TFHT01 - UAV Humidity and Temperature Sensor

The TFHT01 hygrometer sensor can be directly connected to a Pixhawk autopilot with PX4 firmware, or it can be used as a sensor for the TF-ATMON monitoring system.

Sensors mounted on UAVs can be used for a variety of purposes. TFHT01 can measure air temperature and humidity, which can be used for meteorological purposes to estimate whether icing may form on aerodynamic surfaces. It could also be used to determine if the flight is conducted within the operating range of the drone. Another use can be to measure the temperature of selected UAV components, for example, the temperature of batteries, ESC, motor, or some bearings.

Where to get it?

TFHT01 can be bought directly from us via our contact email. The email can also be used if there are specific requirements for custom modifications or if the product will be inquired in large quantities. TFHT01 is also available for online purchase through the Tindie store.

Parameters

Parameter	Value	Description
Sensing element	SHT35	Other possible sensors are SHT30 or SHT31
Typical accuracy	1.5 %RH and 0.1 °C
Repeatability	0.15 %RH , 0.08 °C	The stated repeatability is 3 times the standard deviation (3σ) of multiple consecutive measurements at constant ambient conditions.
Operating temperature range	0 °C - +65 °C	Sensor physically measures in range -40°C to +120°C with reduced accuracy
Operating humidity range	0-100 %	At humidity above 80% the performance of the sensor could be degraded in case of prolonged periods
I2C connector	4-pin JST-GH	The second connector could be installed on the opposite side
I2C address	0x44 default	By switching of JP1 is possible change address to 0x45
Storage temperature range	-20 °C - +40 °C
Operational input voltage	3.6 - 5.4V	Overvoltage internally protected by zener diode
Mass	2 g	PCB without cabling
Dimensions	30 x 15 x 6.5 mm	PCB
Weather resistance	IP40	External connectors fully occupied. The sensor itself could be protected by IP67 according the sensirion datasheet

Applications

Atmospheric sounding

The TFHT01 sensor could be used for direct atmospheric sounding. Here is an example of measured data taken by TF-G2 autogyro.

Schematics

Usage in PX4 autopilot firmware

The PX4 autopilot firmware supports the sensor. Multiple sensors can be connected to one autopilot. The measured data are immediately sent to the ground station and they are also logged in the onboard ulog file. Sensor support can be enabled by setting the SENS_EN_SHT3X parameter to 1.

Driver Commands Examples

CLI usage example:

sht3x start -X

Start the sensor driver on the external bus

sht3x status

Print driver status

sht3x values

Print the last measured values

sht3x reset

Reinitialize senzor, reset flags

PX4 Driver Usage

sht3x <command> [arguments...]
 Commands:
   start
     [-I]        Internal I2C bus(es)
     [-X]        External I2C bus(es)
     [-b <val>]  board-specific bus (default=all) (external SPI: n-th bus
                 (default=1))
     [-f <val>]  bus frequency in kHz
     [-q]        quiet startup (no message if no device found)
     [-a <val>]  I2C address
                 default: 68
     [-k]        If initialization (probing) fails, keep retrying periodically

   stop

   status        print status info

   values        Print actual data

   reset         Reinitialize sensor

Usage in Ardupilot firmware

In the Ardupilot firmware, the corresponding sht3x driver for TFHT01 is currently missing. The contributions are welcomed.

FAQ

I am not able to find the SENS_EN_SHT3X parameter in QGC

Unfortunately, the PX4 developers have disabled the compilation of the TFHT01 sensor driver in the default release versions of the firmware due to memory constraints of the autopilot hardware. To compile the driver, you must modify the Kconfig configuration using the boardconfig tool (make px4_fmu-v5_default boardconfig). Please follow the instructions on PX4 menuconfig setup In the configuration tree, locate Drivers -> Hygrometers and enable HYGROMETER SHT3x. After setting up the firmware with these changes, compile it and upload it to your autopilot. Then you should see the SENS_EN_SHT3x parameter.