I received my D on 6 July and I’ve made some notes of observations and questions from over the past two weeks. Overall, it works quite well.

Hardware
1. The PCB in mine seems a little loose and rattles if softly shaken lengthways. I suspect it might need a thin piece of medium- or high-density foam on the inside of the top and/or bottom plates
2. The power switch moves the entire PCB lengthways, before operating (see previous point)
3. How should we orient the device if sitting at desk (for example) – it seems as though there are sensor or antenna holes on all surfaces, except the curved sides, and the USB cable also complicates things
4. The lag on the touchscreen can be a few seconds, at times – I’ve noticed as much as 8-second jumps, when on the Measures screen
5. What is the black antenna/sensor on the front, above the screen? It’s not described in the specifications on the website.

Battery

6. It won’t power up if connected to charger but it will charge after being powered up; so, if the battery is empty, you need to press the On button and then immediately connect power, otherwise it will power-down again
7. It seems to power down if connected to a PC but then appears as USB-serial port; this is fine if you have AC USB adapters everywhere but means that you can’t use a PC/laptop to charge it and have it uploading at the same time
8. Are you planning to release firmware updates for the Model D? Is that what the USB-serial functionality is for?
9. The battery indicator didn’t reach full, from empty, after being connected to a 5V/1A USB charger for 8.5 hours uninterrupted, despite only drawing 0.5A; it does with a 5V/2A charger. This may have been location specific – at my office it can’t receive a GPS signal and the wireless is busy, so that may use more power
10. Battery life seems to be about two-four hours

Software

11. General
    1. There is no explanation for the colours of the icons on the top bar; I think I’ve established that grey means off, green means on and blue means connected
    2. Waking up the screen shouldn’t also perform whatever action is under the area touched to wake-up; since the screen isn’t readable when off, the first touch should just wake it
12. Wireless
    1. Wireless config – if you were viewing/setting the Wi-Fi key and exit back to the Settings menu, when entering Wi-Fi settings again, the SSID button is selected but it displays the key
    2. Wireless config – the keyboard shows each key as being depressed for each character used in the SSID or key
    3. It only seems to connect to the configured SSID if its broadcast – is that correct?
    4. A single SSID is a moderate limitation, particularly given the method of configuration. A method of saving a couple of profiles would be handy, even if the profile has to be manually selected
13. Offline
    1. Could you add an option to automatically upload offline data when reconnected?
    2. The offline samples counter resets after power-cycle – I initially, wrongly, assumed that it was losing offline data after reboot (battery was drained)
    3. Whilst uploading offline data, it doesn’t seem to be also uploading live data or adding it to the offline file, to be uploaded after the sync
    4. Whilst uploading, the battery indicator is hidden but the screen stays on – so it drains the battery quickly but you have no idea how much battery is left
    5. If the battery runs out whilst uploading offline data, it starts again when another sync is initiated after powering back up
    6. Estimated time for upload of 912 updates is 912 seconds however, for me, each update took ~5 seconds to upload, so it took ~95 minutes. This number could adapt over time, with a value saved to NVRAM or SD (wherever you save Wi-Fi settings), or at least adapt during the current sync session. Using my phone as a hotspot, it was taking ~7-8 seconds per sample.
14. Measures
    1. Barometric units – can this be changed to hPa or mbar (which are equivalent)? 101000 Pa seems silly for pressure, when weather services use 1010.0 for the same pressure
    2. Switching the labels and values between sides on the Air Q screen would enable you to change the units from Pa to hPa without losing precision, although I doubt anyone would mind losing hundredths of hPa
    3. “Alarm” on the notification bar doesn’t tell you which parameter is triggering the alarm

Last Wednesday (12/07/2017) I flew from Adelaide (AU) to Sydney (AU), and back again on Friday (14/07/2017), which is approximately 1600km in each direction; the plane was a 737-800 for both flights.
On the flight to Sydney, I had a middle seat (14B) and the GPS lost signal at ~8500m altitude (my Seiko Astron GPS watch was also unable to receive a signal at this altitude) and recovered as we descended down through ~8500m. I thought this might have just been a thing with consumer GPS but on the return flight, however, I had the terrible windowless window-seat 9A and I was able to orient it so that I could receive a GPS signal for most of the flight.
You can see the flights, using the dates above, here; the flights themselves become quite obvious, when you change the sensor to radiation, due relatively large spike in dose rate.
Later on Wednesday evening I was finally in a position to reconfigure the D to use my mobile hotspot; there should have been about 2500 offline samples from ~7 hours with no wireless but when I entered the sync menu it reported only 1494. Upon tapping SYNC, the counter started increasing at a rate of about 5 <i>per second</i>, with no sample information in green below the counter, so I figured that it probably wasn’t doing anything, and it blew past the 1494 in no time. Of course, there is no way to stop an offline sync and the power switch only functions to turn it on (holding it for 10+ seconds didn’t do anything) – I wondered if I was going to have to let the battery drain, as the counter went on to well past 20,000/1494! Fortunately I remembered that plugging it into a computer and allowing it to install the USB-serial driver causes it to reboot into some sort of maintenance mode, which it did as I expected. After then disconnecting and powering up, and going to sync, it was at 1498 samples, which would include the four after booting.
I think something happened with regards to the SD card, whilst on the flight, since late in the flight I noticed the measures screen reported that the SD card was 0MB – I couldn’t remember if it always said that whilst offline or not, so I didn’t do anything about it; obviously this was a mistake, since it meant that I needlessly carried it around for ~3 hours whilst it wasn’t able to actually save samples.
Perhaps an alarm could be displayed if it loses the SD card, whilst powered on – particularly if it’s not connected to Wi-Fi.
The SD card also went offline after landing back in Adelaide, some time during my drive home, and it’s done it a couple of times since then. I’ve never touched the SD card, let alone remove it, so I’m not sure what the issue is.

As I said at the beginning of this rather lengthy post, overall it’s quite good.

Please let me know if you would like more information – or less 🙂