °C, ± 0.9 °F
Resolution 32.18 °F (0.1 °C)
Temperature Units °C or °F
Calibration Range ± 10 °C measured value
General Specification
Interface USB communication interface
Connector BNC
Memory Up to 500 sets
Calibration Due 0 to 31 days
HOLD Function Manual or Automatic
Stability Conditions Low or High
Reset Function Yes
Power Requirements 3 x 1.5 V “AA” batteries
Battery Life 150 hours (approximately) (Turn off the backlit)
Dimensions 6.69 in × 3.35 in × 1.18 in (170 mm × 85 mm × 30 mm)
Weight 10.58 oz. (300 g)

Additional Information

ACCESSORIES:

  • pH Electrode
  • Temperature Probe
  • pH Buffer Pouches (pH 4.01, 7.00, 10.01)
  • AA batteries

Display

PH Meter with 5 Points Calibration (High Accuracy) is equipped with a clear and bright LCD display that used to show measured values, mode indicators and help message. The following table describes the meaning of each indicator.

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).

· 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 5 Points Calibration (High Accuracy) provides 2 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, or ORP Electrodes
2 Phone Jack For connecting the temperature probe

Inserting the Batteries

Before using the meter, insert three 1.5V “AA” alkaline batteries into battery compartment, follow the procedure outlined below.

  1. Remove the battery cover from meter’s backside.
  2. Insert the batteries into the battery compartment, note polarity.
  3. Replace the battery cover into its original position. Installation is completed.

When batteries are depleted, the meter allows you to use the USB cable connected to computer as a temporarily power supply.

Connecting the Electrode

Take out the pH or ORP electrode from the carrying case. Insert the BNC connector into corresponding connector socket. Rotate and push the connector clockwise until it locks. 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 5 Points Calibration (High Accuracy) 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.

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 4 M KCl solution or tap water for 15 minutes.

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

PH Meter with 5 Points Calibration (High Accuracy) 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

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

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

MANUAL TEMPERATURE COMPENSATION:

  1. DO NOT connect the temperature probe to meter.
  2. Press and hold the °C key for 3 seconds to enter temperature setting mode.
  3. Press ▲or ▼ key to set the temperature value of sample.
  4. Press ENTER key to confirm, the meter returns to measurement mode. Setting is completed.

In the temperature setting mode, press ▲or ▼key once, the setting value will increase or decrease by 0.1. Press and hold the ▲or ▼key, the setting value will increase or decrease by 1

pH Calibration

This PH Meter with 5 Points Calibration (High Accuracy) allows up to 5 points calibration in the pH mode. It is recommended that you perform at least 2 points calibration for high accuracy measurement. The meter will automatically recognize and calibrate to following standard buffer values.

USA Standard Buffer Options pH 1.68, 4.01, 7.00, 10.01, 12.45
NIST Standard Buffer Options pH 1.68, 4.01, 6.86, 9.18, 12.45
DIN Standard Buffer Options pH 1.09, 4.65, 6.79, 9.23, 12.75

If you selected the user-defined option in the setup menu, the meter will allow only 2 points calibration. Single point calibration should only be carried out with pH 7.00, 6.86 or 6.79, otherwise calibration will not be accepted.

Make sure to calibrate the meter when attaching a new electrode or during first use. DO NOT reuse calibration solution after calibration, contaminants in solution will affect the calibration and eventually the accuracy of the measurement.

SINGLE POINT CALIBRATION:

  • Make sure that you have selected 1 point calibration in the setup menu.
  • Rinse the pH electrode with distilled water.
  • Press CAL key, the meter shows “pH7.00/CAL” (or “6.86/CAL”, “6.79/CAL”).

  • Dip the pH electrode into the pH7.00 (or 6.86, or 6.79) buffer solution, the end of the electrode must be completely immersed into the calibration solution. Stir the sensor gently to create a homogenous solution.
  • Press ENTER key, “Calibration” indicator begins flashing. Wait for the measured value to stabilize, the display shows “END”. The meter returns to measurement mode automatically. Calibration is completed.

MULTI-POINT CALIBRATION:

  • Make sure that you have selected 2 to 5 points calibration in the setup menu.
  • Repeat above steps. When the first calibration point is completed, the display will show “CAL2”. The meter prompts you to continue with second point calibration.

  • Rinse the pH electrode with distilled water. Dip the electrode into the next standard buffer solution (e.g., pH4.01). The meter automatically senses the current calibration solution and begins calibrating. “Calibration” indicator begins flashing.

  • Wait for the measured value to stabilize, the display shows “CAL3”. The meter prompts you to continue with third point calibration.
  • Repeat the steps until the display shows “END”. The meter returns to measurement mode automatically. Calibration is completed.

pH Calibration Report

This program lets you check the parameters of pH electrode for diagnostic purposes.

  1. Press MR key in the pH measurement mode, the display shows “LOC/P-01”.
  2. Press▲or ▼key until the meter shows “ELE/P-02” (Electrode Diagnosis).
  3. Press ENTER key to confirm, the meter shows the last calibration date (Format: mm-dd).

  1. Press▼ key, the meter shows “OFS” (zero-point offset potential).
  2. Press▼ key again, the meter shows the slope of each pH buffer group.

