SHT20 Industrial Temperature & Humidity Sensor
User Manual

Model: TH-SHT20-4-20mA | Sensor Chip: SHT20 (Sensirion, Switzerland) | Output Signal: 4-20mA | Power Supply: 5.0~9 VDC

1. Product Overview

This sensor uses the high-precision digital temperature and humidity chip SHT20 from Sensirion, Switzerland. It linearly converts temperature and humidity data into a 4-20mA industrial standard analog signal, which can be directly connected to PLCs, DCS systems, digital meters, or data acquisition cards. It is suitable for low-voltage power supply (minimum 5V) applications where digital communication is not required, such as clean workshops, pharmaceutical warehouses, agricultural greenhouses, and HVAC terminal units.

Key Advantages High-precision SHT20 chip | 2-wire/3-wire selectable | Wide voltage 5-9V supply | Industrial 4-20mA output | Strong anti-interference

2. Technical Specifications

Parameter	Description
Supply Voltage	5.0 ~ 9 VDC (5V or 9V recommended)
Power Consumption	≤ 0.1W (≤ 20mA at 5V)
Output Signal	4-20mA (Analog, 2-wire/3-wire selectable, default 3-wire)
Load Resistance	≤ 250Ω @ 5V; ≤ 500Ω @ 9V
Temperature Measurement Range	-40℃ ~ +125℃ (customizable range, see section 6)
Temperature Accuracy	±0.3℃ (typical @ 25℃)
Humidity Measurement Range	0~100% RH (non-condensing)
Humidity Accuracy	±3% RH (typical @ 25℃, 20~80%RH)
Output Mapping	4mA = range lower limit, 20mA = range upper limit (independent for temperature/humidity)
Response Time	≤ 2s (data refresh)
Operating Environment	-40℃ ~ +85℃, 0~99%RH (non-condensing)
Enclosure Protection	Plastic / Aluminum alloy optional (default IP54, IP65 customizable)
Dimensions	Approx. 85×40×30mm (excluding probe/terminal)

3. Wiring Instructions

This sensor supports both 2-wire and 3-wire connections; default is 3-wire.

3.1 3-Wire Connection (Recommended)

Wire Color / Terminal	Description	Connection Target
Red (VCC)	Power Positive	Connect to 5~9V DC Positive
Black (GND)	Power Negative / Signal Ground	Connect to Power Negative and DAQ GND
Yellow (OUT)	4-20mA Current Output	Connect to DAQ AI+ (Current Input Channel)

3.2 2-Wire Connection (Requires Customization)

Power and signal share two wires:

Red wire → Connect to DAQ AI+ (provides power simultaneously)
Black wire → Connect to Power Negative and DAQ AI-

📌 Note: For 2-wire connection, a load resistor (typically 250Ω, sampling voltage 1-5V) must be inserted in the DAQ loop. Ensure that the voltage drop across the load resistor plus the sensor's minimum operating voltage is ≤ the supply voltage.

4. Current to Temperature/Humidity Relationship

Default factory range:

Temperature: -40℃ ~ +125℃ (corresponding to 4-20mA)
Humidity: 0~100% RH (corresponding to 4-20mA)

Calculation Formula

Temperature (℃) = (I - 4) / 16 × (T_max - T_min) + T_min
Example: Range -40~125℃, measured 12mA:
(12-4)/16 × (125 - (-40)) + (-40) = 0.5 × 165 - 40 = 42.5℃

Humidity (%RH) = (I - 4) / 16 × 100
Example: measured 12mA → (12-4)/16 × 100 = 50.0%RH

Custom Range (Factory Set)

Order Code	Temperature Range	Humidity Range
Default	-40~125℃	0~100%RH
T1	0~50℃	0~100%RH
T2	-20~80℃	0~100%RH
T3	Custom according to customer requirements

If you need to modify the range, please specify when ordering. It cannot be changed on-site after delivery (requires a dedicated programmer).

5. Usage Steps

Wiring: Connect the sensor to the power supply and acquisition device according to 3-wire or 2-wire configuration.
Power On: Allow the sensor to warm up for 3 minutes for stable output.
Current Reading: Read the 4-20mA value using an ammeter or PLC analog input module.
Conversion: Calculate the actual temperature and humidity using the range formula.
Fault Diagnosis: Output < 4mA → Sensor power failure or damaged; Output > 20mA → Out of range or sensor fault.

6. Precautions

⚠️ Important Safety and Usage Instructions:
1️⃣ Power Supply Requirements: Supply voltage must never exceed 9V DC, otherwise internal circuits may be damaged.
2️⃣ Load Resistance: For 3-wire connection, load ≤ 250Ω @ 5V; if using higher voltage (e.g., 9V), load can be increased up to ≤ 500Ω.
3️⃣ Signal Isolation: For long-distance transmission (>50m), use shielded cable and avoid running parallel to power cables.
4️⃣ Condensation Prevention: The SHT20 chip should not be exposed to high-humidity condensing environments for long periods, as it may cause drift.
5️⃣ Calibration: Factory calibrated; user calibration is not required on-site.

7. Troubleshooting

Issue	Possible Cause	Solution
No current output (0mA)	Power disconnected, wiring error	Check voltage between VCC and GND
Output 3.8~4.0mA	Sensor not warmed up or low temperature environment	Warm up for 3 minutes, or check if temperature is below lower limit
Output >20mA and constant	Sensor chip damaged	Replace sensor
Output fluctuates severely	Electromagnetic interference, poor grounding	Use shielded cable, single-point grounding
Significant accuracy deviation	Out of range or condensation	Restore to normal temperature dry environment, retest

8. Package Contents

Temperature & Humidity Sensor Unit ×1
Waterproof Connector (Optional) ×1
Factory Test Report ×1
Certificate of Conformity ×1

9. Ordering Information

Model Code	Output Type	Power Supply	Temperature Range	Humidity Range
YTL-SHT20-420-5-9	4-20mA (3-wire)	5-9V	-40~125℃	0~100%RH
Customizable 2-wire or special ranges; please add suffix to model number.

10. Technical Support

For custom ranges, 2-wire versions, or technical inquiries, please contact the manufacturer.

SHT20 Industrial Temperature & Humidity SensorUser Manual