Sensirion SDP3x-Analog Sensor Calibration Use Case

Example demonstrating real-time output uncertainty estimation for calibrated ADC values from the Sensirion SDP3x-Analog sensor¹.

Introduction

The Sensirion SDP3x-Analog sensor is a differential pressure sensor with analog output. This application demo calculates the calibrated pressure outputs for different variants of the sensor in different configurations.

Getting started

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

	git clone --recursive [email protected]:signaloid/Signaloid-Demo-Sensors-SensirionSDP3xAnalogConversionRoutines.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 SDP3x sensor conversion algorithms are the analog voltage output of the sensor ($A_{out}$) 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 $A_{out}$ is modeled as a (UniformDist(1.3, 1.7)) Volts.

The uncertainty in $V_{dd}$ is modeled as a (UniformDist(3.3, 3.9)) Volts.

Outputs

The output is the calibrated pressure in Pascal. There are two variants of the sensor (SDP36 and SDP37) and each can operate in either a linear mode or with quare root output. See the datasheet¹ for more information. Select between the variants using the -S command-line parameter:

• -S 0: Calculates the calibrated output of SDP36 sensor variant in linear configuration, given by

$$\mathrm{Calibrated Sensor Output} = \frac{750 * A_{out}}{V_{dd}} - 150$$

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

• -S 1: Calculates the calibrated output of SDP37 sensor variant in linear configuration, given by

$$\mathrm{Calibrated Sensor Output} = \frac{190 * A_{out}}{V_{dd}} - 38$$

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

• -S 2: Calculates the calibrated output of SDP36 sensor variant in square root configuration, given by

$$\mathrm{Calibrated Sensor Output} = sign(\frac{A_{out}}{V_{dd}} - 0.5)*{(\frac{A_{out}}{V_{dd} * 0.4} - 1.25)}^2 * 525$$

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

• -S 3: Calculates the calibrated output of SDP37 sensor variant in square root configuration, given by

$$\mathrm{Calibrated Sensor Output} = sign(\frac{A_{out}}{V_{dd}} - 0.5)*{(\frac{A_{out}}{V_{dd} * 0.4} - 1.25)}^2 * 133$$

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

• -S 4: Calculates all previous calibrated outputs. Selected by default.

Usage

Example: SDP3x 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 4. Default value: 4.)
	[-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. Datasheet SDP3x-Analog. ↩ ↩²

2. GNU Scientific Library. ↩