Ambient Light Lux Sensor VEML7700 - Versionsgeschichte

Onyesi-john.abiagam@stud.hshl.de: /* VEML7700 Automatic Gain and Integration Time Selection Across Varying Light Levels */

2026-06-11T12:35:02Z

VEML7700 Automatic Gain and Integration Time Selection Across Varying Light Levels

← Nächstältere Version		Version vom 11. Juni 2026, 12:35 Uhr
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	To observe the behavior of the auto-ranging feature, measurements were taken in the Light Laboratory using a LabRef luxmeter as the reference instrument. For each light level, the corresponding VEML7700 reading and the automatically selected gain and integration time settings were recorded. The results are summarized in Table 2.		To observe the behavior of the auto-ranging feature, measurements were taken in the Light Laboratory using a LabRef luxmeter as the reference instrument. For each light level, the corresponding VEML7700 reading and the automatically selected gain and integration time settings were recorded. The results are summarized in Table 2.

			{\| class="wikitable"
			\|+ '''Table 2. VEML7700 ALS2Lux Calibration Using Corrected Reference Luxmeter Values'''
			! Raw ALS Count
			! Corrected Reference Lux (Lux)
			! Calculated Lux After Calibration (Lux)
			! Gain and Integration Time Configuration
			\|-
			\| 466
			\| 98
			\| 94.02
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 778
			\| 217.5
			\| 217.09
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 1126
			\| 361.6
			\| 361.97
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 1295
			\| 439.7
			\| 435.37
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 1626
			\| 593.3
			\| 585.33
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 1948
			\| 741.4
			\| 738.73
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 2264
			\| 892.8
			\| 896.38
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 2574
			\| 1049.5
			\| 1058.02
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 2727
			\| 1126.7
			\| 1140.17
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 3326
			\| 1430.2
			\| 1477.89
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 5143
			\| 2424.5
			\| 2420.77
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 6171
			\| 3010.7
			\| 3008.41
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 7255
			\| 3663.7
			\| 3673.42
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 7716
			\| 3940.6
			\| 3972.22
			\| Gain = 1/8, IT = 100 ms
			\|-
			\| 8276
			\| 4360.4
			\| 4352.18
			\| Gain = 1/8, IT = 100 ms
			\|}

	{\| class="wikitable"		{\| class="wikitable"

Onyesi-john.abiagam@stud.hshl.de: /* VEML7700 Automatic Gain and Integration Time Selection Across Varying Light Levels */

2026-06-01T14:06:28Z

VEML7700 Automatic Gain and Integration Time Selection Across Varying Light Levels

← Nächstältere Version		Version vom 1. Juni 2026, 14:06 Uhr
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	{\| class="wikitable"		{\| class="wikitable"
	\|+ '''Table 2.This Shows the Automatic Selection and Adjustment of Gain and Integration Time Across Different Reference light Levels Measured Using the LabRef Luxmeter and VEML7700 Sensor'''		\|+ '''Table 2.This Shows the Automatic Selection and Adjustment of Gain and Integration Time Across Different Reference light Levels Measured Using the LabRef Luxmeter and VEML7700 Sensor'''
	! Reference Luxmeter ~~Reading~~		! Reference Luxmeter Value
	! Raw ALS Count		! Raw ALS Count
	! Lux		! Lux

Onyesi-john.abiagam@stud.hshl.de: /* Reference Lux Meter Reading vs LX-1108 Measurement */

2026-05-31T17:35:34Z

Reference Lux Meter Reading vs LX-1108 Measurement

← Nächstältere Version		Version vom 31. Mai 2026, 17:35 Uhr
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	* The observed deviation between the two instruments suggests that the relationship cannot be adequately represented by a single constant correction factor.		* The observed deviation between the two instruments suggests that the relationship cannot be adequately represented by a single constant correction factor.

	'''Note:''' The analysis presented ~~in this report~~ is specific to ~~the~~ LX-1108 lux meter used during the experiment and should not be generalized to Ambient Light Sensors (ALS) or other light-sensing devices, as different devices exhibit different measurement characteristics and require independent calibration procedures.		'''Note:''' The analysis presented here is specific to Lab Reference lux meter and LX-1108 lux meter.

