Hanna GroLine Automatic pH Dosing System HI981412

The Hanna GroLine pH Dosing System HI981412 provides continuous pH monitoring and automatic pH adjustment for hydroponic reservoirs, greenhouse irrigation systems, fertigation tanks, and other recirculating nutrient solutions. By combining a pH controller, temperature-compensated process probe, and adjustable peristaltic dosing pump in one wall-mounted system, it helps growers maintain a more stable root-zone environment with less manual intervention.

The HI981412 can be configured to dose either an acid to lower pH or a base to raise pH. Adjustable control settings, color-coded alarms, low-level or flow-switch inputs, and programmable overtime protection help reduce the risk of excessive dosing.

Key Benefits

• Continuous pH monitoring: Measures the solution around the clock instead of relying exclusively on periodic handheld tests.
• Automatic pH correction: Activates the built-in dosing pump when the measured pH moves beyond the programmed control point.
• Adjustable dosing rate: The peristaltic pump delivers approximately 0.5 to 3.5 liters per hour.
• Proportional or on/off control: Choose the dosing behavior that best matches the reservoir volume, circulation rate, and strength of the pH-adjusting solution.
• Temperature compensation: The included probe measures temperature so pH readings can be compensated automatically.
• Integrated safety functions: Overtime protection, external level or flow-switch inputs, programmable alarms, and visual status indicators help growers identify problems quickly.
• Process-ready probe: The amplified probe helps reduce interference from nearby pumps, motors, and other electrical equipment.
• Weather-resistant enclosure: The IP65 wall-mounted controller is designed for demanding greenhouse and indoor growing environments.

How Automatic pH Dosing Works

The HI981412 continuously compares the measured pH with the grower’s programmed setpoint. When the pH moves outside the selected control range, the system activates its peristaltic pump and adds pH-adjusting solution.

Configure the system for the chemical being used:

• Use an appropriate acid or pH Down solution when the system is configured to lower pH.
• Use an appropriate base or pH Up solution when the system is configured to raise pH.
• Do not connect the wrong chemical for the selected dosing direction.
• This is a single-channel dosing system and should be connected to only one pH-adjusting solution at a time.

Consistent circulation is essential. The reservoir should remain well mixed during measurement and dosing so the probe detects a representative sample and concentrated adjuster does not collect in one location.

Measurement Specifications

• Controller pH range: 0.00 to 14.00 pH
• Probe pH range: 0 to 12 pH
• pH resolution: 0.01 pH
• pH accuracy: ±0.10 pH at 25°C
• Probe temperature range: -5 to 70°C / 23 to 158°F
• Temperature resolution: 0.1°C / 0.1°F
• Temperature accuracy: ±0.5°C / ±0.9°F
• Temperature compensation: Automatic

Dosing and Control Specifications

• Pump type: Integrated peristaltic pump
• Adjustable flow rate: 0.5 to 3.5 L/hour
• Maximum pump pressure: 1 bar / 14 psi
• Control direction: High or low pH control
• Control modes: Proportional or on/off
• Setpoint range: 4.00 to 10.00 pH
• On/off hysteresis: Adjustable from 0.10 to 1.00 pH
• Proportional control band: Adjustable from 0.10 to 2.00 pH
• Startup delay: Adjustable from 0 to 600 seconds
• Overtime protection: Adjustable from 1 to 180 minutes or disabled
• Manual priming: Allows the dosing line to be filled during installation and maintenance

HI10063 Process Probe

The included HI10063 is an amplified pH and temperature probe designed for continuous process monitoring. Its built-in amplification helps protect the measurement signal from electrical noise produced by pumps, grow-light ballasts, and other nearby equipment.

Probe features include:

• Integrated pH and temperature measurement
• Double-junction reference design
• Replaceable cloth junction
• Chemical-resistant PVDF body
• Matching pin for improved measurement stability
• Quick Connect DIN connection with a waterproof seal
• 3/4-inch NPT upper thread for reservoir installation
• 1/2-inch NPT lower thread for inline mounting
• Approximately 2-meter probe cable

For accurate readings, install the probe where it will receive steady circulation without being exposed to trapped air, concentrated pH adjuster, or excessive turbulence.

Display, Alarms and Protection

The multi-colored LCD provides an immediate indication of system status:

• Green: Normal measurement or control conditions
• Yellow: Attention or setup condition
• Red: Active alarm condition

Programmable high and low pH alarms alert the grower when the solution moves outside the desired range. The controller also accepts an external level or flow-switch signal, allowing it to stop dosing when the chemical container is empty or when adequate solution flow is not detected.

Overtime protection limits how long the pump can operate continuously. This provides an additional safeguard if the pH does not respond as expected, although it should not replace routine inspection of the reservoir and dosing equipment.

Calibration Options

The HI981412 supports automatic one- or two-point calibration using recognized pH standards:

• pH 4.01
• pH 7.01
• pH 10.01

A two-point calibration using pH 7.01 and the buffer closest to the working range generally provides the best accuracy. The controller also supports a single-point process adjustment of up to ±0.50 pH around the measured value.

Always use fresh calibration buffer, rinse the probe between solutions, and never pour used buffer back into its original container.

Installation Options

The HI981412 is available in configurations suited to different system layouts:

• Controller and probe configuration: Intended for growers who will supply their own mounting hardware, dosing fittings, and tubing.
• Inline installation configuration: Adds components for installing the probe and chemical injector in a recirculation pipe.
• Flow-cell installation configuration: Adds a flow cell and associated mounting components for routing a controlled sample past the probe.

Package contents vary by the selected configuration. Review the chosen variant before ordering to confirm whether inline or flow-cell installation hardware is included.

Installation Recommendations

• Mount the controller vertically in a location protected from direct sunlight, vibration, and continuous dripping water.
• Install the probe where it receives a representative, continuously circulating sample.
• Keep the chemical injection point downstream and an appropriate distance away from the probe.
• Do not inject concentrated pH adjuster directly onto the probe.
• Confirm that all tubing, fittings, seals, and containers are compatible with the chemical being dosed.
• Keep the dosing container clearly labeled and secured against spills.
• Have electrical wiring and permanent process connections completed by qualified personnel.
• Disconnect power before servicing the pump, tubing, wiring, or probe.

Routine Maintenance

For dependable automatic control:

• Inspect the dosing tube regularly for wear, flattening, brittleness, or leaks.
• Check suction and injection lines for air bubbles, clogs, and loose fittings.
• Clean the probe when readings become slow, unstable, or difficult to calibrate.
• Store and condition the pH electrode according to Hanna’s instructions.
• Never allow a pH electrode to dry out.
• Calibrate regularly using fresh pH buffer.
• Verify the controller periodically with a separate, properly calibrated handheld meter.
• Check the chemical supply and external level or flow-switch operation.
• Test alarms and overtime protection before leaving the system unattended.

Important Safety Information

pH Up and pH Down products may be corrosive. Wear appropriate gloves and eye protection, follow the chemical manufacturer’s Safety Data Sheet, and provide suitable ventilation.

Never mix concentrated acid and base products together. Start with a conservative pump setting and a properly diluted adjusting solution when appropriate for the application. Closely observe the system during initial setup to confirm that the pH changes gradually without overshooting the setpoint.

The HI981412 controls pH only. It does not monitor electrical conductivity, TDS, or nutrient concentration. Growers who need automated nutrient-strength control can pair it with a separate Hanna GroLine EC/TDS dosing controller.