Description
Reviews
| Brand | - |
| Category | Robotics / STEM Teaching Tools / Sensors |
| Origin | - |
| Model Number | CJ-HJ31A |
| Replacement For | HR202L |
| Sensor Type | Humidity Sensitive Resistor |
| Operating Voltage | DC 3.3V - 5V |
| Response Time | < 10 seconds |
| Humidity Range | 20% - 90% RH |
| Package Type | Surface Mount Device (SMD) |
| Operating Temperature | -10°C to +60°C |
| Accuracy | ±5% RH |
| Application | Home Automation, Weather Stations |
Anonymous
Mar 29, 2026
Rating: 4/5
Solid performance
No complaints about performance. It reads consistently and replaces the older model without any circuit modifications. Deducting one star only because the delivery took longer than expected.
Anonymous
Mar 19, 2026
Rating: 5/5
Perfect drop-in replacement
I needed a replacement for an old HR202L sensor in my weather station project. This CJ-HJ31A fit perfectly and started reading humidity levels immediately after calibration. Great value for the price.
Anonymous
Mar 12, 2026
Rating: 4/5
Good sensitivity, requires calibration
The sensor is quite sensitive to changes in humidity. Just remember that like most resistive sensors, it needs a bit of calibration against a known standard to get accurate readings. Works well for DIY projects.
Anonymous
Mar 06, 2026
Rating: 5/5
Excellent for Arduino projects
Very easy to interface with an Arduino or ESP32. The resistance curve is consistent with the datasheet. I've used these in several student projects and they hold up well to handling.
Anonymous
Mar 05, 2026
Rating: 3/5
Works but packaging was poor
The sensor itself functions as expected and matches the specs for the HR202L. However, two of the five units I ordered arrived with bent pins due to insufficient packaging. The working ones are fine though.
Anonymous
Mar 02, 2026
Rating: 5/5
Reliable for greenhouse monitoring
Using these in a small automated greenhouse setup. They have been running for three months without drift issues. The response time is fast enough to trigger my misting system effectively.
Q: Does this come with a breakout board or just the chip?
A: This listing is for the SMD sensor chip only. You will need to solder it to your own PCB or a generic breakout board for testing.
Q: What is the expected lifespan of this sensor in continuous use?
A: Under normal operating conditions within the specified temperature and humidity ranges, the sensor typically lasts for several years. Exposure to corrosive gases or extreme condensation may reduce lifespan.
Q: Is this sensor compatible with 3.3V logic levels?
A: Yes, the CJ-HJ31A operates comfortably within the 3.3V to 5V DC range, making it suitable for both 3.3V and 5V microcontroller systems.
Q: Is there a calibration procedure recommended?
A: We recommend comparing the sensor output against a calibrated reference hygrometer in a controlled environment and adjusting your code's conversion formula accordingly for best results.
Q: Can I use this to measure relative humidity above 90%?
A: While the sensor may physically survive higher humidity, its accuracy and linearity are guaranteed only up to 90% RH. Prolonged exposure to near-saturation levels can cause temporary drift.
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