SHT20 Temperature and Humidity Sensors, Probes and Transmitters

Choosing an SHT20 temperature and relative-humidity solution

Compare SHT20 digital temperature-and-humidity ICs, I²C breakout modules, cable probes and RS485/Modbus transmitters for embedded monitoring. This is a broad search-oriented collection rather than one interchangeable sensor platform. The same listings also offer SHT21/SHT25, SHT30/SHT31/SHT35, SHT40/SHT41/SHT45, SHTC3, HTU21D, Si7021, HDC1080, AHT10/AHT20/AHT21/AHT30 and DHT11/DHT22/AM2302 alternatives, plus bare carrier PCBs, controllers, ESP8266 accessories and two unrelated gas sensors. The selected variant, not a multichip headline, establishes which part ships.

What SHT20 measures

An SHT20-class device provides digital measurements of ambient relative humidity and temperature, commonly read through an I²C-compatible interface on appropriate breakout or probe assemblies. Relative humidity depends on temperature and local air exposure; a sensor in a warm sealed enclosure may report a different value from open air beside it. A chip, a cabled probe and a Modbus transmitter have different supply, connector, firmware and environmental limits. Do not apply a headline's “0–100%RH,” “-40 to 125°C,” “high precision” or “industrial grade” to every option or to the entire installed assembly. Resolution, stated tolerance, operating span, long-term drift and actual system accuracy are distinct engineering quantities and should be checked in the chosen part's data sheet and assembly documentation.

The sensing surface needs access to representative air while being protected from liquid water, dust, flux residue, adhesives and volatile contaminants. A stainless housing or breathable membrane may protect the sensing element but can change response time and does not, by itself, establish an IP rating, continuous immersion suitability, chemical resistance or soil-moisture measurement. “Waterproof” in a cable-probe title should be evaluated at the tip, membrane, cable joint and connector separately. Many humidity elements are intended for air exposure, not burial in wet soil or direct contact with liquid.

Delivery levels found here

• Bare surface-mount sensor: select SHT20 DFN-6 explicitly in mixed SHT20/SHT21/SHT25/HTU21D and SHT30/SHT31/SHT35/SHTC3 menus. Other selected devices can be DFN-4 or DFN-8 and have different pad patterns and command sets. One-, two-, five- and ten-piece quantities appear on different pages. A bare IC does not include a PCB, cable, connector, enclosure or factory-calibrated end-to-end instrument.
• I²C breakout: SHT20 board/module choices include one-, five- and ten-piece selections, some with a short 20 cm or 1 m lead and protective case. Confirm whether a listing's “SHT20 module” contains the sensor or only a compatible PCB. One mixed ten-piece base-plate menu labels A as an empty SHT20 base plate, B as an empty SHT30 plate, and C/D/E as populated modules: empty PCB is not a measuring instrument. Verify pin labels, supply and included pull-ups.
• Cabled probe: selected SHT20 stainless, polymer, PE, PVC and other housing choices offer approximately 30 cm, 1 m, 2 m or 3 m lengths. Some menus combine model, sheath design, housing geometry and “with XH2.54 terminal” versus bare wires. A 3.0 mm metal head and a G1/2-thread probe have different mounting needs; a 30 mm and a 150 mm threaded tube do not fit the same clearance. A 1-, 5- or 10-piece pack option is separate from cable length. Check both the chosen sensor family and mechanical option before specifying a replacement.
• RS485 transmitter: XY-MD02 and other SHT20 temperature/humidity transmitters offer board-only, board-with-shell, “sht20,” “sht20 with case,” circuit-board and enclosed selections. These provide a serial instrument output, often described as Modbus RTU, not a bare I²C sensor connection. Check DC supply, register map, serial settings, terminal wiring and enclosure choice for the exact selected device; an RS485 interface may require a suitable transceiver on the controller.
• Finished controller: W3005 digital humidistats appear as 12 V, 24 V or AC 110–220 V variants, and an AC DTC3200 temperature/humidity controller is also listed. These are controllers with their own display, outputs and safety considerations, not small SHT20 GPIO modules. Match the actual supply variant and load rating to its dedicated documentation; no general mains-wiring procedure is implied by a sensor listing.

SHT20 is not every SHT or AHT model

Mixed chip menus offer SHT20, SHT21 and SHT25 alongside SHT30/31/35 and newer SHT40/41/45. A family resemblance is not proof of identical voltage tolerance, addresses, command bytes, heater functions, conversion times, measurement ranges or package footprints. Some options say “SHT10 replacement,” “SHT11 replacement” or “SHT15 replacement”; a replacement-position product must still be verified electrically and in firmware for the older sensor's nonstandard interface. One listing explicitly offers “Waterproof Membrane,” “Temperature” and “Temperature Humidity” as different product choices. A membrane-only selection is not an electronic probe.

