GVDA PH818 Pen Type pH Meter

1. Introduction

The GVDA PH818 is an intelligent and precise measurement apparatus designed with high-sensitive components and sensors. It offers high accuracy and stable performance across different temperatures. Its compact size makes it easy to store and carry. This device measures pH values and the temperature of the solvent under test. The PH818 pH meter is widely used in industrial, electrical, agricultural, medical, and food industries. Please read this instruction manual thoroughly before use to ensure correct operation and accurate readings.

2. Product Overview

2.1 Explanation of Appearance

The diagram below illustrates the key components of your PH818 pH meter:

Figure 1: PH818 pH Meter Components

1. Power ON/OFF / and Hold button
2. Calibrate / increase button
3. Back light / reduce button
4. PH value reading area
5. Temperature reading area
6. PH Probe Electrode

2.2 LCD Display Screen

The LCD provides clear readings and indicators for various functions:

Figure 2: LCD Display Indicators

• Timer icon: Indicates auto power-off is active.
• Battery power indication: Shows remaining battery life.
• PH measured value: Displays the current pH reading.
• Data Hold icon (HOLD): Indicates that the current reading is frozen on the display.
• Calibration mode icon (CAL): Appears during calibration.
• Environmental temperature: Displays the ambient temperature.
• Measured value: Displays the temperature of the solution.
• Temperature unit °C/°F: Indicates the selected temperature unit.

3. Specifications

The technical parameters of the GVDA PH818 pH Meter are as follows:

4. Accessories

The standard package includes:

• Main unit: 1 pc (PH818 pH Meter)
• Calibration powder: 2 bags each of PH4.00, PH6.86, PH9.18 (for 250mL solution each)
• Instruction Manual and Warranty Card: 1 set

Figure 3: Package Contents

5. Setup & Calibration

5.1 Battery Installation

Open the battery door located at the top of the instrument. Insert two AAA size (1.5V) batteries into the compartment, ensuring correct polarity. Batteries are not included in the package.

Figure 4: Battery Installation

5.2 Calibration Procedure

If you have replaced the pH composite electrode or if the instrument has not been calibrated recently, perform calibration before use. If the measuring interval is short, monthly calibration is sufficient.

This unit uses a three-point calibration method. Follow these steps:

1. Ensure the unit and calibration solutions are at an ambient temperature of 25°C ±2°C.
2. In normal measurement mode, press and hold the [CAL/▲] key for more than 3 seconds to enter Calibration Mode 1.
3. The LCD screen will flash “CAL1” and display “4.00”. Rinse the pH electrode with distilled water. Immerse the electrode in the PH4.00 buffer solution. Once the instrument detects a stable signal, the LCD will show “PAS”, indicating successful PH4.00 calibration. The unit will then automatically proceed to CAL 2 mode, with “CAL2” flashing and “6.86” displayed.
4. Clean the sensor electrode quickly with distilled water. Immerse the electrode in the PH6.86 buffer solution. Once stable, the LCD will show “PAS”, indicating successful PH6.86 calibration. The unit will then automatically proceed to CAL 3 mode, with “CAL3” flashing and “9.18” displayed.
5. Clean the sensor electrode quickly with distilled water. Immerse the electrode in the PH9.18 buffer solution. Once stable, the LCD will show “PAS”, indicating successful PH9.18 calibration. The unit will then return to normal measurement mode.
6. If the pH value displayed during calibration does not match the default value, you can adjust the value using the [CAL/▲] or [▼] keys to match your calibration buffer solution, then proceed with the calibration procedure as mentioned above.

Appendix: Preparation of Buffer Solution

• PH4.00 buffer solution: Dissolve the PH4.00 powder in 250mL distilled water. Mix carefully until fully dissolved. Let it stand for 30 minutes.
• PH6.86 buffer solution: Dissolve the PH6.86 powder in 250mL distilled water. Mix carefully until fully dissolved. Let it stand for 30 minutes.
• PH9.18 buffer solution: Dissolve the PH9.18 powder in 250mL distilled water. Mix carefully until fully dissolved. Let it stand for 30 minutes.