	=== Table 1: Reference Lux Meter and LX-1108 Measurement Data ===		=== Table 1: Reference Lux Meter and LX-1108 Measurement Data ===
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	* The varying deviation suggests that a nonlinear model is required to accurately characterize the relationship.		* The varying deviation suggests that a nonlinear model is required to accurately characterize the relationship.
	* Consequently, nonlinear regression was employed to establish a calibration model for the LX-1108.		* Consequently, nonlinear regression was employed to establish a calibration model for the LX-1108.

	== Relative Error Before Calibration ==		== Relative Error Before Calibration ==

Onyesi-john.abiagam@stud.hshl.de: /* VEML7700 Automatic Gain and Integration Time Adjustment Procedure (Vishay Datasheet) */

2026-05-31T12:54:10Z

VEML7700 Automatic Gain and Integration Time Adjustment Procedure (Vishay Datasheet)

← Nächstältere Version		Version vom 31. Mai 2026, 12:54 Uhr
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	* Apply the correction formula for high light levels when required to compensate for sensor non-linearity.		* Apply the correction formula for high light levels when required to compensate for sensor non-linearity.

	A detailed flowchart of the complete auto-ranging procedure is provided in the Vishay application note.		A detailed flowchart of the complete auto-ranging procedure is provided in the Vishay application note datasheet( see link at the end of the page).

	= Measurement Circuit =		= Measurement Circuit =

Onyesi-john.abiagam@stud.hshl.de: /* Datasheets */

2026-05-31T12:52:09Z

Datasheets

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	= Video =		= Video =

	~~= Datasheets =~~

			== Datasheets ==

			* [https://www.vishay.com/docs/84286/veml7700.pdf VEML7700 Datasheet]

			* [https://www.vishay.com/docs/84323/designingveml7700.pdf Designing the VEML7700 Into an Application (Application Note)]
	----		----
	→ back to main article: [[:Category:Sensors\|Sensor Kit]]<br>		→ back to main article: [[:Category:Sensors\|Sensor Kit]]<br>

Onyesi-john.abiagam@stud.hshl.de: /* Measurement Method */

2026-05-31T12:43:43Z

Measurement Method

Änderungen zeigen

Onyesi-john.abiagam@stud.hshl.de: /* Measurement Method */

2026-05-31T05:16:22Z

Measurement Method

← Nächstältere Version		Version vom 31. Mai 2026, 05:16 Uhr
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	* Measurements were obtained simultaneously using the laboratory reference lux meter and the LX-1108 lux meter.		* Measurements were obtained simultaneously using the laboratory reference lux meter and the LX-1108 lux meter.
	* The laboratory reference lux meter served as the reference instrument, while the LX-1108 was treated as the instrument under investigation.		* The laboratory reference lux meter served as the reference instrument, while the LX-1108 was treated as the instrument under investigation.
	* The relationship between the two instruments was examined over the selected ~~illuminance~~ range.		* The relationship between the two instruments was examined over the selected light range.
	* Table 1 presents the recorded measurements obtained from both instruments.		* Table 1 presents the recorded measurements obtained from both instruments.
	* Figure 1 shows the corresponding LX-1108 measurements plotted against the reference lux meter readings.		* Figure 1 shows the corresponding LX-1108 measurements plotted against the reference lux meter readings.
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	[[Datei:Error_before.png\|center\|thumb\|800px\|Figure 2: Relative Error Before Calibration.]]		[[Datei:Error_before.png\|center\|thumb\|800px\|Figure 2: Relative Error Before Calibration.]]

	* The LX-1108 ~~exhibited~~ a ~~systematic~~ deviation relative to the laboratory reference lux meter.		* The LX-1108 showed a deviation relative to the laboratory reference lux meter.
	* The relative error remained approximately within the range of 20% to 28% over the measurement range.
	* The error was not constant and generally increased at higher illuminance levels.		* The error was not constant and generally increased at higher illuminance levels.
	* The varying error indicates that a single constant scaling factor would not adequately compensate for the observed deviation.		* The varying error indicates that a single constant scaling factor would not adequately compensate for the observed deviation.
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	The results presented in Figure 1 and Figure 2 indicate that the LX-1108 exhibits a systematic and non-uniform deviation relative to the laboratory reference lux meter. Furthermore, the relative error varies across the measurement range, suggesting that the relationship between the two instruments cannot be adequately described using a single constant scaling factor.		The results presented in Figure 1 and Figure 2 indicate that the LX-1108 exhibits a systematic and non-uniform deviation relative to the laboratory reference lux meter. Furthermore, the relative error varies across the measurement range, suggesting that the relationship between the two instruments cannot be adequately described using a single constant scaling factor.

