Attributes

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

6 reviews

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.

5 FAQ

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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