Amphenol Air Quality Engineering Dev Kit - Review

Table of contents

RoadTest: Amphenol Air Quality Engineering Dev Kit - Industrial Sensing

Author: vannystick

Creation date: 31 Aug 2017

Evaluation Type: Independent Products

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: gp2y1010au Sharp dust sensor

What were the biggest problems encountered?: OLED screen failed following a few drops, assembly of sensors to shield is not very positive, humidity probe wire is very stiff

Detailed Review:

Summary

I have used this kit in a real world situation for several months and it has proven to be not only a useful tool but incredibly educational. The range of the sensors within the kit make it an excellent choice as a starting point for understanding air quality measurements. The kit offers extremely good value compared to buying the parts individually and is supported by clear, well documented and considered code for the Arduino. There is some room for improvement but my use of this kit is far from over!

This has been a great experience and I would like to thank neilsroberts for providing the kits

Let see how I got on. . .

Background and Application

I have been working in the automotive sector for ten years, and my company have been asked by a customer to investigate opportunities for improving air quality in the cabin. This is especially important in China where air quality monitoring is as common as checking for rain in the UK. My electronics (hobby) background gives me a good basis with Arduino, metrology and sensor kit design and packaging.

I am well experienced with cabin temperature and humidity and have a good understanding of what creates ‘comfort’ but my experience of air quality is a little limited. I expect to improve my understanding of typical cabin air quality and how it changes during a drive cycle. I will compare this against the air quality of the building I work in. I will explore the effect of some basic changes to improve cabin air quality with before and after evaluation of the changes. If time allows, I will compare the readings of the sensors against metrology systems commonly in use within the automotive.

You can read more about my back ground here Begin at the beginning. An Introduction.

Expectations

• This is an Amphenol product, I’ve been using their products for years, so I expect a well thought out solution which is both well supported and well documented. At the same time this is a road test, and while the product is on the market I won’t expect perfection.
• As per the Amphenol Advanced Sensors (AAS) website ‘The AAS-AQS-UNO engineering evaluation board is used to evaluate the Telaire range of air quality sensors’ so I will be looking at the sensors and shield while being less concerned about the Arduino Uno compatible its self.
• Because I want to road test the evaluation board in a real world situation I don’t expect a complete solution out of the box. I know I will want to add some logging functionality and changes to the code.
• There was a huge amount of prior reading and I started to feel like I had bitten off more than I could chew just reading through the specifications for the sensors. The main Telaire website is neat and simple and filled with tech specs, application notes, alternative sensors and more. It is also clear that these sensors are not gimmicks or cheap attempts at monitoring but something you can put directly into a product.
• Before starting to use a new sensor for the first time, I like to know my expected results. This will give me an indication if the sensor is reading right.
  • PPM2.5

The EPA Air Quality Index is a great place for acceptable limits of substances in the air.

• CO2
  
  Mikael Häggström of the Sundsvall Regional Hospital, Sweden produces some excellent medical images and infographics available on his Wiki page.

Unboxing and First Use

• The kit arrives in a simple, plain package which tells a lot about the intended purpose, it is not meant as a complete product but as a way of evaluating the AAS sensors. That said, coupling up with an Arduino compatible board, a custom shield and some very good code means it is pretty much a complete product.

• It also contains a short booklet with clear instructions on how to assemble the kit and get started. Initially this looked like a throw away, but it is very clear and very simple, I suspect it would be very handy if you where more Arduino coding based and less hardware based.
• Having downloaded all the source from the GitHub and already programmed another Arduino UNO to check the tool chain, I was keen to get it assembled, plugged in and coded up. On powering up it sprung straight to life having already been coded!

