GroStar pH/ORP Pen Tester Kit with ORP Probe

What the GS1-P Is

The Apera GroStar GS1-P is a Gen II lab-grade pen tester that measures pH, ORP (oxidation-reduction potential), and temperature from a single handheld instrument. The kit ships with two interchangeable probes: a replaceable double-junction pH probe built with a low-impedance lithium glass membrane and blue gel inner electrolyte, and a replaceable platinum ORP probe. Swapping probes automatically shifts the meter into the corresponding measurement mode — no menu navigation required.

The pen body carries an IP67 waterproof and dust-proof rating, making it suitable for humid grow rooms, fertigation stations, and reservoir decks where splash exposure is routine. It runs on AAA batteries with an auto-off function to preserve battery life between checks.

Who This Instrument Is For

The GS1-P is the right tool for operations that need to track both nutrient solution pH and disinfection efficacy in the same workflow. If your facility runs a recirculating hydroponic or aeroponic system and doses with chlorine, hydrogen peroxide, ozone, or another oxidizing sanitizer, ORP is the fast, direct measure of how much active disinfectant is in solution. Monitoring ORP alongside pH catches drift in both parameters before plant stress or pathogen pressure develops.

It's also a practical choice for multi-site compliance grows where technicians move between rooms or buildings and need a single instrument that covers both checks. The replaceable probe design means you replace the consumable sensor, not the entire meter, reducing long-term cost across a team of testers.

Key Features for Commercial Use

The double-junction reference system on the pH probe is specifically designed to resist contamination from nutrient-rich and organic-laden solutions — a common cause of sensor drift in single-junction probes used in cannabis fertigation environments. The anti-contamination architecture extends probe service life and maintains reading accuracy between calibration cycles.

TruRead measurement mode lets technicians take readings at multiple sample points and automatically logs the average, minimum, and maximum values across all readings — useful for verifying uniformity across a reservoir or across multiple grow sites in a single walkthrough. The 3-color backlit LCD (white for measurement, green for calibration, red for error) remains legible in low-light growing environments. Quick 2-point automatic calibration with an electrode condition display tells the operator whether the probe is still performing within spec before they rely on a reading.

What's in the Kit & How It Fits a Build

The AI201G kit includes the GS1-P pen tester with replaceable double-junction pH probe, a replaceable platinum ORP probe, pH 7 and pH 4 calibration buffer solutions (50 mL bottles each), 3M KCl storage solution (10 mL bottle), lanyard, and user manual. Everything needed to calibrate and begin measuring out of the box is included — no separate accessory orders required to get started.

In a standard commercial cannabis build, the GS1-P fits daily or shift-based quality checks at the reservoir, fertigation dosing point, or runoff collection. For operations running UV, peroxide, or ozone-based pathogen control in their recirculating lines, pairing pH and ORP monitoring at the same check interval is standard protocol. The instrument's compact pen format makes it easy to route through a walk-and-check SOPs without the bulk of a benchtop meter. Backed by Apera's 2-year instrument warranty and 1-year probe warranty.