Judging from your equipment list, you are focusing on multi‑depth tubular soil‑monitoring devices. When selecting a pH sensor, you need to first confirm your monitoring type, then check core parameters and durability.
📝 Step 1: Select your monitoring method Based on your list (3‑layer tube, 4‑layer tube) and field‑application scenarios, there are two main options:
- Tubular Type (Layered Monitoring) This is the model shown on your list. Sensors are sealed inside a PVC tube and inserted underground to collect data from multiple soil depths simultaneously. It is especially ideal for scientific research and high‑standard farmland projects requiring soil‑profile data analysis. Since sensors are not in direct contact with soil, they deliver longer service life and more stable readings. Installation is slightly more complex, and the cost is relatively higher.
- Probe‑in Type (Direct‑insert Monitoring) Metal probes are inserted directly into the soil for measurement. This type features simple, flexible installation, and suits rapid spot‑checks or fixed monitoring for large farmland and orchards. The downside is that long‑term buried probes are at risk of soil corrosion.

✅ Step 2: Check key technical specifications After confirming your sensor type, compare products against these core indicators:
- Accuracy & Measuring Range: For general agricultural use, a pH accuracy of ±0.3 pH and a measurement range of 3‑9 pH are sufficient. For scientific‑research‑grade or high‑precision projects, pick high‑accuracy sensors with ±0.1 pH tolerance.
- Protection & Material: For long‑term underground burial, an IP68 waterproof rating is mandatory. Direct‑insert probes should be made of 316 stainless steel or special‑purpose alloy for anti‑corrosion performance.
- Communication & Power Supply: RS485 with the Modbus protocol is the mainstream solution, which offers strong anti‑interference performance for network deployment. For off‑grid field sites, choose low‑power‑consumption sensors that support solar power supply.

Given your 3‑layer tubular‑sensor setup, the layered tubular monitoring solution is most likely the better fit for you. Before purchasing, confirm with your supplier whether the pH sensor can be integrated into your multi‑layer tubular monitoring system.

What kind of soil‑monitoring project are you working on? If you can share details about your target crops or application scenarios, I can help you evaluate whether the tubular sensor is your optimal choice.