Temperature sensor on Trident: Is it reliable?


#1

Hi all,

I have recently received the Trident and I’ve already did some test dives. One of them was during a dive from the local SCUBA Divers’ Club. The Trident’s sensor was showing the temperature ~15.5-16 oC while the dive computers of the divers logged the water temp ~14 oC.

So, my question is what exactly does the temp sensor measures? Since I am also going to use the Trident for scientific reasons, I want to now if the measurements are reliable or just approximate values?

Thank you in advance!


#2

Greetings Allolas,

I’ll do my best to answer your questions. I believe the water temp comes from the pressure sensor as it uses water temp for depth calibration.

  1. The pressure sensor measures pressure and temperature. More specifically, the ms5837_30ba, which I believe is the correct sensor, datasheet is here, https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Data+SheetMS5837-30BAB1pdfEnglishENG_DS_MS5837-30BA_B1.pdfCAT-BLPS0017

  1. I think you’re asking about accuracy, which is given above, versus reliability. Is it reliable? I’ve never had a case where it stopped working or failed altogether, and I don’t believe anyone else has either. I could be wrong. It is reliable in the sense that it has always given me stable depth and temp data. And given the operating temp range, I’ve not seen it vary beyond ± 1 C.

As far as approximate values go, the RMS (Root mean Square) resolution error is listed above. You can compare that with the dive computers. I suspect the dive computers have a lower error bar on any single datum point. Being a diver, I would hate to think my dive computer wasn’t spot on since bottom time given depth is such a concern when you go deep.

However, it would be great if you had another temp sensor, calibrated, and log the temps to publish here. I think a few people would be very interested in the results.

In the end, the documentation gives this sensor a 2mm resolution for depth, but OpenROV states 1cm on the webpage, and ± 1.5 degree for temp. Looks like ~1.4 ft.lbs per square inch on pressure reads.

Thanks

Jim


#3

You are correct that the temperature information displayed is coming from the pressure sensor and is used for calibration of that sensor. The accuracy is in the range that @Jim_N mentioned (from the datasheet). It is meant more for general ideas on what the water temperature is, and not exact measurements for scientific reasons (assuming you need higher accuracy). What is the accuracy you would be looking for on the science side?


#4

First of all, thank you both for the replies!! I think I got my answer :nerd_face:

Now, regarding Brian’s question: One of the projects that I am planning on using the Trident is the monitoring of sea cucumbers’ populations in some areas of the Aegean Sea (Greece), by performing visual censuses with the ROV. So measuring the temperature at the sampling depth is a very useful information, from an ecological point of view. Given that the range of the measured values, as @Jim_N mentioned, is ~± 1°C, we should be covered, at least in the scope of the “general idea” you mentioned. :grinning:

In any case, we have a CTD (Seabird SBE 19) for higher accuracy, but it’s bulky (and of course, not as fun as the Trident!! :joy::joy: ), so I was thinking if we could take the precise measurements straight from the Trident.

Once again, thank you very much for your contributions!


#5

You are welcome!

Thank you for the explanation of the work you are doing. That sounds so cool and definitely makes sense of why temperature data would be helpful.

That is great that you have a CTD at your disposal, but I agree it is a little less fun.

Please keep us updated as you use both of these devices and anything you learn that is worth sharing with the community.