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Skipped Scans using SDI-12 with CR6 at 1-Second Scan Interval

dbrese_stone-env Mar 28, 2019 08:03 PM

I have a CR6 running at a 1-second scan interval with 4 CS215 SDI-12 temperature/RH sensors and 4 two-dimensional sonic anemometers. Any scan interval below 10 seconds creates skipped scans in my output table. After consulting with tech support, I have tried the M! and C! commands to change the way the SDI-12 sensors are scanned compared to the other sensors with no change. I have isolated the problem to the SDI-12 sensors by removing the other sensors from the program and vice versa. Only the program with the SDI-12 sensors creates skipped scans. The odd part is that the measurment and processing time are well below the 1-second interval.

I would normally increase the scan interval to 10 seconds and call this issue fixed. However, in order to meet the requirements of my analyses, I need the 1-second resolution in the data from the anemometers. 

Can anyone shed some light on how to increase the scan interval without creating these skipped scans?   

DAM Mar 29, 2019 04:51 PM

Could you read the SDI-12 sensors from a slow sequence at a slower rate? 

dbrese_stone-env Apr 9, 2019 03:24 PM

That is exactly what I needed! Thanks for the suggestion. I looked into this and all I needed was a second scan codeblock in the main program. I edited my code to include the SlowSequence and now I am in business again.

smile Apr 10, 2019 10:31 PM


The anemometers what output have?
You could decrease the response time of the SDI-12 sensors (notoriously slow, even a few seconds each) with the R command instead of M. With a multiparameter Vaisala probe I solved this, greatly reducing the times but consuming a little more energy .
Also you could read one at a time, every 4 scans, ex. on the second 1 you read the sensor 1 on the second 2 read the sensor 2 on the second 3 the sensor 3 and on the second 4 the sensor 4 and then start again, on the second 5 the sensor 1 and so on. I fear, however, that even with just one sdi12 and the anemometers, you won't stay in the second. Maybe you should use analog sensors.



dbrese_stone-env Apr 11, 2019 12:51 PM

Hi Smile,

I have resolved the issue with a secondary scan with a 10-second interval after the main scan with a 1-second interval. I only needed the anemometers to log at 1-second while the temp/RH sensors need 10 seconds. However, I think your approach is smart. The only thing I cannot understand is how the processing time for each scan in my previous program was taking far less than a second, but the logger was still skipping scans. 

priyankaa Mar 21, 2024 07:02 AM

This post is under review.

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