Hanna GroLine Waterproof EC/TDS (PPM) Tester HI98318

 

The Hanna GroLine HI98318 Waterproof EC/TDS Tester provides a fast, convenient way to measure fertilizer concentration in hydroponic nutrient solutions. Its pocket-sized design, large dual-level display, selectable PPM scales, and automatic temperature compensation make it an excellent everyday meter for hydroponic gardens, greenhouses, aquaponic systems, and indoor growing environments.

The HI98318 displays EC or TDS alongside solution temperature, allowing growers to quickly determine whether a reservoir is within the desired nutrient-strength range. Its graphite conductivity sensor helps reduce the polarization effects commonly associated with conventional two-pin metal testers.

Key Benefits

• Measures electrical conductivity in mS/cm
• Displays TDS using selectable 500 or 700 PPM scales
• Displays nutrient-solution temperature
• Waterproof housing designed for humid growing environments
• Graphite conductivity sensor reduces polarization effects
• Automatic temperature compensation
• Large, easy-to-read dual-level LCD
• Simple two-button operation
• Automatic single-point calibration
• Compatible with Hanna Quick Calibration Solution
• Stability, calibration, and low-battery indicators
• Selectable automatic shutoff
• Approximately 250 hours of continuous battery life

Measurement Specifications

Parameter	Range	Resolution	Accuracy
EC	0.00 to 6.00 mS/cm	0.01 mS/cm	±2% full scale
TDS, 0.5 factor	0 to 3000 ppm	10 ppm	±2% full scale
TDS, 0.7 factor	0 to 4000 ppm	10 ppm	±2% full scale
Temperature	0.0 to 50.0°C / 32.0 to 122.0°F	0.1°C / 0.1°F	±0.5°C / ±1°F

Understanding EC and TDS

Electrical conductivity measures how effectively a solution conducts electricity. As dissolved fertilizer salts increase, conductivity generally increases. This makes EC a useful measurement for monitoring the overall concentration of a hydroponic nutrient solution.

TDS or PPM is calculated from the EC measurement using a conversion factor. Because different fertilizer manufacturers use different conversion scales, the HI98318 allows the user to select either:

• 0.5 or 500 PPM scale: An EC value of 1.00 mS/cm is displayed as approximately 500 ppm.
• 0.7 or 700 PPM scale: An EC value of 1.00 mS/cm is displayed as approximately 700 ppm.
• Direct EC display: Results are shown in mS/cm without conversion to PPM.

Always confirm which conversion scale is used by your nutrient manufacturer before comparing the meter’s PPM reading with a feeding chart.

Graphite Conductivity Sensor

The HI98318 uses a graphite conductivity sensor that helps minimize polarization effects. Polarization can occur with conventional two-pin metal testers and may contribute to unstable or less repeatable measurements.

The graphite sensor provides dependable conductivity readings while standing up to regular use in fertilizer-rich hydroponic solutions.

Automatic Temperature Compensation

Conductivity changes as solution temperature changes. The HI98318 automatically compensates EC and TDS readings between 0 and 50°C, helping growers compare nutrient-strength measurements taken under different reservoir conditions.

The integrated temperature sensor also displays the measured temperature on the secondary portion of the LCD.

Calibration Options

The HI98318 offers automatic single-point calibration using either:

• 1.41 mS/cm conductivity standard in standard calibration mode
• Hanna Quick Calibration Solution at 5.00 mS/cm in Quick Cal mode

The meter automatically recognizes the appropriate calibration standard and stores the calibration after the reading stabilizes.

For dependable results, Hanna recommends calibrating at least once per month and more frequently when high accuracy is required, when readings appear unusual, or after cleaning the sensor.

How to Use

1. Remove the protective cap and rinse the probe with purified water.
2. Turn on the meter and confirm that the battery level is sufficient.
3. Immerse the probe approximately 3 cm or 1.18 inches into the nutrient solution.
4. Gently stir the meter to release trapped air bubbles.
5. Wait for the stability indicator to disappear.
6. Read the EC or TDS measurement on the main display and temperature on the secondary display.
7. Rinse the probe with clean water after testing.
8. Replace the protective cap before storing the meter.

For the most representative reading, test a well-mixed reservoir away from concentrated nutrient additions, dosing outlets, and recently added pH adjusters.

Calibration Best Practices

Calibration accuracy depends on the condition of the calibration standard. For the best results:

• Use fresh calibration solution for each calibration.
• Pour the required solution into a clean separate container.
• Never pour used calibration standard back into its original container.
• Rinse the probe with purified water before calibration.
• Avoid touching or wiping the graphite sensing surfaces.
• Replace contaminated or expired calibration solution.

Cleaning and Maintenance

Rinse the probe with clean water after every measurement. Nutrient residue, mineral deposits, or organic additives left on the sensor can interfere with response time and measurement stability.

If readings become slow, inconsistent, or difficult to calibrate, clean the sensing area with a compatible Hanna electrode cleaning solution. Rinse thoroughly before recalibrating.

Unlike a pH electrode, the HI98318 conductivity probe does not require storage solution. Replace the protective cap after cleaning and allow the meter to remain clean between uses.

Battery and Automatic Shutoff

The HI98318 operates on a replaceable CR2032 battery and provides approximately 250 hours of continuous use. The remaining battery percentage appears when the meter starts, and a low-battery symbol flashes when power drops below approximately 10%.

Automatic shutoff can be set for:

• 8 minutes
• 60 minutes
• Disabled

If the battery becomes too depleted for dependable measurements, the meter displays a battery warning and turns itself off.

What’s Included

• Hanna GroLine HI98318 EC/TDS tester
• Protective cap
• Hanna Quick Calibration Solution sachets
• CR2032 battery
• Quality certificate
• Instruction manual

Recommended Accessories

For reliable calibration and maintenance, pair the HI98318 with:

• Hanna GroLine Quick Calibration Solution
• Hanna GroLine 1413 µS/cm Conductivity Standard Solution
• Hanna General Purpose Cleaning Solution
• Clean calibration beakers or sample cups

Fresh calibration standards and routine sensor cleaning help maintain accurate, repeatable nutrient measurements.