6. Operation

6.1 Normal Measure Mode

The factory default mode is normal measuring mode. To turn on the unit, press the [ON/OFF/HOLD] button. The unit will enter normal measure mode, allowing it to measure pH and environmental temperature simultaneously. Simply immerse the electrode into the solution you wish to measure.

6.2 Button Functions

• [ON/OFF/HOLD] key:
  • Press once to turn the unit on.
  • After turning on, press once to hold the measured pH value data.
  • Press and hold for more than 3 seconds to turn it off.
• [CAL/▲] Key:
  • In normal measurement mode, press and hold for more than 3 seconds to enter Calibration mode.
  • In CAL mode, press to increase the value. Press and hold for more than 3 seconds to increase the value more quickly.
• [▼] Key:
  • In normal measurement mode, press to turn the backlight on or off.
  • In CAL mode, press to reduce the pH value. Press and hold for more than 3 seconds to reduce the value more quickly.

6.3 Auto or Manual Power Off Setup

Before turning on the unit, press and hold the [ON/OFF/HOLD] key and [CAL/▲] key simultaneously. The unit will enter “Auto power off” mode setup screen, displaying “APO ON” or “APO OFF”. Press the [ON/OFF/HOLD] key to select “APO ON” or “APO OFF” sequentially. Once your selection is made, press and hold the [ON/OFF/HOLD] key for more than 3 seconds to save the setting and return to normal measurement mode.

• APO ON mode: The LCD screen will show the timer icon. If no key is detected for 15 minutes, the unit will automatically power off.
• APO OFF mode: The LCD screen will not show the timer icon. You must manually turn off the unit by pressing and holding the [ON/OFF/HOLD] key.

6.4 Temperature Unit Selection (°C/°F)

Before turning on the unit, press and hold the [ON/OFF/HOLD] key and [▼] key simultaneously. The unit will enter temperature unit selection mode, displaying “°C” or “°F”. Press the [ON/OFF/HOLD] key to select “°C” or “°F” sequentially. After selection, press and hold the [ON/OFF/HOLD] key for more than 3 seconds to save the setting and return to normal measurement mode.

7. Maintenance & Care

7.1 Re-calibration Circumstances

The instrument must be re-calibrated under the following circumstances:

• The solution temperature has a large difference from the calibrated temperature.
• The pH electrode has been out of the liquid storage bottle for too long.
• The pH electrode has been replaced with a new one.
• After measuring highly concentrated acid (PH<2) or alkali (PH>12) solutions.
• After measuring fluoride solution and acidity within PH<7 or concentrated organic solutions.
• When calibrating, ensure the buffer solution temperature is 25°C ±2°C.

7.2 Instrument Maintenance

Proper maintenance is crucial for the performance and longevity of your pH meter, especially given its exposure to acidic or alkaline chemical environments.

1. The input port (pH composite electrode) must be kept in good condition: dry, clean, and do not remove the plug from the unit unless for long-term storage.
2. The head of the pH composite electrode is delicate. Avoid touching it with hard objects to prevent damage.
3. Do not allow dirt to contact the head of the composite electrode. If it becomes dirty, clean it with medical soft cotton or a 0.1mol/L dilute hydrochloric acid solution.
4. If the pH composite electrode cracks or ages (e.g., after more than one year in stock), it must be replaced. A damaged electrode will cause slow response or significant measurement errors. Before using a new electrode, immerse it in 3 mol/L potassium chloride solution for 24 hours.
5. The accuracy and reliability of the buffer solution are critical for calibration. If the buffer solution is inaccurate, it will lead to significant measurement errors. Refer to the Appendix for buffer solution preparation.

