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GroLine pH/EC/TDS Multiparameter Probe (Inline)


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The HI1285-9 inline multiparameter probe measures pH, EC/TDS, and temperature in one convenient, rugged probe.

Use with the HI981421 GroLine Monitor to provide around-the-clock, continuous monitoring of pH, conductivity (EC & TDS), and temperature in hydroponic nutrient solutions.

  • In-line pH, EC, & TDS probe with exclusive PTFE non-clogging membrane.
  • Built-in temperature sensor ensures fast, accurately compensated readings even during sudden temperature fluctuations.
  • Specialized for hydroponics with a renewable junction for extended life.


Hanna Instruments offers a wide variety of electrodes that are designed for many different applications. The sensing material, body material, and connection type used are just some of the design considerations.

HI1285-9 Inline GroLine pH/EC/TDS Multiparameter Probe

Pre-Amplified pH Electrode

The pH electrode circuit has a built-in amplifier that serves to reduce the effects of electrical noise on the high impedance pH measurement. Electrical noise can come from motors and pumps that are common in greenhouses. The single reference junction design of the pH electrode has a cloth junction that allows ion movement between the inner gel electrolyte and the sample being measured. The advantage of the cloth junction is that it can be extracted from the probe, exposing a fresh surface when readings become drifty or erratic. These features make this probe ideal for use in fertilizer solutions.

Amperometric EC/TDS Sensor

EC/TDS readings are performed by a two-pin amperometric sensor. An alternating voltage is applied to the sensor and the amount of current that passes between the two stainless steel pins determines the amount of dissolved ionic solids present.

Built-In Temperature Sensor

pH and EC/TDS readings must be temperature compensated in order to obtain accurate results. The built-in temperature sensor of the HI1285-8 provides a speedy temperature reading which is then used to adjust the pH and EC/TDS results accordingly.

PVC Body

The PVC body of the HI1285-9 houses all three sensors within a sturdy, single body design. This body material is suitable for a wide range of applications and excels in harsh grow environments due to its durability. PVC is chemically resistant to many aggressive chemicals and minimizes breakage due to accidental bumping or dropping of the electrode.

DIN Connector

The HI1285-9 uses a DIN connector. This probe is recommended for use with the HI981421 GroLine Hydroponic Nutrients Monitor for pH, EC, TDS, and Temperature.


Measurement Range pH: 0 to 12, EC
Junction Type/Flow Rate PTFE
Type of Electrolyte polymer
Body Material PVC (thread 3/4” NPT)
Tip / Shape dome
Matching Pin yes
Max. Pressure 8 bar
Temperature Operating Range 0 to 60°C (32 to 144°F) - GP
Overall Length 190 33
Temperature Sensor yes
Outer Diameter 32 mm
Cable 7-pole; 3 m cable (9.9’)
Connector Type DIN
Amplifier yes
Recommended Use Hydroponics, Aquaponics, and Greenhouses

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