AHT10/AHT20/AHT21/AHT30 boards are separate digital temperature/humidity devices. A title saying “replace SHT20” or “compatible” may describe an application alternative, not a pin-for-pin, address-for-address or software drop-in. Likewise HTU21D, HDC1080, Si7021, SHTC3 and AM2320 use their own specifications and host commands. A mixed “AHT20 Sensor” versus “AHT20 Module” menu even changes the assembly level. Select by full model, required supply and host driver; do not install an SHT20-only library for a DHT22 or assume a sensor returned by an I²C scanner is an SHT20.

DHT11, DHT22/AM2302, AM2301 and related options dominate some listings in this collection. DHT-style sensors use a timed single-data-wire protocol rather than the SHT20 I²C command interface. ESP-01/ESP-01S or D1 mini variant menus also sell only host boards, relays, LED boards, battery shields, buttons, displays or DHT/DS18B20/SHT30 add-ons. Choosing a D1 mini shield does not inherently supply a controller or an SHT20. “DHT22 with ESP8266” versus “DHT22 board” are different deliveries. These products remain visible but must not be described as SHT20 probes.

Electrical and firmware design checks

For a direct I²C SHT20 board, confirm the chosen assembly's supply rail and SDA/SCL logic levels. A chip supply figure is not necessarily the allowed voltage at a breakout's external connector; the board may add a regulator or level conversion, or it may not. Some probe listings specifically call for around 3.3 V and warn against 5 V. Pull-ups on SDA and SCL should connect to a safe rail for every device on the bus. If several breakouts already carry pull-ups, parallel resistances may be too strong; if none do, the bus may fail. Compare the actual connector's pin order, including HY2.0-4P and XH2.54 versions, before mating a cable merely because its shell fits.

Firmware should use the selected device's command set and conversion timing and read both temperature and relative humidity correctly. Detect communication failure and stale results, and allow stabilization following power-up or a large humidity change. A long 1–3 m cabled I²C probe is more sensitive to bus capacitance, cable topology, pull-up choice and electrical noise than a short PCB connection. The offered cable length is not proof that every controller will communicate reliably at its maximum clock rate. Assess the completed harness at installation temperature and under nearby switching activity.

For an RS485/Modbus transmitter, I²C wiring and libraries are not appropriate at the host end. Confirm device address, baud rate, serial framing, register scaling and supply for the selected transmitter; check whether the supplied housing is included. RS485 is the electrical layer, while Modbus RTU is a particular protocol. A listing that says “analog signal” in a generic title should not override the selected instrument's actual register/output documentation. Keep an interface diagram for the chosen product rather than using a generic SHT20 pinout on a powered RS485 board.

Humidity measurement and environmental limits

Position the sensing surface away from heaters, direct sunlight and condensing walls if the aim is room-air humidity. A sealed or tightly meshed protective tip may delay airflow and make the response slower, especially after condensation. Check material and cable temperature limits before installing in a hot chamber. Ambient 100%RH capability as a measurement expression is not a license for liquid submersion or saturated operation indefinitely. For greenhouse or high-humidity use, provide appropriate splash and condensation management and validate recovery and drift over the service interval.

Compare a sensor with a suitable temperature and humidity reference at the operating conditions of interest. Different sensing technologies can agree near room temperature but diverge at extremes or after contamination. Accuracy figures from an individual IC do not include cable failure, enclosure gradient, ADC/control logic, display rounding or sensor-placement error. When a humidistat or thermostat controls critical equipment, design independent fault detection and protective limits rather than depending on a single reading.

Keep unrelated matches separate

One multiprobe menu offers BMP180/BMP280, BME280, SGP30/SGP40 and AHT10 as separate variants alongside SHT20. BMP devices and gas-related SGP devices do not measure the same quantities as an SHT20 simply because they share a probe catalog page. The final pages of this collection also include WSP2110 VOC and MR007 methane/propane gas sensors, which are gas-detection products, not temperature/humidity sensors. Their presence here is not a claim of SHT20 functionality. No products are removed or relabeled by this description; check the selected model and its own specification before purchase.

Ordering checklist

1. Choose the selected SHT20 model, not merely a title naming it alongside SHT30, SHT40, HTU21D, AHT10 or DHT22.
2. Identify the delivery level: bare DFN IC, populated breakout, empty PCB, cable probe, RS485 transmitter, standalone controller or accessory.
3. Confirm humidity and temperature are both available on the chosen option, and verify supply, interface, connector pinout, cable length and pack quantity.
4. Use the exact part's software commands and electrical limits; I²C, DHT single-wire and RS485 Modbus are different integration paths.
5. Review the assembled probe's environmental and mounting limits. “Waterproof,” “high precision” and “replace” are not universal compatibility or certification guarantees.

Selection by actual model, host interface and exposed sensing environment produces a more dependable system than selection by a broad product-page keyword.