• In my view this is such a simple thing for AMP to do to bring some ‘surprise and delight’ to the kit. Normally kits like this need setting up, sometimes a bit of fault finding is the hardware has changed a little. Not in this case!
• You can read more about my initial thoughts on the kit here RoadTest - Amphenol Air Quality Kit - Quick First Impressions

Hardware Observations

• In my case the kit has travelled over 3500 miles to the UK. The assembly of the Arduino compatible, shield and OLED screen has not travelled unscathed
  • The bag the assembly has shipped in is undersized making it rather difficult to get out
  • The connector on the shield is bent
  • The pins on the OLED plug in are bent

• Perhaps more of an irritation, palm to head, is the orientation of the PCB screen print on the Arduino compatible compared to the shield. The shield is upside down! This has perhaps been forced by the placement of the dust sensor, it is easier to read the print up to the sensor rather than over, but it just feels wrong.

• PCB screen on shield CF OLED
  Wording on the OLED and AAS shield are not consistent (VCC Vs 5V), I suspect this is variation in the sourcing of the OLED as can often be the case.

• PCB screen on the CO2 sensor
  There is no writing on the PCB screen around the CO2 sensor, and it is very easy to get the sensor plugged in the wrong way around. There is a single square through hole on the sensor and I assume this relates to GND, but I would like to see it labelled.

• Connectors on all of the sensors are not reliably poke-yoke. Without excessive force all of the sensors could be plugged into the shield the wrong way around. To an extent this is taken care of by the images on the pamphlet that comes with the kit, but the quality of the connectors combined with the lack of sensor to shield screen print is concerning.

• CO2 sensor mounting
  The CO2 sensor is a little precariously placed on the top of the board being only constrained at one end. I would like to see some support at the other end of the carrier board with a standoff or movement of the pins on the PCB. Given the application of the kit, this is probably not critical.

• What else am I missing?
  The shield has multiple extra connections, one labelled for blue tooth. There is source code for a number of extra sensors/accessories, but it not clear in the documentation that is shipped with the kit what is missing and why. The Telaire site does list a number of optional accessories for the kit, its just a shame they are not included or better documented in the accompanying booklet.

Recommendations

• The Arduino compatible and shield should be shipped in a larger bag and separate to the OLED screen to avoid damage and make it easier to remove from the bag.

Arduino Code

• The code supplied for the kit (available from the AAS GitHub) is excellent. It is not the smallest code, nor the fastest operating but it has an excellent structure and is really well commented. I’ve actually learnt a few new programming techniques from it.
• Initially the code would not compile, using Arduino 1.6.7, Adafruit SSD1306 was not present in libraries and had to be sourced. I hadn’t noticed it in the libraries folder on the Telaire git hub. Lesson to self, look twice!
• Because I want to use the kit in real world situations, while I’m driving, I have added a DeekRobot Data Logging shield from Hobby Components. This features a real time clock and SD card enabling logging as soon as the Arduino compatible is powered!

The Sensors

Temperature and Humidity

The T9602 temperature and humidity sensor is an excellent package size for use in the cabin. Typically I would use a much large probe which is intended to be used outside the vehicle and becomes quite clumsy inside the cabin, so the T902 is a really good solution for me in every day testing. Operating range and accuracy for humidity is right where I need it to be for my application, although a temperature operating range of -20c and +70c would probably cause me issues. I regularly see cabin temperatures exceeding these limits (real world) which suggests the sensor is geared at indoor measurements only (despite being IP67 rated).

One issue I did find, repeatedly, with this sensor was the cable. It was far too stiff for the way I wanted to use it and I wanted to measure temperature and humidity in the same air stream as the dust sensor, this became quite a problem. Ultimately I resorted to a spot of carpentry to wrestle the cable under control.

$52.42 Digi-key

Dust Sensor

The SM-PWM-01C dust sensor is a far superior looking sensor to many of the cheaper rivals, perhaps simply because of the black PCB or neatly arranged components with clear and contracting silk screen. It has very good performance to match. While more than double the price I have paid for an older designed Sharp sensor, GP2Y1014AU0F, the SM-PWM-01C reading was more stable and consistent perhaps simply because it is digital.

Like the temperature and humidity sensor, the dust sensor is also specified to be used indoors in a more controlled environment than I would normally test in. An operating temperature between -10 and +60c just won’t cut it in an automotive application. I have now tested at -20c in a controlled environment without issue, although I have no reference sensor to test against. It is also not clear how the sensor would react to sudden temperature changes. I suspect the readings might be out if condensation forms on the reflector mirror or IR sensor.

