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Overview

GAOTek PH Meter with ORP/Temp (High Precision, 5 Point Calib) is designed using 5 point calibration for high accuracy measurements and supports automatic temperature compensation over the entire pH range from -2.000 pH ~ 20.000 pH. This portable device features auto and manual power off function, calibration due reminder etc. Automatic electrode slope display helps you decide whether to replace sensor. The device is equipped with a huge backlit LCD display.

Key Features

  • System menu allows setting the 9 parameters, including the pH buffer standard, number of calibration points, resolution, stability condition, temperature unit, etc.
  • Automatic electrode diagnosis shows zero point offset and slope of the pH electrode.
  • Manual temperature calibration improves the measurement accuracy of meter.
  • Reset feature automatically resumes all parameters back to factory default settings.
  • Stability indicator automatically shows current measurement status.
  • Stored data can be transferred into computer by USB communication interface.
  • Expanded memory stores and recalls up to 500 readings.
  • Selectable temperature unit (°C or °F) meets different application requirements.
  • Built-in real-time clock stamps stored data to meet GLP standard.
  • Auto-Hold function freezes stable measured value for easy viewing and recording.
  • Help message as an operational guide that helps you quickly begin using the meter.

Technical Specifications

pH
Range -2.000 pH ~ 20.000 pH
Resolution 0.1 pH, 0.01 pH, 0.001 pH, Selectable
Accuracy ±0.002 pH
Calibration Solutions USA, NIST, DIN or User-defined
Calibration Points 1 to 5 points
Compensation Mode Manual or Automatic
Temperature Compensation 32 °F~212 °F (0 °C~100 °C)
mV
Range -1999.9 mV~1999.9 mV
Resolution 0.1 mV, 1 mV, Selectable
Accuracy ±0.2 mV
Calibration Range ±200 mV
Calibration Points 1 point (Only for Relative mV mode)
Temperature
Range 32 °F~221 °F (0 °C~105 °C)
Resolution 32.18 °F (0.1 °C)
Accuracy ±0.9 °F, ±0.5 °C
Temperature Units °F or °C
Calibration Range Measured value ±50 °F (±10 °C)
Others
Calibration Due 0 to 31 days
Reset Function Yes
Stability Conditions Low or High
Hold Function Manual or Automatic
Output USB Communication Interface
Display LCD 5.11 in×4.33 in (130 mm×110 mm)
Power Requirements DC 5V, using AC adapter, 220 VAC/50 Hz
Memory Stores up to 500 data sets
Power Off Manual or Automatic (10, 20, 30 minutes)
Connector BNC
Dimensions 8.26 (L) in×7.40 (W) in×2.36 (H) in (210 (L) mm×188 (W) mm×60 (H) mm)
Weight 3.30 lbs (1.5 kg)

Additional Information

pH Mode:
• High precision benchtop pH meter is equipped with a large backlit LCD display.
• 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.
• Automatic Temperature Compensation provides accurate reading over the entire pH range.
• Calibration Due Reminder prompts you to calibrate the meter regularly.

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.

ACCESSORIES:

  • pH Electrode
  • Temperature Probe
  • pH Buffer Pouches (pH4.01/7.00/10.01)
  • USB Cable
  • DC5V Power Adapter

Display

The device 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.

INDEX:

Measurement mode indicator: Indicates meter is in the measurement mode Electrode slope indicator: Indicates the average slope of the pH electrode
Calibration mode indicator: Indicates meter is in the calibration mode Stable indicator: Indicates the measured value has stabilized
Setup mode indicator: Indicates meter is in SETUP mode Hold indicator: Indicates the displayed value has been frozen
Memory mode indicator: Indicates data is stored into memory Calibration Due Reminder: Prompts user to calibrate the meter regularly

Keypad

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

MEAS|

  • Power the meter ON/OFF.
  • Freezes the measured value on the display, press the key again to resume measuring.
  • In the calibration or temperature setting mode, exits current mode and returns to measurement.

MODE|oC

  • Toggles between available measurement 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 values.

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 values.

ENTER

  • Confirms the calibration, setting value or displayed option.
  • Press and hold the key to turn On/Off the backlight.

Connectors

The pH meter provides 4 connectors for connecting the various types of sensors. Listed in the below table are the details of these connectors.

INDEX:

NO. CONNECTOR FUNCTION
1 pH/ISE For connecting the pH or ORP electrode
2 ATC For connecting the temperature probe
3 REF For connecting the reference electrode
4 USB/ For connecting the USB cable and DC5V power adapter

Connecting the Electrode Holder

The meter comes with an easy-to-use holder for mounting a variety of sensors and temperature probe. If necessary, please follow the steps below to install the electrode holder.

  1. The base of the electrode holder with an irregular round hole.

  1. The electrode arm has a plastic rod.

  1. Insert the plastic rod into the irregular round hole and swivel the electrode arm 90°. Electrode holder is now ready to swing into desired position.

ADJUSTMENT OF ELECTRODE ARM:

After installation, if the electrode arm automatically rises or falls, you need to adjust the screws until arm locate at any position.

  1. Remove the plastic cover from the electrode arm.

2.Use the screwdriver to tighten the screw moderately.

  1. Insert the plastic cover to previous position. Installation is completed.

Connecting the Electrode

  1. Take out the pH or ORP electrode from the packaging. Follow the steps below to place the electrode into left or right sides of the electrode arm.

  1. Insert the BNC connector into the 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

The device is packaged with three pH buffer packets required for calibration.

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

Prior to Use

Remove the protective cap from the bottom of the electrode.

