README.md
Source code
[](https://doi.org/10.5281/zenodo.6338378)
# T9602_Library
***Arduino library interface for the [Telaire T9602 humidity and temperature sensor](https://www.amphenol-sensors.com/en/telaire/humidity/527-humidity-sensors/3224-t9602)***
***T9602 sensor.*** *Image from Amphenol/Telaire (see link above).*
## Library
**Full API reference:** https://docs.northernwidget.com/T9602_Library/ (Doxygen, built from `master` by GitHub Actions).
## Key sensor features
* IP67 rated
* -20 to 70 °C operating range
* Accuracy
* ±2% RH, 0-95% RH
* ±0.5°C
* 14 bit resolution
[Data sheet](https://www.amphenol-sensors.com/en/component/edocman/304-telaire-t9602-humidity-temperature-sensor-datasheet/download?Itemid=8487%20%27) for the full T9602 series.
[Application guide for the ChipCap® 2 Humidity and Temperature Sensor](https://www.amphenol-sensors.com/en/component/edocman/397-telaire-chipcap2-humidity-and-temperature-sensor-application-guide/download?Itemid=8487%20%27) (core unit within the T9602). Importantly, this includes a guide to the I2C bus. This library operates only using the default I2C address (0x28), so you will need to consult this and this library (and make a pull request, please!) if you want to allow for different addresses to be set/used.
## Sensor options
Our two most commonly used sensors are:
* [T9602-3-D](https://www.digikey.com/product-detail/en/amphenol-advanced-sensors/T9602-3-D/235-1563-ND/5027914)
* I2C
* 3.3V
* 1.8 m cable
* [T9602-3-D-1](https://www.digikey.com/product-detail/en/amphenol-advanced-sensors/T9602-3-D-1/235-1377-ND/5027895)
* I2C
* 3.3V
* 1.0 m cable
5V versions, as well as those with other communications protocols, [are available as well](https://www.digikey.com/products/en/sensors-transducers/humidity-moisture-sensors/529?k=t9602).
## Wiring
**_WARNING_: LAYOUT DIFFERS FROM OUR STANDARD CONVENTIONS**
| **Color** | **Connection** |
|-----------|----------------|
| Red | V+ |
| Green | GND |
| White | SDA |
| Black | SCL |
We typically snip off the connector at and wire the sensor directly into the screw terminals of our data logger ([Resnik](https://github.com/NorthernWidget-Skunkworks/Project-Resnik) or [Margay](https://github.com/NorthernWidget-Skunkworks/Project-Margay)) or into our [Heptapod](https://github.com/NorthernWidget-Skunkworks/Project-Heptapod/) I2C expander. You may instead choose to find a mating plug; the wires feel a bit delicate, but in our experience hold up better than expected.
***T9602 and connector.*** *Image from Digi-Key (see links above).*
## Writing a program to connect to the T9602
You should be able to use any standard Arduino device to connect to the T9602 and read its data.
*This code is untested. If you do test it, please confirm that it works and/or create a PR and/or an issue for it to be fixed.*
### Very simple Arduino code
This code is intended for any generic Arduino system. It is not proven.
```c++
// Include the T9602 library
#include "T9602.h"
// Instantiate class
T9602 mySensor;
void setup(){
// Begin Serial connection to computer at 38400 baud
Serial.begin(38400);
// Print the header just once, straight to the port
mySensor.printDataHeader(Serial);
Serial.println();
}
void loop(){
// Take one reading every (10 + time to take reading) seconds
// and print it to the screen
mySensor.updateMeasurements();
mySensor.printDataRow(Serial);
Serial.println();
delay(10000); // Wait 10 seconds before the next reading, inefficiently
}
updateMeasurements() sends a measurement request and then fetches data until the sensor’s status bits report a valid, not-yet-fetched measurement. It returns true on success and false after T9602_TIMEOUT_MS (250 ms by default; define it before the include to change it) without valid data, in which case the stored values are NW_ERROR (-9999). getStatus() returns the last status bits: 0 valid, 1 stale (already fetched since the last measurement cycle), 2 command mode (the sensor is still starting up), 3 no data (no sensor answered). printDataRow(out) prints what the last updateMeasurements() left, and takes no reading of its own, so the same row can go to the card and the monitor without measuring twice. Both it and printDataHeader(out) write into any Print: no row is composed in RAM.
setReadings(n) sets how many readings updateMeasurements() takes (each is its own measurement cycle, so they are independent; clamped to T9602_CAPACITY, default 16, override before the include); the getters then return the means, and getHumidityMean(), getHumidityStd(), getHumiditySterr(), getHumidityMedian(), the same for temperature, and getReadingCount() read the stored readings. With setStats(true) the std and sterr columns join printDataHeader() and printDataRow(). For one row per reading to a file, beginReadings(n), printHeader(out), logReading(out) n times, endReadings(), to any Print (an SdFat File, Serial). Requires the NW_Core library.
Northern Widget Margay code
The Margay data logger is the lightweight and low-power open-source data-logging option from Northern Widget. It saves data to a local SD card and includes on-board status measurements and a low-drift real-time clock. We have written a library to interface with the Margay, which can in turn be used to link the Margay with sensors.
A Margay cannot yet hold a T9602. A logger writes its file from the sensors watch() gave it, and watch() takes an NW_Sensor: a device that names itself in Page 0 and reports through the Schema 1 Report register (LIBRARY-DESIGN.md section 14). The T9602 is an Amphenol part with neither, so this sketch logs the logger’s own on-board columns and prints the T9602’s to the serial monitor; its columns do not reach the card. Read that as the open end of the work rather than as the intended shape.
// Include the T9602 library
#include <Margay.h>
#include <T9602.h>
// Instantiate classes
T9602 mySensor;
Margay Logger(MODEL_2v0, BUILD_B); // Margay v2.2; UPDATE CODE TO INDICATE THIS
//Number of seconds between readings
uint32_t updateRate = 60;
void setup(){
mySensor.begin();
mySensor.printDataHeader(Serial);
Serial.println();
Logger.begin();
}
void loop(){
Logger.run(updateRate);
}
Testing
extras/test/run.sh compiles the library on a desktop against stub Arduino.h and Wire.h that emulate the ChipCap 2 status bits, and checks that the output for fixed sensor behaviour is byte-identical to extras/test/baseline.txt. Run it after any change; --record rewrites the baseline when an output change is intended.
Acknowledgments
Support for this project provided by:
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Updated on 2026-10-04 at 04:51:47 +0000