	To mathematically characterize this relationship, a nonlinear regression model was developed using the experimental measurement data. The laboratory reference lux meter readings (LabRef) were treated as the independent variable, while the corresponding LX-1108 measurements (~~LXReading~~) were treated as the dependent variable.		To mathematically characterize this relationship, a nonlinear regression model was developed using the experimental measurement data. The laboratory reference lux meter readings (LabRef) were treated as the independent variable, while the corresponding LX-1108 measurements (LX_Reading) were treated as the dependent variable.

	A power-law regression model was selected and expressed as:		A power-law regression model was selected and expressed as:
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	* The red curve represents the fitted nonlinear regression model.		* The red curve represents the fitted nonlinear regression model.
	* The dashed black line represents the ideal relationship (<math>y=x</math>) between the two instruments.		* The dashed black line represents the ideal relationship (<math>y=x</math>) between the two instruments.
	* The regression curve closely follows the experimental measurements throughout the calibration range.		* The fitted model captures the deviation of the LX-1108 relative to the laboratory reference lux meter.
	* The fitted model captures the ~~systematic~~ deviation of the LX-1108 relative to the laboratory reference lux meter.
	* The resulting regression equation provides the mathematical basis for deriving a calibration function for the LX-1108.		* The resulting regression equation provides the mathematical basis for deriving a calibration function for the LX-1108.

			== Derivation of the TrueLux Function ==

			Using the nonlinear regression model derived in the previous section, an inverse function was established to estimate the corresponding reference luxmeter value from a measured LX-1108 reading.

			The resulting inverse relationship is:

			<math>
			TrueLux =
			\left(
			\frac{MeasuredLux}{1.428934}
			\right)^{\frac{1}{0.932233}}
			</math>

			Defining this inverse relationship as:

			<math>
			Lux2Ref(MeasuredLux)
			</math>

			the function can be expressed as:

			<math>
			TrueLux = Lux2Ref(MeasuredLux)
			</math>

			where:

			* <math>MeasuredLux</math> is the measured LX-1108 reading.
			* <math>Lux2Ref()</math> is the calibration function derived from the nonlinear regression model.
			* <math>TrueLux</math> is the estimated reference lux value.


	== Calibration of LX-1108 Measurements ==		== Calibration of LX-1108 Measurements ==

	The nonlinear regression model was used to establish a calibration function capable of estimating the corresponding reference ~~illuminance~~ value from a measured LX-1108 reading.		The nonlinear regression model was used to establish a calibration function capable of estimating the corresponding reference lux value from a measured LX-1108 reading.

	The calibration function was subsequently applied to the LX-1108 measurements to obtain corrected ~~illuminance~~ values.		The calibration function was subsequently applied to the LX-1108 measurements to obtain corrected Lux values.

	[[Datei:Corrected LXReading.png\|center\|thumb\|800px\|Figure 4: Corrected LX-1108 measurements compared with the laboratory reference lux meter readings.]]		[[Datei:Corrected LXReading.png\|center\|thumb\|800px\|Figure 4: Corrected LX-1108 measurements compared with the laboratory reference lux meter readings.]]
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	* The systematic deviation observed in the raw LX-1108 measurements has been substantially reduced.		* The systematic deviation observed in the raw LX-1108 measurements has been substantially reduced.
	* The corrected values exhibit improved agreement with the laboratory reference lux meter readings.		* The corrected values exhibit improved agreement with the laboratory reference lux meter readings.
	* The results demonstrate the effectiveness of the calibration function in estimating the corresponding reference ~~illuminance~~ values.		* The results demonstrate the effectiveness of the calibration function in estimating the corresponding reference values.

	== Relative Error After Calibration ==		== Relative Error After Calibration ==
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	* The remaining error is considerably smaller than that observed before calibration.		* The remaining error is considerably smaller than that observed before calibration.
	* The calibrated LX-1108 measurements show improved relationship with the laboratory reference lux meter.		* The calibrated LX-1108 measurements show improved relationship with the laboratory reference lux meter.


