Attributes

Brand	-
Category	Robotics / STEM Teaching Tools / Sensors
Origin	-
Model Number	CJ-HJ31A / HR202L
Sensor Type	Resistive Humidity Sensor
Operating Voltage	DC 1.5V - 5V
Humidity Range	20% RH to 90% RH
Response Time	< 10 seconds
Recovery Time	< 30 seconds
Accuracy	±5% RH (at 25°C)
Package Style	Through-hole / Module
Operating Temperature	-10°C to +50°C
Application	Home Automation, Weather Stations

6 reviews

Anonymous

Mar 29, 2026

Rating: 3/5

Works well but fragile

The sensing element itself is a bit delicate. One of my units stopped working after I accidentally touched the grid with a probe too hard. Functionality is good if handled with care.

Anonymous

Mar 26, 2026

Rating: 5/5

Perfect for my Arduino project

This sensor worked exactly as expected. The resistance changes smoothly with humidity levels, and it was very easy to interface with my microcontroller. Great value for the price.

Anonymous

Mar 26, 2026

Rating: 5/5

Easy to use for beginners

As someone new to electronics, I found this module very forgiving. The pins are clearly labeled, and there are plenty of tutorials online for the HR202L chip. Highly recommended.

Anonymous

Mar 25, 2026

Rating: 4/5

Solid performance

The build quality is decent for the cost. It responds quickly to changes in humidity, like when I breathe on it or use a humidifier. Just make sure not to expose it to direct water droplets.

Anonymous

Mar 20, 2026

Rating: 4/5

Good sensitivity, needs calibration

I am using this to monitor soil moisture indirectly via air humidity in my greenhouse. It is quite sensitive, but you definitely need to calibrate it against a known standard for precise readings.

Anonymous

Mar 18, 2026

Rating: 5/5

Reliable for long-term logging

I have had three of these running in a data logger setup for two months now. They have remained stable and consistent. No drift issues observed so far.

5 FAQ

Q: Can this sensor be used directly underwater?

A: No, this is a humidity sensor designed to measure moisture in the air. Submerging it in water will likely damage the resistive element permanently.

Q: Is the black and white color difference significant?

A: No, the color variation (black or white substrate) depends on the manufacturing batch and does not affect the electrical performance or specifications of the sensor.

Q: What is the typical lifespan of this sensor?

A: Under normal operating conditions within the specified temperature and humidity ranges, these sensors typically last for several years. Exposure to extreme conditions or corrosive gases may reduce lifespan.

Q: Does this come with a library for Raspberry Pi?

A: Since this is a raw analog component, there is no specific 'driver' library. However, you can easily read it using Python with the GPIO Zero or RPi.GPIO libraries by reading the analog pin via an external ADC chip like the MCP3008.

Q: What is the output signal type?

A: This is a resistive sensor. The output is a change in resistance based on humidity levels. You will need to use a voltage divider circuit and an ADC (Analog-to-Digital Converter) on your microcontroller to read the value.

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