Without an aspirator fan, the dust sensor must be located in a vertical position and directly in the flow of air to be measured. For an automotive application this simply won’t be possible to package, so it is likely that that an aspirated version from a competitor will be required.

Despite the limitations for application, the learning derived from this sensor has been significant and invaluable as we will see below. I suspect a laser version of the sensor would potentially overcome many of the limitations.

$14.82 Digi-key

CO2 SENSOR

The T6713 carbon dioxide sensor is truly remarkable and the part of the kit that I have most enjoyed working with. To think that so much information can be gleamed from such a small package is astounding. Again operating and storage temperatures would cause concern for automotive application, but the potential for this sensor in the cabin makes me think this limitation could easily be overcome. I’ll come back to this sensor later.

$93.86 Digi-key

OLED Screen

Okay, the 128 * 64 OLED is not a sensor, but it is a significant part of the package. I’m used to using Arduino with screens and have plenty lying around, but to include it really does make the kit a full and complete package. I like the colour combination and it is very clear in all ambient lighting conditions.

Unfortunately in my case, a few unexpected trips around the foot well of the car didn’t do the screen any good and it failed. It actually took some time before I found this out as I had only been running with the logger and not the display output.

~$20 from many sources

Value for Money

I've put the DigiKey current prices in to show how good the value of the kit is compared to buying individual sensors is.
Total price for sensors alone is $181, the Digi-Key price for the whole kit is just $143.55, and the includes the shield and Arduino compatible with great source code to go with it!

Baseline Testing

For an initial test, I set the kit up on my desk and let it record for a day. I expected to see nice stable conditions as the desk is far from any doors (or windows) and well-conditioned. I wasn’t disappointed, the logger worked well, the traces are relatively flat and the spike in CO2 around 3000s can be attributed to a desk based meeting of minds (or lunch).

The two spikes are caused by movement rather than a bad sensor.
The values meet previously defined expectations giving good initial confidence in the readings.

Vehicle Testing

At the time of writing I have logged over 50 hours of data in car with the sensor mounted between the head rests of the car (yes that is a stick and cable tie assembly).

I don't intend to bore the reader with a graph of every single trip, but I thought it would be interesting to see some of the real world testing

The graph below shows a typical drive cycle, short town traffic followed by highway (60 to 70 mph) for 40 minutes. At initial look it would appear that dust level is proportional to speed, but further data analysis has shown that the other vehicles on the road at the time have a bigger influence. For example if I follow a couple of lorries then the dust level is far higher than if I am on an empty highway. I put this down more to up-draft of dust from the road surface than vehicle emissions.
It can also be seen that the climate control system is doing a good job of managing the temperature and humidity of the cabin.

For similar driving conditions, with AC off (compressor disengaged) we see a notable increase in humidity as the air is not being dried.

Again for similar driving conditions, with the climate system locked in re-circulation mode, we see a steadily growing CO2 level which reaches levels consistent with poor concentration, loss of attention etc. This is not a surprise as the cabin air is not being replenished, but does offer an opportunity to improve cabin air quality by limiting the duration the system can stay in recirculated air mode for example.

It is clear in all of these traces that the CO2 level starts quite high and drops down. The technical note for the sensor does specifically note that the sensor takes 5 minutes to warm up and give a stable reading.

Sensor Accuracy

I don't have access to a calibrated CO2 or dust monitor, comparing the AAS dust sensor to the Sharp sensor while comparable levels the AAS sensor gave a more robust value (not cutting out) with far less noise on the reading making it more reliable for making decisions from.
I was able to use a calibrated Testo meter for temperature and humidity, the results where very pleasing, the AAS sensor having slightly more noise but both well within measurement error.
I would like to compare against calibrated or reference air sample in the future.

What is Next?

Well I have by no means completed the testing I want to do on this kit, it will continue to run in the vehicle for a good while yet. It is also likely that my company will look to buy another set of kit to use in our overseas development centre. Personally I would like to get a case designed and made and have this series of sensors as a standard part of our instrumentation list.