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Hydromoth recording error mid-deployment

I have two hydromoths and both are experiencing similar problems when deployed. The initial recordings are fine for around 5 days (producing files of the expected length) and then the recording schedule seems to be disrupted, producing errorneous files not following the configured recording schedule.

The file outputs and my config files are pasted below. I was using duracell plus AA batteries and samsung evo 256GB micro SD cards.

For future deployments, I'd like continuous recordings (ideally 1 h files, 24 hours a day) at 96kHz. This was initially happening in the second deployment, but then something seems to have gone wrong in the 20230911_160120 file onwards. The start file time is correct, but each file is only a couple of minutes long.

What could be causing this issue? Is this an error with the devices or the config files?

Thanks in advance!

Laura

Deployment 1 (switched to default not custom so did not get 1h files):

Device ID : 242A260463FB81B1

Firmware : AudioMoth-Firmware-Basic (1.8.1)

Time zone : UTC

Sample rate (Hz) : 96000

Gain : Low-Medium

Sleep duration (s) : 5

Recording duration (s) : 3600

Active recording periods : 1

Recording period 1 : 00:00 - 24:00 (UTC)

Earliest recording time : ---------- --:--:--

Latest recording time : ---------- --:--:--

Filter : -

Trigger type : -

Threshold setting : -

Minimum trigger duration (s) : -

Enable LED : Yes

Enable low-voltage cut-off : Yes

Enable battery level indication : Yes

Always require acoustic chime : No

Use daily folder for WAV files : No

Disable 48Hz DC blocking filter : No

Enable energy saver mode : No

Enable low gain range : No

Enable magnetic switch : No

Enable GPS time setting : No

Deployment 2:

Device ID : 245AAA0563FB735B

Firmware : AudioMoth-Firmware-Basic (1.8.1)

Time zone : UTC

Sample rate (Hz) : 96000

Gain : Low-Medium

Sleep duration (s) : 5

Recording duration (s) : 3600

Active recording periods : 1

Recording period 1 : 00:00 - 24:00 (UTC)

Earliest recording time : ---------- --:--:--

Latest recording time : ---------- --:--:--

Filter : -

Trigger type : -

Threshold setting : -

Minimum trigger duration (s) : -

Enable LED : Yes

Enable low-voltage cut-off : Yes

Enable battery level indication : Yes

Always require acoustic chime : No

Use daily folder for WAV files : No

Disable 48Hz DC blocking filter : No

Enable energy saver mode : No

Enable low gain range : No

Enable magnetic switch : No

Enable GPS time setting : No

5 comments

5 Comments

Laura Palmer

Sep 20, 2023

Thank you very much for this - it is really helpful.

I think we will proceed with a duty cycle.

All the best,

Laura

Alex Rogers

Sep 13, 2023

Hi Laura,

Normally, files that are smaller than requested are due to the battery voltage being low during the recording. If you open a short file in the AudioMoth Filter Playground (https://playground.openacousticdevices.info) and click on 'Show file information' it will show you the WAV header comment information. This will probably report that the recording stopped early due to a low battery voltage. The expected energy consumption is given in the Config App:

The five day recording period that you observed is quite short. However, the value in the Config App is calculated for 32GB SanDisk Extreme cards. Different cards have different energy consumption so it may be that the Samsung EVO 256GB uses significantly more energy. If you can confirm the exact model, I can double check the actual energy consumption of the card.

For the next deployment, if you use a recording period of 3595 seconds and a sleep duration of 5 seconds, then you will get recordings that start on each hour.

For continuous recordings at high sample rates, Energizer Ultimate Lithium batteries will give you the best energy capacity - https://www.openacousticdevices.info/batteries - as they maintain voltage for much longer and have a greater overall capacity. Alex

Laura Palmer

Sep 14, 2023

Replying to

Hi Alex,

Thank you for your prompt and very helpful reply. It does appear that this was due to the battery voltage.

The SD card model I've been using is: MicroSD Samsung 256GB SDXC EVO PLUS MB-MC256HA/EU. We are hoping to maximise the deployment duration so in future I will use the Energizer Ultimate Lithium batteries. Do you know of any rechargeable options that offer the same capacity? We are typically getting around 76GB of data so ideally I need an SD card with 128GB capacity and minimal power consumption. Would you recommend the Sandisk Extreme models?

Thanks again,

Laura

Alex Rogers

Sep 17, 2023

Replying to

Hi Laura, I measured a number of SD cards, including the Samsung EVO Plus 256GB card that you used, with your settings. The Samsung card is actually pretty good. It is higher than the SanDisk Extreme 32GB card that the Config App reports but only a little higher.

380mAh - SanDisk Extreme 32GB

490mAh - SanDisk Extreme 64GB

620mAh - SanDisk Extreme 128GB

525mAh - Samsung EVO Plus 256GB

The highest-capacity rechargeable batteries are 2850 mAh so you are still at about five days duration if you want to record continuously. You can reduce the energy consumption by duty-cycling (i.e. recording one hour in two) or recording at a slower sample rate. At 48kHz, the 'energy saver mode' is also an option which reduces consumption a little more. I've ordered a Samsung EVO Plus 128GB card to try out. This should have slightly lower energy consumption. I'll also check if we could extend 'energy saver mode' to 96 kHz sampling which would potentially reduce energy consumption a little more as well. Alex

Alex Rogers

Sep 19, 2023

Replying to

I also measured the 128GB card and found it has the same energy consumption as the larger 256GB card. 525mAh - Samsung EVO Plus 128GB It would be possible to make a custom version of the firmware that supports energy-saver mode. This sacrifices some recording quality by oversampling less, but will extend the deployment by about 15%.