			'''Important Limitation:'''

			* The function <math>TrueLux = Lux2Ref(MeasuredLux)</math> was derived exclusively from calibration data obtained using the LX-1108 lux meter and the laboratory reference lux meter.
			* The function is intended only for estimating reference-equivalent values from LX-1108 measurements.
			* The function was not derived using VEML7700 measurement data.
			* Consequently, the function cannot be assumed to provide accurate reference illuminance estimates for the VEML7700 sensor.
			* Since the VEML7700 exhibits different sensing characteristics and measurement behaviour, an independent calibration procedure is required to establish a corresponding calibration function.

	= Measurement Circuit =		= Measurement Circuit =

Onyesi-john.abiagam@stud.hshl.de: /* Measurement Method */

2026-05-30T19:10:03Z

Measurement Method

Onyesi-john.abiagam@stud.hshl.de: /* Measurement Method */

2026-05-30T19:05:45Z

Measurement Method

← Nächstältere Version		Version vom 30. Mai 2026, 19:05 Uhr
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	\| 4 \|\| SDA \|\| Serial Data Line for I²C communication		\| 4 \|\| SDA \|\| Serial Data Line for I²C communication
	\|}		\|}



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	* The resulting regression equation provides the mathematical basis for deriving a calibration function for the LX-1108.		* The resulting regression equation provides the mathematical basis for deriving a calibration function for the LX-1108.

	~~== Derivation of the TrueLux Function ==~~

	~~Using the nonlinear regression model derived in the previous section, the relationship between the~~ LX-1108 ~~measurements and the laboratory reference lux meter readings can be inverted to estimate the corresponding reference illuminance value from a measured LX-1108 reading.~~		== Calibration of LX-1108 Measurements ==

	~~Rearranging the~~ regression model:		The nonlinear regression model was used to establish a calibration function capable of estimating the corresponding reference illuminance value from a measured LX-1108 reading.

	~~<math>~~		The calibration function was subsequently applied to the LX-1108 measurements to obtain corrected illuminance values.
	~~\frac{~~LXReading~~}{a} = (LabRef)^b~~
	~~</math>~~		[[Datei:Corrected LXReading.png\|center\|thumb\|800px\|Figure 4: Corrected LX-1108 measurements compared with the laboratory reference lux meter readings.]]

	~~Taking both sides to~~ the ~~power of~~ <math>~~\frac{1}{b}~~</math>:		* The corrected measurements closely follow the ideal relationship (<math>y=x</math>).
			* The systematic deviation observed in the raw LX-1108 measurements has been substantially reduced.
			* The corrected values exhibit improved agreement with the laboratory reference lux meter readings.
			* The results demonstrate the effectiveness of the calibration function in estimating the corresponding reference illuminance values.

	~~<math>~~		== Relative Error After Calibration ==
	~~LabRef~~ =
	~~\left(\frac{LXReading}{a}\right)^{\frac{1}{b}}~~
	~~</math>~~

	~~Substituting the estimated regression parameters~~:		The relative error after calibration was calculated using:

	<math>		<math>
	~~LabRef~~ =		Relative\ Error =
	~~\left(~~\frac{~~LXReading~~}{~~1.428934~~}\~~right)^{\frac{1}{0.932233}}~~		\frac{LabRef-CorrectedLux}{LabRef}\times100
	</math>		</math>

	~~The resulting function is therefore~~:		where:

	<math>		* <math>LabRef</math> represents the laboratory reference lux meter reading.
	~~TrueLux = Lux2Ref(LXReading)~~		* <math>CorrectedLux</math> represents the calibrated LX-1108 measurement.
	</math>

	~~where~~:		[[Datei:Relative Error.png\|center\|thumb\|800px\|Figure 5: Relative Error After Calibration.]]

	* ~~<math>LXReading</math> represents the raw~~ LX-1108 ~~measurement.~~		* The relative error was significantly reduced after calibration.
	* <math>TrueLux</math> represents the ~~estimated~~ reference ~~illuminance value~~.		* The remaining error is considerably smaller than that observed before calibration.
			* The calibrated LX-1108 measurements show improved relationship with the laboratory reference lux meter.

