Hanna GroLine Multiparameter Probe HI1285-8 | pH, EC, TDS + Temp Electrode, HI981420

What the Hanna GroLine Multiparameter Probe Carries in One Body

The HI1285-8 is three sensors in one polypropylene body, built for continuous immersion in a hydroponic reservoir on the HI981420 GroLine monitor. The pH half is a spheric glass bulb, 8.5 mm across, on a single Ag/AgCl reference with a gel electrolyte and a cloth junction. It covers pH 0 to 13 and 0 to 50 °C, and the glass is marked LT for low temperature work. A built-in amplifier sits in the probe itself. Pumps, ballasts and fan motors put electrical noise onto a high impedance pH signal. Amplifying it at the glass rather than at the meter is what keeps the reading steady in a grow room. The cloth junction is the part that makes it a working electrode rather than a disposable one. When the reading drifts or goes erratic, the cloth can be drawn out a little to expose a fresh surface. The probe then goes back to work. The EC and TDS half is a two-pin amperometric sensor. An alternating voltage goes across two stainless steel pins and the current that passes between them is read as dissolved ionic solids. On the HI981420 that gives 0.00 to 10.00 mS/cm and up to 5,000 or 7,000 ppm depending on the TDS factor. A temperature sensor in the same body feeds the monitor's compensation. Both pH and EC are corrected to the solution's temperature as it changes through the day. The lead is a 7-pole cable on a DIN connector, 1 m long. The body is rated to 0.2 bar, which is a tank, not a pressurised line. The polypropylene stands up to fertilizer salts and the acids and bases used to steer pH. Hanna warrants the probe for six months, and it ships at about 0.65 lb.

Keeping a Hanna pH Probe Replacement Accurate for Its Whole Life

A hanna ph probe replacement earns its keep by how it is treated in the first hour and every fortnight after. If the bulb or the junction arrives dry, soak the tip in HI70300 storage solution for at least an hour before the first calibration. Calibrate on the HI981420 with the probe at least 4 cm into the buffer and stirred gently. Use pH 7.01 first, then 4.01 for an acid-side room or 10.01 for an alkaline one. Set EC against the 1.41 or 5.00 mS/cm standard and confirm when the reading settles. Hanna's schedule for this probe is a calibration every two weeks as routine maintenance. A thorough clean every two months in HI700661 cleaning solution for agriculture goes with it. Mount it in the tank on the HI60501 immersion holder with the bottom of the probe always under the solution. Keep it away from the return line and the dosing inlet. A probe in the splash zone reads air half the time and the monitor logs nonsense. Keep it out of the direct stream of an air stone too, because bubbles across the EC pins read as a drop in conductivity. Rinse the tip in clean water after a cleaning, never wipe the glass, and never store it dry. Between uses the sponge in the cap stays wet with HI70300 or 3.5 M KCl. Distilled water is the one thing it must never sit in. When a reading starts to wander between calibrations, pull the cloth junction out a millimetre to refresh it before blaming the glass. Write the install date on the cable with a marker. A pH bulb ages whether it is used or not. The date is what tells a grower that a drifting reading is a tired probe and not a tired reservoir.

Key Features

• pH, EC, TDS and temperature: Three sensors in one polypropylene body for the HI981420.
• Pre-amplified pH: The amplifier sits in the probe, so pump and ballast noise stays off the reading.
• Cloth junction, gel electrolyte: The cloth draws out to expose a fresh surface when readings drift.
• Two-pin amperometric EC/TDS: Stainless steel pins; 0.00 to 10.00 mS/cm on the monitor.
• Built-in temperature sensor: Compensates pH and EC to the solution temperature.
• 8.5 mm spheric LT glass: pH 0 to 13, 0 to 50 °C, single Ag/AgCl reference.
• 7-pole DIN connector: Plugs straight into the HI981420.
• Six month warranty: Hanna recommends calibration every two weeks and a clean every two months.

Technical Specifications