GroStar GS4 5-in-1 Combo Pen

One Pen, Five Readings, Zero Extra Gear to Juggle

Carrying separate pH and EC meters means twice the calibration, twice the storage solutions, and twice the chances of grabbing the wrong pen mid-feeding — friction that adds up over a season of regular checks.

The GroStar GS4 collapses that into one tool. It's a true 5-in-1 instrument, reading pH, EC, PPM (500 scale), PPM (700 scale), and temperature from a single lab-grade probe — so one calibration routine and one pen cover everything your nutrient program asks you to track.

It carries the same build quality as the rest of the GroStar lineup: a replaceable double-junction probe, a large 3-color backlit display, and an IP67 waterproof rating, plus compatibility with all GroStar replacement probes if you ever need to swap sensor types.

Key Features & Benefits

• Measures pH, EC, PPM (500), PPM (700), and temperature — covers your full nutrient-monitoring routine from a single lab-grade probe.
• Replaceable double-junction probe — lets you swap in a fresh sensor (GS4-E) instead of replacing the whole instrument at end of life.
• Compatible with all GroStar replacement probes — gives you flexibility to adapt the pen to different measurement needs down the road.
• Large 3-color backlit screen — keeps every one of those five readings clear and easy to scan, in any lighting.
• IP67 waterproof rating — stands up to the splashes that come with frequent reservoir and feed-tank checks.
• Full calibration kit included — ships with pH 7, pH 4, and 2.77 EC calibration solutions, KCL storage solution, lanyard, and manual.

Who Should Use the GroStar GS4

The GS4 suits growers who'd rather carry one combo instrument than juggle separate pH and EC pens — particularly anyone running a tight feeding schedule who wants every reading from a single calibration and a single tool.

Choosing the Right GroStar Pen for Your Setup

GroStar's pen lineup is built around what you need to measure: the GS1 covers pH and temperature, the GS2 adds a soil-rated spear probe, the GS3 reads EC/PPM and temperature, and the GS4 combines all of it in one 5-in-1 tool. If you're tracking both pH and conductivity regularly, the GS4 saves you from carrying — and calibrating — two separate pens.

Frequently Asked Questions

What does the GS4 measure?

It measures pH, EC, PPM on the 500 scale, PPM on the 700 scale, and temperature — all five from one lab-grade probe in a single reading.

Can I replace the probe?

Yes — it uses a replaceable double-junction probe (GS4-E), and the pen is compatible with all GroStar replacement probes.

What's included in the box?

It ships with a full calibration kit — pH 7, pH 4, and 2.77 EC calibration solutions — plus a KCL storage solution, lanyard, and user manual.

Is it waterproof?

Yes — it carries an IP67 waterproof rating and a large 3-color backlit screen for easy reading in any light.

Why choose the GS4 over the GS1 or GS3?

If you regularly track both pH and conductivity, the GS4 combines both functions — plus temperature — into a single instrument and calibration routine, instead of maintaining two separate pens.