	= Measurement Circuit =		= Measurement Circuit =

Onyesi-john.abiagam@stud.hshl.de: /* Nonlinear Regression */

2026-05-30T18:34:13Z

Nonlinear Regression

← Nächstältere Version		Version vom 30. Mai 2026, 18:34 Uhr
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	The model parameters were estimated using MATLAB's nonlinear regression fitting tools to obtain the best representation of the observed relationship between the laboratory reference lux meter and the LX-1108.		The model parameters were estimated using MATLAB's nonlinear regression fitting tools to obtain the best representation of the observed relationship between the laboratory reference lux meter and the LX-1108.
	~~=== Regression Results ===~~
	=== Regression Results ===		=== Regression Results ===

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	* The fitted model captures the systematic deviation of the LX-1108 relative to the laboratory reference lux meter.		* The fitted model captures the systematic deviation of the LX-1108 relative to the laboratory reference lux meter.
	* The resulting regression equation provides the mathematical basis for deriving a calibration function for the LX-1108.		* The resulting regression equation provides the mathematical basis for deriving a calibration function for the LX-1108.


	== Derivation of the TrueLux Function ==		== Derivation of the TrueLux Function ==

← Nächstältere Version		Version vom 30. Mai 2026, 19:10 Uhr
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	* The laboratory reference lux meter served as the reference instrument, while the LX-1108 was treated as the instrument under investigation.		* The laboratory reference lux meter served as the reference instrument, while the LX-1108 was treated as the instrument under investigation.
	* The relationship between the two instruments was examined over the selected illuminance range.		* The relationship between the two instruments was examined over the selected illuminance range.
	* Table X presents the recorded measurements obtained from both instruments.		* Table 1 presents the recorded measurements obtained from both instruments.
	* Figure X shows the corresponding LX-1108 measurements plotted against the reference lux meter readings.		* Figure 1 shows the corresponding LX-1108 measurements plotted against the reference lux meter readings.
	* The observed deviation between the two instruments suggests that the relationship cannot be adequately represented by a single constant correction factor.		* The observed deviation between the two instruments suggests that the relationship cannot be adequately represented by a single constant correction factor.

	'''Note:''' The analysis presented in this report is specific to the LX-1108 lux meter used during the experiment and should not be generalized to Ambient Light Sensors (ALS) or other light-sensing devices, as different devices exhibit different measurement characteristics and require independent calibration procedures.		'''Note:''' The analysis presented in this report is specific to the LX-1108 lux meter used during the experiment and should not be generalized to Ambient Light Sensors (ALS) or other light-sensing devices, as different devices exhibit different measurement characteristics and require independent calibration procedures.

	=== Table X: Reference Lux Meter and LX-1108 Measurement Data ===		=== Table 1: Reference Lux Meter and LX-1108 Measurement Data ===

	{\| class="wikitable"		{\| class="wikitable"
	\|+ Table X: Reference Lux Meter and LX-1108 Measurement Data		\|+ Table 1: Reference Lux Meter and LX-1108 Measurement Data
	! Reference Lux Meter (Lab_Ref) [Lux]		! Reference Lux Meter (Lab_Ref) [Lux]
	! LX-1108 Reading (LX_Reading) [Lux]		! LX-1108 Reading (LX_Reading) [Lux]
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	\|}		\|}

	'''Figure X''' illustrates the relationship between the laboratory reference lux meter readings and the corresponding LX-1108 measurements.		'''Figure 1''' illustrates the relationship between the laboratory reference lux meter readings and the corresponding LX-1108 measurements.

	[[Datei:Lab Ref Vs LX Reading.png\|center\|thumb\|800px\|Figure X: Reference Lux Meter Reading vs LX-1108 Measurement]]		[[Datei:Lab Ref Vs LX Reading.png\|center\|thumb\|800px\|Figure 1: Reference Lux Meter Reading vs LX-1108 Measurement]]

	* The LX-1108 readings generally increased with increasing reference illuminance.		* The LX-1108 readings generally increased with increasing reference illuminance.
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	where LabRef represents the laboratory reference lux meter reading and LXReading represents the corresponding LX-1108 measurement.		where LabRef represents the laboratory reference lux meter reading and LXReading represents the corresponding LX-1108 measurement.

	[[Datei:Error_before.png\|center\|thumb\|800px\|Figure X: Relative Error Before Calibration.]]		[[Datei:Error_before.png\|center\|thumb\|800px\|Figure 2: Relative Error Before Calibration.]]

	* The LX-1108 exhibited a systematic deviation relative to the laboratory reference lux meter.		* The LX-1108 exhibited a systematic deviation relative to the laboratory reference lux meter.