  1. After the browsing, press MEAS key to exit the current mode.

If you did not calibrate the meter or calibration is not successful, press MR key, the display will show “—-” only.

ORP Calibration

PH Meter with 5 Points Calibration (High Accuracy) allows 1 point calibration in the relative mV mode, but calibration is not necessary unless exact readout agreement with a work standard and at a specific ORP value is needed.

  1. Press MODE key until the meter shows indicator.
  2. Rinse the ORP electrode with distilled water. Dip the electrode into the calibration solution. Stir the sensor gently.
  3. Press CAL key, the meter shows the current measured value.
  4. Press ▲ or ▼ key to set the displayed value, press ENTER key to confirm. “Calibration” indicator begins flashing.
  5. Wait for the measured value to stabilize, the display shows “END”. The meter returns measurement mode automatically. Calibration is completed.

ORP Calibration Report

This program lets you check the millivolt offset in the ORP mode.

  1. Press MR key in the ORP measurement mode, the display shows “LOC/P-01”.
  2. Press ▲ or ▼key until the meter shows “ELE/P-02” (Electrode Diagnosis).
  3. Press ENTER key to confirm, the meter shows the last calibration date (Format: mm-dd).
  4. Press ▼key, the meter shows “OFS” (Offset Potential).
  5. After the browsing, press MEAS key, the meter returns to measurement 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 showsindicator
  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 5 Points Calibration (High Accuracy) 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.

Hold Function

The meter contains two data hold modes. When the Auto-Hold function is enabled, the meter will automatically sense a stable endpoint reading and freeze it, “HOLD” indicator appears on the display. If the Auto-Hold function is disabled, press the key, the meter will immediately freeze currently displayed value. Press the key again to resume measuring.

Storing and Recalling Data from Memory

PH Meter with 5 Points Calibration (High Accuracy) allows up to 500 data sets to be stored and recalled.

MEMORY INPUT:

During the measurement process, press MI key to input measured value into the memory, “Memory” indicator appears on the display.

MEMORY RECALL:

  1. Press MR key in the measurement mode, the meter shows “LOC/P-01” (Data Log).
  2. Press ENTER key to confirm, the meter shows page number of the stored data.

  1. Press ▼key, the meter shows date and time of the stored data (Format: mm-dd, hh-mm).
  2. Press ▼ key again, the display shows the stored data.
  3. After the browsing, press MEAS key to exit the current mode.

Communication

GAOTek Instruments provides a free Data Acquisition System that can be used to transfer data, receive the measuring values or import the data to Excel. Before using, ensure that Windows 7/8/10 operating system has been installed on your computer.

RECEIVING DATA:

  • Connect the USB cable to meter and computer. Click the DAS icon, the system will automatically scan an available communication port and show the message box “Found a port on your computer”.
  • Click the OK button, the application starts.
  • Click the Connect button, the screen shows “Port is connected” indicate that communication between the meter and the computer has been established.
  • Click the OK button to confirm.
  • Click the Receive button, the stored data in meter will automatically send to computer.

INTERVAL RECORDING:

This function helps you to record the measuring value within the specify time period.

  • Click the Interval Recording button and select a time option.
  • Click the Receive button, the measured value will automatically send to data sheet.
  • The first data need 1 minute to be shown on screen.
  • Do not press any key on meter during the Interval Recording mode, it will cause communication interruption

GRAPH MODE:

This function helps you to view variations of the measured parameter continuously. Click the Graph button, the screen will immediately show curve graph. If you want to quit current mode, click the Back button.

CREATE THE EXCEL FILE:

When the transfer is completed, click the “Save as Excel” button, the measured values in the data sheet will automatically convert to Excel file.

WARNING:

Once the software is closed, all received data will be lost and cannot be recovered.

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 60 oC to 80oC. 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 0.1M 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 pH4.01 buffer solution for 10 to 30 minutes. If this fails, the electrode requires activation.

  • Soak the pH electrode in 0.1M HCl for 5 minutes.
  • Remove and rinse with deionized water, then place in 0.1M 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.

HOW TO PREPARE THE ELECTRODE STORAGE SOLUTION:

Dissolve 22.365 grams of potassium chloride reagent (KCL) in the 100mL distilled water. Stir the solution until the solution has thoroughly mixed.

Optional pH Electrodes

The instrument is equipped with a general purpose pH electrode, if it cannot fully meet your measurement requirements, please refer to the table below to select an applicable sensor.

SAMPLE TYPE P11 P12 P13 P14 P16 P17 P18 P19 P20 P21
Agar
Beer
Blood Products
Bread, Dough
Cement
Cosmetics
Dairy Products
Education
Fats/Cream
Field Use
Fish Products
Lab Flasks
Low Ionic
Meat, Cheese
Micro Samples
Paint
Photographic
Soil
Surface
Test Tubes
Tris Buffer
Viscose Samples

Troubleshooting

LCD DISPLAY CAUSE CORRECTIVE ACTION
Electrode dried out Soak the pH electrode in 3M KCL solution for 10 minutes
Measured value is out of range Check the electrode whether clogged, dirty or broken
Incorrect pH buffer solutions Using the pH buffer solutions for calibration
electrode is out of service life Replace the pH electrode
Keypad is not working properly Replace the batteries

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