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Capacitive vs resistive soil moisture sensor

Updated: 23 October 2026

If a probe will sit in damp compost for weeks, the capacitive vs resistive soil moisture sensor choice matters more than the brand. Resistive forks pass current between metal prongs and slowly eat themselves. Capacitive boards sense a dielectric change with far less electrolysis. A battery-free metal dial is a third category: spot-check only. Named picks are on the [best soil moisture meter](/hub/garden-watering/soil-moisture-sensor/sub/soil-moisture-sensor-best) page and the [soil moisture sensor comparison](/hub/garden-watering/soil-moisture-sensor). Listings were checked on 21 October 2026. There was no lab test. A purchase can earn a commission at no extra cost to you.

If a probe will sit in damp compost for weeks, the capacitive vs resistive soil moisture sensor choice matters more than the brand. Resistive forks pass current between metal prongs and slowly eat themselves.

Our top picks

XLUX XLUX soil moisture meter (no batteries)

Best overall

XLUX XLUX soil moisture meter (no batteries)
8.8/10about £9.99
View offer
Hailege Hailege LM393 resistive sensor + relay, 2pcs

Alternative

Hailege Hailege LM393 resistive sensor + relay, 2pcs
8.4/10about £7.49
View offer
THIRDREALITY THIRDREALITY Zigbee soil moisture Gen2

Alternative

THIRDREALITY THIRDREALITY Zigbee soil moisture Gen2
7.2/10about £19.99
View offer
On this page
  1. 1.How each sensor measures moisture
  2. 2.Corrosion and drift
  3. 3.DIY buying rule
  4. 4.Smart garden sensors
  5. 5.Where analogue dial meters fit

How each sensor measures moisture

A resistive probe is usually a two-prong fork plus a comparator, often an LM393. Wet soil conducts better between the prongs, so the voltage changes and a threshold can flip a relay or feed an analogue pin. The kits are cheap and simple to wire. Continuous current and dissolved minerals attack the metal. A capacitive sensor uses a coated or PCB area that forms a capacitor with the soil. Water changes the dielectric constant without the same fork-to-fork electrolysis, which is why write-ups treat capacitive modules as the longer-contact option. You still calibrate wet and dry for your soil. More durable is not laboratory volumetric water content out of the box.

Corrosion and drift

A powered resistive fork in a moist bed typically discolours, pits and drifts in a short project life, sometimes days of continuous use rather than a season. Green crust is the visible warning. Silent drift is worse, because a dying sensor can keep a valve open. Metal dials avoid a continuous bury, but they corrode if forgotten for days. Remove the tip after a few minutes. Capacitive sensors reduce that mode. They are not immortal: flood the electronics, scratch a coating, or mismatch 3.3 V and 5 V and the board still dies. A dead unit in a multipack is quality control, not a reason to bury a resistive fork all summer. A weekend bench demo can stay resistive.
XLUX XLUX soil moisture meter (no batteries)

Testsieger

XLUX XLUX soil moisture meter (no batteries)
8.8/10about £9.99
View offer

DIY buying rule

Capacitive five-packs for Arduino and Raspberry Pi are the bury-oriented DIY lane. APKLVSR (B0CQNF7S7L) is about £7.99, with 4.1 from 54 reviews, at 98 mm by 23 mm with a 3-pin header. XuanQiMY’s five v1.2 boards are about £7.59 and have no customer-review line on the capture. Both need your wiring, code and wet-dry calibration. The Hailege LM393 kit, about £7.49 with 4.2 from 12 reviews, is the learning lane: a relay click on the bench. Buy resistive for that demo. Buy capacitive when the probe stays damp. Cheaper does not make a resistive fork a permanent bed sensor, and neither pack is a finished dial. An I2C temperature shell answers a different question. Placement is in how to use a soil moisture meter.

Smart garden sensors

Zigbee sensors that market capacitive monitoring, such as THIRDREALITY Gen2, put the same bury logic in a finished shell. The element stays in the pot or bed, on a cell, talking to a hub. You pay for casing and radio instead of soldering, and you inherit hub cost and stem height. Capacitive wording supports stay-in use. It does not prove lab accuracy. Naked metal forks in the photos are resistive. Keep that bury short. Any valve automation needs a maximum runtime. A fork stuck on dry is a classic way to empty a water butt.

Where analogue dial meters fit

A battery-free dial with a single metal probe is a handheld spot-check, not a capacitive stay-in sensor and not a resistive project fork. You insert, read, wipe and store. Leaving the tip as decoration corrodes it. Dials win on zero wiring. The rule is still not to leave them in. Choose a dial for occasional readings without a hub or code. Choose capacitive stay-in for continuous data. Choose resistive only for a short demo. That split sorts most of the mixed amazon.co.uk results.

Common questions

Which lasts longer in soil?
Capacitive designs are the better long-bury choice. Resistive forks corrode and drift when left powered in damp soil. Analogue dial meters should not stay buried between checks. Durability is not the same thing as a laboratory volumetric water content reading.
Why do resistive probes go green?
Electrolysis and mineral deposits attack the exposed metal while current flows through wet soil. The green crust is corrosion, and the reading usually drifts as the metal changes. That is expected wear on a powered fork, not a rare defect in one pack.
Are analogue dial meters capacitive?
Typically no. Common garden dials use a metal probe for a brief reading and are sold as insert-and-remove tools, not as capacitive stay-in sensors. Take the tip out after a few minutes, wipe it, and store the meter dry.
Do Zigbee garden sensors use capacitive probes?
Many marketed stay-in models do, including the THIRDREALITY Gen2 example in this comparison. Read the listing. Capacitive language supports a bury. Naked resistive forks do not. You still need the hub the listing names.
Can I use resistive boards for a weekend demo?
Yes. They are fine for a short learning project and a relay demo. Plan to replace them if you later need a permanent bed sensor, and move to a capacitive board for that job. Do not leave the fork powered in damp compost for the season.
Do capacitive modules need calibration?
Yes. You still map wet and dry endpoints for your soil and your microcontroller. Longevity improves versus resistive forks. Absolute lab accuracy is a separate claim that cheap boards do not earn automatically.

Related pages

Soil moisture meter buying guide

Soil moisture sensor

Best soil moisture meter UK: dial, value or Zigbee

Soil moisture meter hosepipe ban: what still works

How to use a soil moisture meter for pots and beds

Sources

Public UK sources for temporary use bans, product marking and the limits of cheap meters. amazon.co.uk prices, stars and review counts are the saved listing lines for these twelve products. Last reviewed 22 October 2026.

  1. Ofwat, hosepipe bans and non-essential use bans (retrieved 22 October 2026)
  2. Water UK, hosepipe ban FAQs (retrieved 22 October 2026)
  3. GardenScout, choosing a soil pH and moisture meter (retrieved 22 October 2026)
  4. Gardens Illustrated, soil moisture meters (retrieved 22 October 2026)
  5. amazon.co.uk, XLUX soil moisture meter (retrieved 22 October 2026)
  6. arXiv, resistive versus capacitive soil moisture sensors (retrieved 22 October 2026)
  7. GOV.UK, UKCA and CE marking in Great Britain (retrieved 22 October 2026)