In the first of this mini blog series, we learned about the most common and costly mistakes you can make with sonde calibration.
As a quick recap on how to avoid mistakes while calibrating, make sure you:
- Don’t use expired standards
- Read standard labels carefully
- Clean your equipment thoroughly before calibrating
- Avoid taking shortcuts in calibration like skimping on rinsing
- …And if you’re not sure which standards and calibration points to use, try to get a better read on your monitoring location – if all else fails, calibrate over the full range of the sensor
Okay - so now that you’ve got calibration under control, let’s move on to the next mistake often made with sondes – incorrect setup or configuration.
Common, Costly Mistake #2:
Incorrect Setup (Continuous Monitoring)
Last year, we surveyed sonde users across the globe, posing the question: “What is your greatest challenge as a monitoring organization?” The top response was data loss.
A few check boxes can really make a big difference. Setting up a sonde incorrectly can lead to a host of problems, including lost data or incomplete data records. This is a monitoring organization’s worst enemy because there’s no way to rewind time to know what happened at your site.
With new technology like EXO, we’ve streamlined the number of settings required to get your equipment up and running. Eliminating potential for errors during instrument setup was a key point of emphasis for us. With other sondes however, there are numerous options and menus for determining how an instrument collects data in the field. Setup is often complicated and navigating your way through the software can be tricky. Let’s go through a few hurdles in the setup process to help you avoid problems with your deployment.
Incorrect Deployment Settings
When you’re preparing a sonde for a long term deployment out in the field, there is an entire section of the software package dedicated to this application. For continuous monitoring, you’re typically setting up a sonde system to connect up to a data logger or data collection platform, and the sonde has to communicate and transfer the data it collects up to the data logger via SDI-12 protocols.
This handoff of information between the two pieces of equipment is where problems can happen.
A common mistake people make is data logger configuration. Be sure the parameters you set to log on your sonde match up with those to be received by the data logger program. Even the order is important here.
To ensure that data will always be collected, YSI recommends using redundant logging in the sonde as well as the advanced deployment setting, Sample and Hold. With internal logging and Sample and Hold turned on the sonde, a copy of the data is saved onto the sonde’s internal memory, and an additional copy is sent up to the data logger. You can turn on this feature on a 6-Series sonde by navigating to the Advanced>Setup menu and activating it. On EXO, this is in the Advanced tab of the Deployment Setup. This can at least give some peace of mind should you run into any issues with the rest of your monitoring setup, that you still have the data you need.
Choosing an Inappropriate Sampling Interval
When you’re not attaching a sonde up to a data logger as just discussed, premature battery depletion can also result in data loss. Most sondes will estimate a deployment time based on remaining battery voltage. As a point of reference, EXO sondes will log data for up to 90 days at a 15 minute sampling interval in water temperatures around 25ºC.
Battery life should be an important consideration when choosing a sampling interval. When a sampling interval is shorter than 2 minutes, it’s possible that a sondes’ wipers won’t have adequate time to wipe the sensor surfaces to clear them from biofouling or sediment. In these high temporal resolution applications, a manual wipe command may be needed to activate wiping.
A 10 or 15 minute sampling interval is common for long-term baseline monitoring and will work in 80% of applications.
Incorrect Start Time
Once you’re ready to go and you’ve finalized your sonde’s deployment settings, the software prompts you to choose when the equipment should start collecting data. This is the last step in the process and is also one of the easiest to mess up. One typo here and all the work up to this point in calibrating and preparing your sonde for the field was for nothing.
People take advantage of the ability to enter a custom start time for their sonde deployments. It allows them to prep the sonde in advance of a site visit and there’s a convenience factor to it. The problem is, with one keystroke December 3rd, 2014 can easily turn into a start time of December 3rd, 2015 and then the sonde never starts logging data. Two months later when you collect the instrument from the field, and there’s nothing there, all because of something so simple. This problem can also crop up with custom deployment times if your sonde clock isn’t set to the correct time as well.
To avoid these mistakes, and to have some peace of mind that your equipment is in good, working condition – tell your sonde to “Start Now” or “Start at the Next Interval” , and deploy it in your lab or office overnight. Just place it in an aerated bucket, nothing special and check it the next day. Not only are you making sure you’ve set the instrument up correctly, but you’re collecting QA data for the upcoming deployment which you can use to check for sensor drift in your data later down the road.
After your mock deployment in the office, if you’re satisfied that the sonde is good to go, head out to the field site. The sonde will continue collecting data along the way, but when looking at the data you’ll always know when the sonde hits the water because your conductivity readings will be dramatically different in air than in water.
To summarize what we’ve talked about here:
- If you’re setting up a sonde for long term deployment or continuous monitoring – check that your sampling interval and battery life are adequate for your monitoring goal.
- If you’re connecting the sonde to a data logger, be sure to setup the RS232/SDI-12 settings in the software and that those settings match those of the data logger device.
- Be careful when choosing a start time for a deployment, because one typo can lead to an incomplete data set.
To learn more about correct setup for continuous monitoring, check out EXO University, for on-demand training on our to properly set up your sonde.
Additional Blog Posts of Interest:
5 Tips To Prevent Costly Mistakes With Your Sondes | Tip 1 of 5
10 Tips to Prevent Biofouling on Water Quality Instruments
Trouble Collecting Data with Your Water Quality Sonde? Try This!
Webinar: Expert Tips for Continuous Water Quality Monitoring | YSI, Aquatic Informatics and Pennsylvania DEP