Digital Thermohygrometer with Probe TH3 – Cornwall Electronics · Precision Climate Control

The Digital Thermohygrometer with Probe TH3 by Cornwall Electronics is the definitive tool to stop flying blind in your indoor grow, allowing you to measure temperature and humidity with surgical precision exactly where your plants need it most.

Why is your crop failing even though you have the best equipment?

You have invested in top-quality seeds, a powerful light, and good fertilizers, but your plants still show signs of stress, slow growth, or even the beginning of fungal issues. You look at the thermometer on the wall of the tent, and it says everything is fine. This uncertainty is one of the most common problems for growers: trusting a measurement taken in the wrong place.

There is nothing more frustrating than seeing curled leaves or stalled buds and not knowing why. If you measure the temperature on the wall or floor, you are lying to yourself. The heat accumulates differently under the spotlight than in the corners. If you don't know the real environmental conditions your "girls" are suffering, you can't fix them. A few degrees too many or uncontrolled humidity can ruin months of work in days.

The Digital Thermohygrometer with Probe TH3 solves this immediately. Thanks to its 1.5-meter probe, you can place the sensor right at the canopy level (the tips of the plants), which is the critical hot spot, while leaving the screen attached to the structure or even outside the grow tents to read the data without opening the zipper and altering the microclimate. It gives you the truth, and the truth gives you big buds.

If you’re just starting out: how this product helps you

When you start growing, there are too many variables to control. This device simplifies your life because it is "Plug & Play": you put the battery in, place the probe, and you instantly know if your environment is safe for cannabis. You don't need calibration or complex setups.

• Easy reading: Its large LCD screen allows you to see the data at a glance without straining your eyes.
• Safety margin: By knowing the real temperature at the plant tips, you avoid burning them with the lamp, a classic beginner mistake.
• Dual function: It measures temperature and humidity simultaneously, saving you from buying two different devices.

If you already have experience: why it deserves a place in your kit

For the veteran grower, data is power. The TH3 is not just a thermometer; it is a diagnostic tool. Its Max/Min memory function is vital: it tells you how much the temperature dropped at night or how high the humidity spiked when the extraction turned off. This allows you to fine-tune your climate control to the millimeter.

• Strategic placement: The 1.5m cable allows you to monitor different points of the room (pots, canopy, air intake) without moving the device.
• Pest prevention: By strictly controlling humidity peaks, you can anticipate the appearance of botrytis or powdery mildew before they become visible.
• Equipment check: It helps you verify if your extraction and ventilation cycles are working as they should during the dark period.

Advantages and benefits for any level

• External Probe (Feature): A sensor located at the end of a 1.5-meter cable. Advantage: Allows measuring in difficult-to-access areas or directly under the light without damaging the screen. Benefit: You get real data from the plant's environment, preventing heat stress and burns.
• Max/Min Memory (Feature): Records the highest and lowest values reached since the last reset. Advantage: You don't need to be in front of the tent 24 hours a day. Benefit: Total peace of mind knowing that you have control over what happens in your crop while you sleep or work.
• Large LCD Screen (Feature): Clear display of values. Advantage: Quick interpretation of data. Benefit: Saves time and avoids confusion when checking parameters daily.
• Compact Design (Feature): Dimensions of 11 x 7 x 1.5 cm. Advantage: Takes up very little space and is easy to hang. Benefit: Keeps your grow space tidy and professional.
• Wide Range (Feature): Measures from -30ºC to 70ºC and 20% to 90% humidity. Advantage: Covers all possible growing scenarios. Benefit: Versatility to use it in drying rooms, propagation, or flowering.

Typical mistakes this product helps you avoid

Many crops fail not because of a lack of love, but because of a lack of accurate information. This Cornwall Electronics device is your shield against common errors.

• The "Ostrich Effect": Thinking that because the room is cool, the inside of the tent is too. The probe reveals the heat pockets that stifle your plants.
• Ignoring the night: Many problems (mold, stretching) happen when the lights go out. The Max/Min memory reveals if your temperature drops too much or humidity skyrockets in the dark.
• Opening the tent too much: By being able to leave the screen outside (passing the cable through a sleeve), you check the parameters without opening the tent, maintaining the stability of the environment.

Frequently Asked Questions

Does the probe measure both temperature and humidity?

No, usually in these standard models, the probe measures temperature, while the humidity sensor is located in the main body of the device. Therefore, it is ideal to place the body inside the tent at a medium height and the probe at the tips of the plants to control the heat of the focus.

How do I reset the Max/Min memory?

It's very simple. Press the "Reset" button (or hold the Max/Min button depending on the version) for a few seconds. We recommend doing this every day at the same time (for example, when the lights turn on) to have a daily control of the cycles.

What batteries does it use?

It works with a standard 1.5V AAA battery (usually included, but it's always good to have a spare). It has very low consumption, so a single battery can last for months of continuous use.

Can I use it for curing in jars?

Although it is accurate, the device is a bit large for standard jars and the probe is designed for larger spaces. For curing, we recommend smaller mini-hygrometers that fit inside the jar. This model is perfect for the humidity controller management of the room or the drying closet.

Personal Experience of Pevgrow’s CEO (Alan)

If I had to choose only one measuring tool for a budget setup, it would be this one. I recommend it to all my friends who start because it is cheap and indestructible. When I started, I made the mistake of trusting the analog thermometer stuck to the wall, and I burned several tips. Since I started using the probe at the height of the flowers, my production improved noticeably.

Even now, with more automated systems, I always have a couple of these TH3s around the room as a "backup" to double-check that the climate controllers are telling the truth. It is a small investment that saves you a lot of headaches.