What's going on here? - Page 1
Forum section: electronics / projects

author: v8dave
author_rank: Regular Contributor
timestamp: December 23, 2015, 02:01:40 am
content: Here is an interesting one for you to look at.I have deployed a data logger in Texas oil field in a remote location and using GPRS via AT&T we are sending the data for a number of sensors to a SCADA server running Mango Automation. This is for a friend who has a small lease hold and we wanted to monitor some pressures and temperatures at the site whilst he wasn't there.The attached chart shows the temperature for the last 11 days up until now (Wed 23rd Dec 15) and we have a strange occurrence with the system that we can't yet explain. We stop getting data every night anywhere between 10pm and midnight. It is not always the same time. It comes back on in the morning. Each data message is timestamped from the logger so we know that what we see is the data from the field. When there is no data to the SCADA server, it simply logs the last reading every min which is why we see the straight line on the graph. The time stamp data is a string so the SCADA does not log this if there is no data so we can see the time stop updating from the logger by reading these records.What's interesting is that the stop and start time temperatures are the same or very close within 1 or 2 degress when I look at the raw data. We don't think we are losing power at the site although this is still to be confirmed but it would not explain why the temperature is the same each time it restarts. The logger is rated for -20 to 85C and I will shortly be testing one in a fridgeto see if there is anything strange around the 50F (10C) temperature range. I've had units installed and working down to -5 so I don't see any issue here with it but will test this.If it was power loss or even GPRS loss for the time I would expect the temperature to be different but in this case we see the same when it comes back on. The other sensors (pressure) show the same thing but as they don't swing as high, they are not so easy to show on a graph.My friend will be back in Texas in the new year and will check it more but it sure is a strange one.

author: jeroen79
author_rank: Frequent Contributor
timestamp: December 23, 2015, 02:55:37 am
content: Maybe something is sensitive to temperature/moisture/condensation?This could also be the GPRS unit, power supply or cabling.Does the logger save any data locally or does it just send it out and forgets it?If it does then you could check if anything was logged -and thus the logger was working- during the blackouts.How about sending someone over there for one night to watch the setup?Do the various components have any external indicators (LEDs) to show if they are working?I'd rig up something to monitor voltage and current for the various components.

author: v8dave
author_rank: Regular Contributor
timestamp: December 23, 2015, 03:02:29 am
content: It would certainly seem to be temperature related. The fridge test should show this. Seems strange though that it comes back on at the same temp it went off. That's the weird partThere is no locally saved data at present but a new update will fix that so we will be able to compare but won't be able to install this until late January. As this was to be a remote monitor, local recording was no considered as there would not be anyone to download the data until the tanks were ready to be emptied which is why we monitor them.There is no one who can be on site as the location is basically out in the middle of nowhere and a few hours drive from town.The logger has an LCD display so this will show what is happening if we had someone out there.I plan to get the other logger I have here hooked up to temperature test later today.

author: wblock
author_rank: Regular Contributor
timestamp: December 23, 2015, 04:31:00 am
content: Quote from: v8dave on December 23, 2015, 03:02:29 amOr a video camera, which along with a timestamp could capture the display of a DMM or even an oscilloscope connected to the important parts.

author: w3amd
author_rank: Regular Contributor
timestamp: December 24, 2015, 01:40:52 am
content: It would be helpful to show the data points collected in the graphs with marking points. Does the data really show no signal between 10PM and 2AMish? I dunno. The flat parts seem to show when the signal disappears. Some of those lines between 10PM and 2AM don't look linear so they suggest data points between.Also is this above ground or below ground sensing? The temperatures at some times seem to move way to much and look quite noisy.JohnW3AMD

author: v8dave
author_rank: Regular Contributor
timestamp: December 24, 2015, 05:53:09 am
content: Hi John,The timestamp from the logger is a string and this shows a gap in the reception.The straight line is simply the SCADA system using the last known value to record to the database every minute.The raw data shows that the data value starts around the same value for temperature. For pressure (see attached) we get the next reading and you can see the step in the attached graph indicating that the pressure was continuing to increase during the data loss period. It's noisy due to the pulsing from the 8 or so beam pumps all feeding the one line into the tank.The temp sensor is located above ground on an inlet pipe to the oil storage tank.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2015, 06:33:04 am
content: Is there a cleaning lady?

author: v8dave
author_rank: Regular Contributor
timestamp: December 24, 2015, 06:34:27 am
content: Quote from: Fungus on December 24, 2015, 06:33:04 amIt's in the middle of nowhere so I doubt anyone will be out there. About once a week someone checks the site.

author: w3amd
author_rank: Regular Contributor
timestamp: December 24, 2015, 07:06:17 am
content: Is the sensor a thermocouple? Is there a partial connection on the sensor wiring? Any correlation between pumps on and temperature disappearing?

author: ataradov
author_rank: Super Contributor
timestamp: December 24, 2015, 07:15:05 am
content: Is there an explanation for this pressure behavior? In all active periods it seems to be falling, then raising again, and then device cuts off.

author: v8dave
author_rank: Regular Contributor
timestamp: December 24, 2015, 07:20:08 am
content: It is a thermocouple with a 4-20mA driver.All of the sensors stop being recorded on the SCADA system. What we don't know at this time is if the power is going off on site but they are sure that it is constant.Until we upgrade the software to record data locally we won't know this. This is planned for late January.

author: v8dave
author_rank: Regular Contributor
timestamp: December 24, 2015, 07:24:11 am
content: Quote from: ataradov on December 24, 2015, 07:15:05 amHi Alex,Yes, we know there seems to be a temperature effect on the sensor but the client is only interested to see that the pressure is increasing over time and it is. We could compensate for this but he seems happy with the results so far. Our main concern is the loss of data which we have not been able to determine the reason for. For the time being, as long as it recovers every day we have valid data we can use.

author: Fungus
author_rank: Super Contributor
timestamp: December 24, 2015, 08:07:07 am
content: Quote from: v8dave on December 24, 2015, 06:34:27 amDon't rule out critters...

author: v8dave
author_rank: Regular Contributor
timestamp: December 24, 2015, 08:08:36 am
content: Quote from: Fungus on December 24, 2015, 08:07:07 amWhat, with excellent timing?

author: dexters_lab
author_rank: Unknown
timestamp: December 24, 2015, 10:56:15 am
content: given there is variance in the temperature this happens i would suggest it might be related to humidity as well... it might be condensation?

author: MagicSmoker
author_rank: Super Contributor
timestamp: December 24, 2015, 04:05:51 pm
content: I think dexters_lab is onto something here - temp drops below dew point and you get condensation. Crystal oscillators have an annoying habit of misbehaving in such an environment.