The purpose of this article is to provide a simple demonstration to show the capabilities of the pressure sensor in our evaluation kit.
SetupI first had the three sensors powered up and reporting every 30s to the cloud. I leveraged a dashboard panel from a previous project posted here and modified it to look for the three specific sensors I was targeting. My focus of the dashboard was to visualize the impacts of the vacuum pump at different stages on 2 sensors within the bag while 1 remained outside.
I then set up the sensors. 2 sensors were first placed within the mesh that comes with the kit while the third sensor remained next to the bag. The purpose of the mesh is to allow air to continue to have a path to evacuate the bag as efficiently as possible. Otherwise, there could be air pockets that get trapped and could eventually move within the bag and change your pressure results.
I placed the sensors within the bag with one directly below the valve and the other next to it.
The bag was then sealed shut with the adhesive strip that is included in the kit.
ActivityI started to pump the air out of the system in stages. I wanted to track the results from each sensor to see if they remained consistent between the two. Each time I pumped it down to create a vacuum, I did it in multiple stages. The hand pump was extremely easy to use and very effective. It quickly becomes challenging to pull more air out of the bag and you can monitor those results in Grafana.
The above chart shows the effects of 3 different steps I took while pumping down the bag. You will notice that the sensors tracked each other perfectly. The slight variations in the chart are from variations of when the sensor took the measurement. Because the sensors will report when bumped, the sensors often report slightly out of sync with each other during the pump down steps. As they stabilized, I always saw them settle into identical results.
I ran the test as far down as I could go which bottomed out the sensor at its minimum limit of 300 mbar. I let it sit there for a while before letting the air back into the bag in short bursts.
I ran through this test sequence twice from no vacuum down to < 300 mbar and then back to 1bar.
In addition to noticing the pressure results, you can also see the difference between a sensor with its PV cell covered vs one that’s not. The uncovered cell, while still in the bag, maintained its SCAP voltage while the sensor underneath the valve started to draw down its SCAP voltage to continue to properly function.
It's important to note when working with batteryless devices, the harvesting sources are critical, so understanding these subtleties is vital when deploying sensors.
This test was a quick way to show the effectiveness, responsiveness, and consistency of the pressure sensor results between 2 devices. It helped to also demonstrate the effects of different harvesting conditions of two parts right next to one another.
Comments
Please log in or sign up to comment.