Sensirion SHT4xI Sensor Calibration Use Case

Example demonstrating real-time output uncertainty estimation for calibrated ADC values from the SHT4xI sensor¹.

Introduction

The SHT4xI is a humidity and temperature sensor IC¹.

Getting started

The correct way to clone this repository to get the submodules is:

	git clone --recursive [email protected]:signaloid/Signaloid-Demo-Sensors-SensirionSHT4xIConversionRoutines.git

If you forgot to clone with --recursive and end up with empty submodule directories, you can remedy this with:

	git submodule update --init

Running the application locally

Apart from using Signaloid's Cloud Compute Platform, you can compile and run this application locally. Local execution is essentially a native Monte Carlo implementation, that uses GNU Scientific Library (GSL)² to generate samples for the different input distributions. In this mode the application stores the generated output samples, in a file called data.out. The first line of data.out contains the execution time of the Monte Carlo implementation in microseconds (μs), and each next line contains a floating-point value corresponding to an output sample value. Please note, that for the Monte Carlo output mode, you need to select a single output to calculate, using (-S) command-line option.

In order to compile and run this application in the native Monte Carlo mode:

0. Install dependencies (e.g., on Linux):

sudo apt-get install libgsl-dev libgslcblas0

1. Compile natively (e.g., on Linux):

cd src/
gcc -I. -I/opt/local/include main.c utilities.c common.c uxhw.c -L/opt/local/lib -o native-exe -lgsl -lgslcblas -lm

2. Run the application in the MonteCarlo mode, using (-M) command-line option:

./native-exe -M 10000 -S 0

The above program runs 10000 Monte Carlo iterations, calculating the output chosen by (-S 0) command-line option. 3. See the output samples generated by the local Monte Carlo execution:

cat data.out

Inputs

The inputs to the SHT4xI sensor conversion algorithms are the ratiometric analog voltage output of the sensor for the relative humidity measurement in Volts($V_{RH}$), the ratiometric analog voltage output of the sensor for the temperature measurement in Volts ($V_{T}$), as well as the Supply voltage of the sensor ($V_{dd}$). The algorithm models the uncertainty in the analog output as well as in the supply voltage using uniform distributions.

The uncertainty in $V_{RH}$ is modeled as a (UniformDist(2.3, 2.7)) Volts.

The uncertainty in $V_{T}$ is modeled as a (UniformDist(2.3, 2.7)) Volts.

The uncertainty in $V_{dd}$ is modeled as a (UniformDist(4.8, 5.4)) Volts.

Outputs

The output can be the calibrated relative humidity in percentage, the calibrated temperatrue in Celsius or in Farenheit. Select between the different outputs using the -S command-line parameter:

• -S 0: Calculates the Relative Humidity, given by

$$\mathrm{RH} = -12.5 + 125 * \frac{V_{RH}}{V_{dd}}$$

Following is an example output, using Signaloid's C0Pro-S core:

• -S 1: Calculates the Temperature in Celcius, given by

$$\mathrm{Temperature_Celsius} = -66.875 + 218.75 * \frac{V_{T}}{V_{dd}}$$

Following is an example output, using Signaloid's C0Pro-S core:

• -S 2: Calculates Temperature in Fahrenheit, given by

$$\mathrm{Temperature_Farenheit} = -88.375 + 393.75 * \frac{V_{T}}{V_{dd}}$$

Following is an example output, using Signaloid's C0Pro-S core:

• -S 3: Calculates all previous calibrated outputs. Selected by default.

Usage

Example: SHT4xI sensor conversion routines - Signaloid version

Usage: Valid command-line arguments are:
	[-o, --output <Path to output CSV file : str>] (Specify the output file.)
	[-S, --select-output <output : int>] (Compute 0-indexed output. Calculate all possible outputs if equal to 3. Default value: 3.)
	[-M, --multiple-executions <Number of executions : int (Default: 1)>] (Repeated execute kernel for benchmarking.)
	[-T, --time] (Timing mode: Times and prints the timing of the kernel execution.)
	[-b, --benchmarking] (Benchmarking mode: Generate outputs in format for benchmarking.)
	[-j, --json] (Print output in JSON format.)
	[-h, --help] (Display this help message.)

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Footnotes

1. SHT4xI Humidity and Temperature Sensor IC. ↩ ↩²

2. GNU Scientific Library. ↩