FOR THE pH ELECTRODE:

If the glass sensitive membrane on the electrode dries out, soak the sensor in 3M 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 4M KCL solution or tap water for at least 15 minutes.

Power On/Off

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

Setup Menu

The device 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:

ORP MODE:

Setting the Default Parameters

  1. If necessary, press MODE key until the display shows corresponding mode indicator (e.g., pH mode).

  1. Press and hold the key for 3 seconds, the meter enters setup menu, the display shows selectable parameter and page number.

  1. Press ▼or ▲ key to scroll through menu, select the parameter you want to set.

  1. Press ENTER key to confirm, the display shows an option in the submenu.

  1. Press ▼ or ▲ key to select the desired option.
  2. Press ENTER key to confirm, the meter returns to measurement mode. Setting is completed.

EXIT THE SETUP MENU:

During the setup mode, press MEAS key, the meter returns to measurement mode immediately.

Setting the Date and Time

The device has a real time clock that is used to time-stamp stored measured value and calibration data. Follow the steps below to set the date and time during the first use.

  1. Press and hold the key for 3 seconds to enter the setup menu.
  2. Press ▲ or ▼ key until the display shows “DATE” option.

  1. Press ENTER key to confirm, the meter shows current year.
  2. Press ▼or ▲ key to set the year.
  3. Press ENTER key to confirm, the meter shows current date and time.
  4. Press ▲ or ▼ key to set the date and time.
  5. Press ENTER key to confirm, the meter returns to measurement mode. Setting is completed.

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:

  • Place the temperature probe into the circular hole of electrode arm.

  • Insert the connector of temperature probe into corresponding connector socket (Marked “ATC”).

  • The “ATC” indicator will be shown on the display; 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 ▼ key or ▲ key to set the temperature value of sample.
  4. Press ENTER key to confirm, the meter returns to measurement mode. Setting is completed.

pH Calibration

The pH meter allows up to 5 points calibration in the pH mode. 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 pH1.68, 4.01, 7.00, 10.01, 12.45
NIST Standard Buffer Options pH1.68, 4.01, 6.86, 9.18, 12.45
DIN Standard Buffer Options pH1.09, 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 pH7.00, 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:

1.1Make sure that you have selected 1 point calibration in the setup menu.

1.2Rinse the pH electrode with distilled water.

1.3Press CAL key, the meter shows “pH7.00/CAL” (or “6.86/CAL”, “6.79/CAL”).

1.4Dip 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.

1.5Press 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:

2.1 Make sure that you have selected 2 to 5 points calibration in the setup menu.

2.2 Repeat steps 1.2 to 1.5 above. When the first calibration point is completed, the display will show “CAL2”. The meter prompts you to continue with second point calibration.

2.3 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.

2.4 Wait for the measured value to stabilize, the display shows “CAL3”. The meter prompts you to continue with third point calibration.

2.5 Repeat the steps 2.3 until the display shows “END”. The meter returns to measurement mode automatically. Calibration is completed.

pH CALIBRATION WITH THE USER-DEFINED BUFFERS:

3.1 Make sure that you have selected “USER” option in the setup menu. Custom buffer solution values should be at least 1 pH unit apart from each other.

3.2 Rinse the pH electrode with distilled water. Dip the electrode into the custom buffer solution. Stir the sensor gently. The meter shows the current measured value.

3.3 Press ▲ or ▼ key to increase or decrease displayed value, press ENTER key to confirm. “Calibration” indicator begins flashing.

3.4 Wait for the measured value to stabilize, the display shows “CAL2”. The meter prompts you to continue with second point calibration.

3.5 Rinse the pH electrode with distilled water. Dip the electrode into the next custom buffer solution.

3.6 Press ▲ or ▼ key to increase or decrease displayed value, press ENTER key to confirm. “Calibration” indicator begins flashing.

3.7 Wait for the measured value to stabilize, the display shows “END”. The meter automatically returns to measurement mode. 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).

  1. Press ENTER key to confirm, the meter shows the last calibration date (Format: mm-dd).
  2. Press ▼ key, the meter shows “OFS” (zero-point offset potential
  3. Press ▼ key again, the meter shows the slope of each pH buffer group.
  4. After the browsing, press MEAS key to exit the current mode.

ORP Calibration

The pH meter 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.

  1. Press ▲ or ▼ key to set the displayed value, press ENTER key to confirm. “Calibration” indicator begins flashing.

  1. 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).
  1. Press ENTER key to confirm, the meter shows the last calibration date (Format: mm-dd).

  1. Press ▼ key, the meter shows “OFS” (Offset Potential).

  1. 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 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

The pH meter contains two millivolt measurement modes.

ABSOLUTE MILLIVOLT MODE:

  • Press MODE key until the display shows measurement unit “mV”, the meter is now 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 the 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 key, the meter will immediately freeze currently displayed value.

Press the key again to resume measuring.

Storing and Recalling Data from Memory

The device 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).

  1. Press ENTER key to confirm, the meter shows page number of the stored data.
  2. Press ▼ key, the meter shows date and time of the stored data (Format: mm-dd, hh-mm).

  1. Press ▼ key again, the display shows the stored data.

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

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, use 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 °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 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 pH4.01 buffer solution for 10 to 30 minutes. If this fails, the electrode requires activation.

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

ORP Electrode Care and Maintenance

  1. Ensure that the ORP electrode is thoroughly washed with distilled water after each use.
  2. In aggressive chemicals, dirty or viscous solutions, and solutions with heavy metals or proteins, take readings quickly and rinse electrode immediately after.
  3. 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:

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

Oil and Grease Films:

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

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