Apera GroStar® GS4 5-in-1 Combo Pen Tester (Gen II) — pH, EC, ppm & Temperature in One Device
The Apera GroStar GS4 Gen II is the ultimate all-in-one pen tester for growers who want to monitor every critical water quality parameter without carrying multiple meters. In a single dip, the GS4 simultaneously measures pH, EC, 500 ppm (NaCl), 700 ppm (KCl), and temperature — giving you the complete nutrient and pH picture for your crop, every time.
Key Features
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5-in-1 Simultaneous Measurement — pH, EC, 500 ppm, 700 ppm, and temperature in a single probe insertion; replace two meters with one
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Dual-Sensor Combo Probe — Double-junction pH sensor for accurate, contamination-resistant pH readings + titanium conductivity sensor for reliable, long-life EC/ppm measurement
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Replaceable Combo Probe — When the probe ages, swap it out — protect your investment without replacing the full pen
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TruRead™ Measurement Mode — Measure across multiple reservoir zones or plant sites and automatically display average, minimum, and maximum values for comprehensive grow monitoring
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Dual ppm Scales — Supports both 500 ppm (NaCl) and 700 ppm (KCl) conversion factors for universal compatibility with any nutrient line or feeding chart
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2-Point Automatic Calibration — Simple workflow with electrode condition display for real-time probe health monitoring
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3-Color Backlit LCD — Clear readings in any lighting; color-coded by mode for instant status recognition
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Grower-Optimized Design — Streamlined for daily use in grow rooms, greenhouses, and hydroponic systems
Measurements at a Glance
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pH — Nutrient solution acidity/alkalinity
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EC — Electrical conductivity (nutrient strength)
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500 ppm — NaCl conversion scale
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700 ppm — KCl conversion scale
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Temperature — °C / °F
Applications
Hydroponics, aquaponics, cannabis cultivation, greenhouse growing, nutrient solution monitoring, reservoir management, coco coir, rockwool, and general water quality testing.
Why GroStar GS4 Over Separate Meters?
Carrying a separate pH pen and EC meter means double the calibration, double the maintenance, and double the cost when probes age. The GS4 consolidates everything into one device with a single replaceable combo probe, dual ppm scales for any nutrient line, and TruRead™ multi-point averaging — the most grower-intelligent 5-in-1 pen available.
