Vernier Light Sensor Lab

This lab introduces the student to the Vernier Light Sensor and teaches concepts in light

intensity. The student must learn how to connect to the ELVIS II prototyping board to

make the necessary signal connections for the sensor.

Theory:

Vernier offers a sensor that uses a silicon photodiode to measure light intensity. You will

acquire a voltage from the sensor and convert that to lux, the unit measuring illuminance.

How to build the experiment:

The light sensor is attached to the Analog Proto Board Connector (BTA-ELV), which is

connected to the NI-ELVIS II prototyping board.

Figure 1 and the following steps show how to wire the connector.

Figure 1: Prototyping Board for the Vernier Light Sensor

Wire the following pins:

1) AI 0+ to SIG 1 of the Analog Proto Board Connector

2) ELVIS DC Power Supply +5V to 5 V pin of the Analog Proto Board Connector

3) ELVIS DC Power Supply Ground to GND pin of the Analog Proto Board

Connector

4) AIGND to GND pin of the Analog Proto Board Connector

How the Light Sensor VI runs:

1) DAQmx VIs: An Analog Input Voltage task is created to read the signal from

channel ai0 on the NI ELVIS II. Since AI 0+ has been wired to SIG1 of the

Analog Proto Board Connector, we will be reading the voltages returned from the

Light Sensor. The task is configured for RSE, continuous samples, and the

sampling rate specified on the front panel.

2) Vernier Conversion VI: The conversion VI is specific to the Vernier analog

sensors. Based on the probe selected, it converts the raw voltage to a scaled value

of the appropriate units. The Light Sensor voltage is scaled differently depending

on the lux range selected: 0-600, 0-6000, or 0-150,000. The resulting value is in

lux.

3) Displaying the Data: The light intensity is displayed continuously on a chart as

well as a numeric indicator.

4) Stopping the Loop: The loop will run until one of the stop conditions is met.

Once the desired experiment length is reached, determined by comparing the

number of loop iterations to the target number of samples, the loop will terminate.

It can also be ended early by pressing the stop button.

Figure 2 below shows the LabVIEW code.

Figure 2: Light Sensor VI Block Diagram

Running the Light Sensor VI:

Before running the Light Sensor VI, verify that the physical channel selected is ai0 on

your ELVIS II device. Check that the range set on the sensor matches the range specified

in the Probe Selection control on the VI. Typically the 0-6000 lux range should be

appropriate. If you wish, choose a different experiment length or sampling rate.

Press the Run button and point the Light Sensor in the direction you wish to measure

light intensity. The lux measured should display on the Front Panel, as shown in Figure 3

below. Experiment with different levels of light.

Figure 3: Light Sensor VI Front Panel

If the values read are at the extremes of the selected range, adjust the range on the sensor

as well as the VI. If the data reaches the upper limit, select a larger range such as 0-

150,000 lux. If the data is 0 or close to 0, select a smaller, more sensitive range. This

may be necessary when measuring low levels of light intensity.

Summary:

With the Vernier sensors, you can take advantage of NI ELVIS II to acquire data by

plugging in with a simple Proto Board Connector. Collect analog data from the Light

Sensor using NI ELVIS II. Then use LabVIEW to display the various levels of light

intensity you measure.