One pen. Five parameters. Lab-grade pH and EC data for every feed check.
The Apera GroStar GS4 (AI104G) is a 5-in-1 combo pen tester that reads pH, EC, 500ppm, 700ppm, and temperature from a single instrument — built specifically for licensed cultivation operations that need reliable, repeatable nutrient solution data on every run.
The Apera GroStar GS4 is a second-generation, lab-grade combo pen tester designed from the ground up for the horticultural market. In a single handheld instrument, it delivers five critical measurements — pH, electrical conductivity (EC), TDS on both the 500 and 700 ppm scales, and solution temperature — without carrying two separate meters or switching between units mid-feed check.
At its core is a replaceable combo probe combining a double-junction pH sensor with a titanium conductivity sensor. The double-junction design resists contamination from nutrient-rich solutions, a known failure point on cheaper single-junction probes. The titanium EC sensor is built for longevity in the mineral-dense environments typical of hydroponic and coco-coir cultivation. When the probe reaches end of life, it's swapped out — the instrument body keeps running.
This pen is positioned for cultivation operations where consistency matters: licensed cannabis grows, hemp production facilities, commercial hydroponic operations, and any facility running multi-site or multi-room programs where staff are taking readings across canopy. The 5-in-1 parameter set eliminates the need for separate dedicated meters for pH and EC during daily fertigation checks, tissue testing prep, reservoir management, and runoff monitoring.
It's equally useful as a standard-issue field tool for lead growers and IPM techs who need a single calibrated instrument they can trust across multiple environments — from reservoir rooms to propagation chambers to outdoor flush stations. The IP67 waterproof and dust-proof rating means it survives the daily abuse of a working grow floor without requiring special handling.
The 3-color backlit LCD changes color by mode — white for measurement, green for calibration, red for calibration error — so staff can immediately confirm the pen's state at a glance, even in low-light or dark-period conditions. This is a practical detail that matters in facilities running lights-out schedules.
TruRead mode addresses multi-point data collection: the pen records individual readings as they stabilize, then automatically displays the average, minimum, and maximum across all recorded measurements. For facilities scouting runoff EC or pH across multiple pots or trays, this eliminates manual logging and averaging. Calibration is 2-point automatic with an on-screen electrode condition indicator that tells you when the probe is approaching calibration drift — so you're not guessing probe health. Automatic temperature compensation (ATC) keeps EC readings accurate as solution temps fluctuate through the day.
The GS4 is compatible with the full GroStar replacement probe lineup — pH, Soil pH, EC, and pH/EC Combo probes are all interchangeable with the same instrument body. A facility running both hydroponic reservoirs and a soil or coco propagation area can standardize on one pen platform and swap probes rather than maintaining entirely separate meter inventories.
The kit ships complete: pH 7 and pH 4 calibration solution (50ml each), 2.77 EC calibration solution (50ml), KCl storage solution (10ml), lanyard, and user manual. Everything needed for immediate deployment is in the box. The pen runs on standard AAA batteries with an auto-off function — no charging infrastructure required, which keeps pens operationally ready without coordinating charge cycles into shift schedules. HSC supplies the GS4 through direct accounts with Apera, available to licensed cannabis and hemp operators nationwide.
| SKU | AI104G |
| Series | GroStar GS4 (Gen II) |
| Parameters | pH, EC, 500ppm, 700ppm, Temperature (5-in-1) |
| pH Sensor | Double-junction replaceable probe |
| EC Sensor | Titanium conductivity sensor, replaceable |
| Calibration | 2-point automatic (pH); single-point (EC) |
| Display | 3-color backlit LCD (white / green / red by mode) |
| Waterproof Rating | IP67 |
| Power | AAA batteries with auto-off function |
| Warranty | 2 years (instrument) / 1 year (probe) |
| Kit Includes | pH 7 & pH 4 cal solution (50ml ea.), 2.77 EC cal solution (50ml), KCl storage solution (10ml), lanyard, user manual |
Probe only. The GS4 is built around a replaceable probe system — when the pH/EC combo probe reaches end of life, you swap it out and keep the instrument body. The pen is compatible with the full GroStar replacement probe lineup, including dedicated pH, Soil pH, EC, and pH/EC Combo probes.
Yes. The GS4 handles nutrient solution, coco coir, and other common grow media. For direct soil or media insertion, the GroStar Soil pH probe (GS2) is a compatible swap-in on the same pen body. The standard combo probe is optimized for liquid solution readings.
TruRead mode records each stabilized reading as you move through multiple measurement points, then displays the average, minimum, and maximum of all readings automatically. It's useful for runoff EC or pH scouting across multiple pots, rows, or reservoirs — you get aggregate data without manual logging.
The 500 and 700 refer to the TDS conversion factor applied to the EC reading. The 500 scale (NaCl-based) is common in North American nutrient programs; the 700 scale (KCl-based) is used by some European nutrient lines. Match the scale to whatever conversion factor your nutrient manufacturer references on their feed charts. The underlying EC value is the same — only the ppm display changes.
Yes. The IP67 waterproof and dust-proof rating handles daily grow floor conditions. The electrode condition display alerts staff when the probe needs recalibration or replacement, reducing the risk of undetected drift across shifts. The 2-year instrument warranty covers the pen body under normal operational use.
Get operator-direct pricing and availability. We supply licensed commercial cultivators nationwide.
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