Severn Evaluation Kit

Kit overview

LAIIER’s evaluation kits have been designed to help you evaluate our technology for whichever use case is required. This user guide will instruct you through setting up the relevant sensor hardware and software to allow for effective data collection and/or visualization.

This kit is the Severn Evaluation Kit that is suitable for detecting any liquid that comes in contact with the sensor. Each kit comes with one Severn Evaluation Board and three Severn Sensors.

After following this user guide, you will be able to scope the performance of these sensors and test their suitability for your application.

Theory of operation

Severn Sensors:

Our Severn Sensors are based on resistive sensing. Conductive ink is printed into a unique pattern that divides the print into twelve sensing segments allowing the liquid to be detected by a specific part of the sensor. Within each segment, there are several pairs of conductive tracks and when a liquid bridges these tracks, there is a change in electrical resistance. This signal can be detected and filtered by the microcontroller on the Severn Evaluation Board.

The distance between these individual tracks determines the sensor’s sensitivity so narrower gaps can detect smaller droplets and vice versa. As this sensor detects the change in resistance, it has been tested to be optimal for conductive liquids (i.e. ionic and/or polar materials).

Severn Evaluation Board:

Within the kit, you will find the Severn Evaluation Board. This board has been manufactured specifically for the Severn Sensors and its future updates. It includes a microcontroller chip, FFC connector, power switch, and a Micro USB output port. You may notice an Arduino footprint has been used on the board which will allow for further capabilities in the future. The Micro USB port outputs serial data of the sensor's measurements which is explained in the instructions.

Instructions

Software setup

1. We recommend the software CoolTerm, which you can download here and download the version according to the operating system you are using
2. Once the Evaluation Board is plugged into a PC USB port and powered on, open CoolTerm
3. Within CoolTerm, open Options
4. Select the port where the LAIIER board is plugged in, the name should be similar to “usbmodem14301”
5. Set the Baudrate to “115200”, Data Bits to “8”, Parity to “None” and Stop Bits to “1”
6. If you need timestamps, open the Receive Options on the left hand pane and under Capture File Options, tick “Add timestamps to captured data”
7. Click OK to save and then click Connect to start
8. CoolTerm will now display the sensor’s readings
9. To capture data in a txt file, go to the Connection menu, then Capture to Text/Binary file and then click Start
10. Save the file to your directory
11. When finished capturing data, navigate back to Connection, Capture to text/binary file, then Stop

Excel setup

1. In order to plot the data with Excel, first open Excel and then within Excel, open the CoolTerm text file
2. Select “Delimited” and in the next screen check “Tab” and “Space”
3. Set the date format to “YMD” and then click “Finish”
4. Delete the first row that contains “TOUCH:” or “DIFF:” in the column “C”
5. Select column “C”, which contains “TOUCH”, “FDAT” and “DIFF”, and select Filter
6. Unselect all options but “FDAT”
7. Insert a column next after column “C” to specify the time in seconds
8. Readings are roughly every 4 seconds so create a sequence as shown
9. Select all 13 columns D to P for plotting
10. Plot a scatter graph
11. Format the scatter graph to what you require

Experiment setup

Once you have everything set up, you are ready to conduct your experiments. Our Severn Sensors are able to detect a range of liquids, so you can drop various liquids onto the sensors. You should see a change in numbers within CoolTerm. It is also important to note when exactly you have introduced a change for the sensor to detect so it will be easier to analyse results afterwards, e.g. dropping liquid on the sensor 10 seconds after the sensor is recording data.

Best Practices

Cutting sensor

The Liquid Leak Sensor has multiple sensing segments due to the unique print pattern. This means that the sensor can be trimmed at certain places to suit the desired length and size. In order to do so, please follow these steps:

1. Power off and remove the sensor from the board
2. Using scissors or a cutting knife, cut the sensor to the size for your use case
3. Reconnect the sensor back to the board and power the board

Note that even though the sensor has been cut, you may still get a reading for those points that were removed; these readings can be disregarded. 

Sensor installation

In order to make sure sensors are installed correctly and allow for efficient experimentation, follow these steps:

1. Make sure any surface is dust and debris-free before sticking the sensor down to improve adhesion
2. If testing is on a delicate surface, test a small part of the adhesion first to prevent potential damage
3. When setting up, position the sensor and the board enclosure first before peeling back the sensor’s adhesive side; this can help you plan the best setup without having to restick the sensor

Initialization checks

Between experiments, make sure all sensor segments are wiped clean with water (distilled is the best) and dried. This will ensure all initial readings of the sensor are at the normal level.

Make sure all values are what you expect them to be with some quick sanity checks. For example:

• Values should start off stable and at the initial values (ie. 1023 for all 12 sensing segments)
• Values should be between the minimum and maximum points
• When a conductive liquid is sensed, it should have a noticeable change in signal

Contact

If there are any issues or questions that have not been answered in this guide, contact info@laiier.com and we will get back to you shortly