7.3 Special Care

1. Before use, it is highly recommended to calibrate the instrument with a precise and reliable buffer solution, especially if the pH value is close to the object solution.
2. After removing the protection bottle, avoid touching the glass bulb and hard objects, as it is very fragile. Any scratch or crack will cause malfunction.
3. After use, place the protection bottle back on. Ensure the bottle contains enough de-ionized water or rinse solution (tap water) before the next use.
4. The buffer solution for the reference and compare electrode is 3.3mol/L Potassium chloride solution. Users can refill it into the small hole on top of the composite electrode, which is sealed with a silicone rubber tag.
5. The contact pin of the electrode must be kept dry and clean. Do not short-circuit the pin, as this will damage the electrode.
6. Avoid immersing the pH composite electrode into distilled water, protein solution, Fluorine chemicals acid solution, and contact with silicone grease.
7. If the pH composite electrode's sensitivity decreases after prolonged use, immerse the head side of the electrode in a 4% HF solution (Hydrofluoric acid) for 3-5 seconds. Then clean with distilled water and immerse in Potassium chloride solution to recover it.
8. If the measured solution dirties the glass bulb or blocks its surface, clean the electrode with a suitable solvent to restore sensitivity. Be cautious when selecting cleaning solvents; some solvents (e.g., Carbon tetrachloride, Trichloroethylene, Tetrachlorofuran) can dissolve polycarbonate resin and damage the glass bulb.

Warm Reminder (Figure 5: Probe Immersion)

Figure 5: Probe Immersion Warning

During instrument calibration, do not immerse the probe head below the marked level to prevent water from entering the instrument and causing short circuits.

8. Troubleshooting

• Low Battery Indication: If the battery power indicator icon on the top right-hand side becomes empty, replace the two AAA batteries immediately. If the instrument will not be used for a long period, remove the batteries from the compartment to prevent leakage.
• Over Range Alert:
  • If the measured pH value is lower than 3.5pH, the red backlight will turn on, indicating a strong acid.
  • If the measured pH value is higher than 12.5pH, the red backlight will turn on, indicating a strong alkali.
• Temperature Display Issues:
  • If the environment temperature is below 0°C, the LCD screen will show “LO”.
  • If the environment temperature is higher than 70°C, the LCD screen will show “Hi”.
• Inaccurate Readings or Slow Response: This can be caused by a dirty, cracked, or aged electrode, or inaccurate buffer solutions. Refer to the 'Maintenance & Care' section for cleaning and replacement procedures, and ensure buffer solutions are prepared correctly.

9. User Tips

• Regular Cleaning: Always rinse the electrode with distilled water before and after each use to maintain accuracy and prolong its lifespan.
• Proper Storage: Store the pH meter with its protective cap on, ensuring the cap contains de-ionized water or rinse solution to keep the electrode moist.
• Battery Management: Remove batteries if the device will not be used for an extended period to prevent potential damage from leakage.
• Environmental Consistency: For best results, perform calibration and measurements in a stable environment, avoiding extreme temperature fluctuations.

10. Frequently Asked Questions (FAQ)

Q: How often should I calibrate my pH meter?

A: If used frequently, monthly calibration is recommended. Re-calibrate immediately if the solution temperature differs significantly from the calibration temperature, after replacing the electrode, or after measuring highly concentrated solutions.

Q: What kind of batteries does the PH818 use?

A: It uses two 1.5V AAA batteries (not included).

Q: Can I use tap water for electrode storage?

A: Yes, tap water or de-ionized water can be used in the protective cap for short-term storage. Avoid distilled water for long-term storage as it can deplete the electrode's internal electrolyte.

Q: What should I do if the display shows 'LO' or 'Hi' for temperature?

A: 'LO' indicates the temperature is below 0°C, and 'Hi' indicates it's above 70°C. The meter operates within 0-50°C, so these readings are outside the optimal working range.

11. Warranty & Support

Please refer to the included Warranty Card for detailed information regarding your product's warranty period and terms. For further technical support or inquiries, please contact your retailer or the manufacturer directly.

A digital version of the user manual (PDF) can be found here: View User Manual (PDF).

Our company reserves the right to change the design and the user manual without prior notice to the end user.