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SKU HI981421 Category

Monitor for Hydroponic Nutrients GroLine (Inline Probe) - HI981421

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The Monitor for Hydroponic Nutrients, HI981421 GroLine provides around-the-clock, continuous monitoring of pH, conductivity (EC & TDS), and temperature in hydroponic nutrient solutions. Quick to setup, simple to use, this monitor was designed with Hydroponics, Aquaponics, and Greenhouses in mind. Make your nutrient solution easy to manage with the GroLine Monitor.

  • Get 24/7 pH&EC measurements for consistent yields every time.
  • Good Laboratory Practice (GLP) feature for professional accuracy.
  • Calibrate pH and EC with a single Quick Cal solution.

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Monitor for Hydroponic Nutrients – Key Features

One quick glance is all it takes.

A large clear LCD displays all of your essential readings so you know what your hydroponic nutrients solution is doing 24/7. High and low alarms flash warning you if something needs adjusting.

Monitor changes over time.

The Monitor for Hydroponic nutrients automatically logs your results every 15 minutes over the last 30 days. Minimum, maximum, and average values are stored so you can recognize when patterns arise and help prevent future problems.

One probe. Three measurements.

Our 3-in-1 pre-amplified inline probe measures pH, EC/TDS, and temperature in a single, durable, polypropylene body making the GroLine Monitor easy to handle and easy to set up. The HI1285-9 has a 3/4” threaded connection for insertion into a pipe for flow through monitoring.

Monitor for Hydroponic Nutrients

Quick Cal for less maintenance.

A single calibration solution for pH and conductivity makes calibration fast and ensures all of your measurements are accurate all of the time for better plant health and better yield.

Professional level accuracy.

Advanced algorithms and greater pH and TDS/ppm accuracy ensure operational consistency and a finer understanding of your plant’s nutritional needs.

Measure like a pro.

Our GroLine Monitor is made by growers and scientists alike who are committed to helping you take your growing operation to the next level.

Monitor for Hydroponic Nutrients – Features at-a-glance

  • 3 sensors combined in a single rugged probe body made for continous immersion up to 2 meters: pH electrode with renewable cloth junction, amperometric EC/TDS sensor, and an internal temperature sensor for temperature compensated readings
  • IP65 rated enclosure: designed to withstand harsh grow environments
  • Wide pH Range: measure pH from 0.00 to 14.00 pH
  • Selectable EC to TDS/ppm conversion factor: choice of either a 0.5 or 0.7 conversion factor
  • Automatic Temperature Compensation: all readings are compensated for variations in temperature, temperature displayed in oC or oF along with pH, EC or TDS reading
  • Large LCD with plant-friendly green backlighting: LCD can display all three essential hydroponic nutrient measurements at one time, a 3-second cycle of single measurements, or a real-time graph screen with options for measurement selection and log recall
  • Data logging for 30 days: logs every 15 minutes for last 30 days, stores min, max, and average values
  • Data transfer: USB-C port for easy data transfer to memory stick or PC
  • High and low alarms: warns when your nutrient solution is out of desired range by flashing display and message
  • Ambient light sensor: for automatic LCD dimming


pH Resolution0.01 pH
pH Accuracy (@25°C/77°F)±0.05 pH
Temperature Range0.0 to 60.0°C / 32.0 to 140.0°F
Temperature Resolution0.1°C / 0.1°F
Temperature Accuracy (@25°C/77°F)±0.5°C /±1°F
EC Range0.00 to 10.00 mS/cm
EC Resolution0.01 mS/cm
EC Accuracy (@25°C/77°F)±0.1mS/cm (0.00 to 5.00mS/cm); ±0.2mS/cm (5.00 to 10.00mS/cm)
TDS Range0 to 5000 ppm (TDS conversion factor 0.5 (500 CF)); 0 to 7000 ppm (TDS conversion factor 0.7 (700 CF))
TDS Resolution10 ppm
TDS Accuracy (@25°C/77°F)±2% F.S.
Temperature CompensationpH: automatic (0.0 to 60.0ºC/ 32.0 to 140.0°); EC: automatic with β set at 1.9%/°C
CalibrationpH calibration at one or two-point calibration (using pH 4.01,7.01, 10.01 buffers) using auto buffer recognition; one-point calibration using quick calibration solution; EC calibration at one-point at 1.41 mS/cm or 5.00 mS/cm using auto standard recognition; one-point calibration using quick calibration solution
Log FeatureAutomatic logging for last 30 days at 15 minute interval
AlarmsHigh and Low with enable/disable option for all parameters
ConnectivityUSB Type-C
GLPGood Laboratory Practice with last 5 pH and EC calibration history
Power Supply12VDC adapter (included)
Environment-5 to 50°C (23 to 122°F); RH max 95% non-condensing
Dimensions125 x 185 x 38 mm (4.92 x 7.28 x 1.49”)
Weight333g ( 11.7oz.)
Ordering InformationHI981421 is supplied with HI1285-9 multiparameter probe, Quick Cal buffer solution sachets (2), HI700661 electrode cleaning solution sachets for agriculture (2), 12VDC power adapter, quality certificates and instruction manual.

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