Campbell Scientific’s met station features make integration a breeze
By: Adam Baker
Today I’ve got meteorological stations on the mind. A few days ago, a customer called up and said the data they were getting from their back of module temperature sensors wasn’t what they expected. It didn’t correlate with what they thought real-world conditions were.
I looked into the situation, and it turns out the temperature coming in wasn’t scaled properly, so it was under-reporting the temperature.
That mistake got me thinking about met stations more broadly, and what types of met stations I’ve seen work well over my years in utility-scale solar. As a systems integrator, there are definitely some I prefer to work with over others.
A great example of one of the better met stations I’ve had luck with is Campbell Scientific.
Some off-the-shelf SCADA providers may have three or four separate interface devices to collect signals from met station instruments. Speaking from experience, managing 3 or 4 different devices is problematic. Instead, you can use a Campbell Scientific met station to unite different devices.
I like the Campbell Scientific datalogger base met station, and here are three reasons why:
Ability to Control the Datalogger
Unlike most met stations, you can build logic into the data collection algorithm.
We have an application where we pull data from a bunch of 4-20 milliamp sensors once every 5 minutes. We don’t want to continuously supply loop power from the battery of the met station, so we built logic into the datalogger to turn on a 24v signal to power RDT transmitters and bring the data in for a short period of time, then shut everything off so we can extend the system’s battery life.
Another way I’ve used the datalogger’s logic engine is when I’m using pyranometers. Some customers want to have a ventilator and heater inside to get good thermal stability and keep airflow inside the dome so it doesn’t accumulate dust.
The problem is, the heater and the ventilators take up energy. In the instance where the 24v power supply goes off because of a maintenance issue or short site outage, the datalogger is able to detect that a condition has occurred. It stops the heater and ventilator from operating while the system runs on battery power, which provides a longer battery life of the system. If we had the heaters and ventilators on during that outage, we would only have about two or three days of run life.
No Messy Unit Conversions
Unlike most met stations, you can instantly and internally convert incoming signals into engineering units for easy implementation into SCADA
For example, a pyranometer gives me a millivolt signal. There’s a correction factor and calibration sheet that comes with the pyranometer that describes how to correctly multiply values to get engineering units. The problem is, doing that during post processing is subject to errors (such as making sure that the right calibration factor is applied with the right device).
If you do the calculations within the datalogger itself, a wizard allows you to put in the calibration factor directly. You don’t have to figure out how to do the math to convert from millivolts to degrees, or watts per square meter.
If there’s ever a loss of network communications, Campbell Scientific’s met station saves and logs data for later retrieval. It can log in a few ways. It logs locally to a card, makes the data available via MODBUS, or it can even transmit data via DNP3.
You want to know when a sample was taken? DNP3 communications allow you to take the values along with the time they were generated and bring that back into your SCADA system. You might be able to do some correlations that you wouldn’t be able to do if you just had an analog data device that pulled values into the SCADA system for datalogging and later manipulation.
Say you decide to plug in a compact flash card. We typically use one that reads up to 16 GB of memory, which is probably 10-15 years’ worth of data storage. If you lose communications to the device, you can easily recover the last two years of data right off the data card inside the datalogger, bring it back to the office, and conduct analysis.
Campbell Scientific Met Stations Make Integration Easy
There are no instruments we can’t pair with Campbell Scientific’s met station and dataloggers. We get excellent support because they’re based in the United States. That means getting equipment overnighted is never a problem. I’ve never found an instrument I couldn’t use with this datalogger.
Adam Baker is Senior Sales Executive at Affinity Energy with responsibility for providing subject matter expertise in utility-scale solar plant controls, instrumentation, and data acquisition. With 23 years of experience in automation and control, Adam’s previous companies include Rockwell Automation (Allen-Bradley), First Solar, DEPCOM Power, and GE Fanuc Automation.
Adam was instrumental in the development and deployment of three of the largest PV solar power plants in the United States, including 550 MW Topaz Solar in California, 290 MW Agua Caliente Solar in Arizona, and 550 MW Desert Sunlight in the Mojave Desert.
After a 6-year stint in controls design and architecture for the PV solar market, Adam joined Affinity Energy in 2016 and returned to sales leadership, where he has spent most of his career. Adam has a B.S. in Electrical Engineering from the University of Massachusetts, and has been active in environmental and good food movements for several years.