10 Questions Before Buying a Data Logger

Fast data collection and retrieval for remote monitoring applications requires equipment tailored to your objective.

10 Questions Before Buying a Data Logger

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Remote monitoring applications in the water and wastewater industry often require close attention to detail. When purchasing a new data logging solution, it’s crucial to understand the exact capabilities and specifications of the device you need. However, the sheer variety of data loggers and data logging systems can often make it difficult to choose the best model for your application.

To help guide you through the multitude of consider-ations, applications specialists from CAS DataLoggers have outlined a list of 10 questions to ask when purchasing a data logger for a remote monitoring application:

1. According to Pete Martin, sales manager for CAS DataLoggers, “To begin searching for the right product, always keep in mind your starting point — what do you want to accomplish? Consider whether you need a quick fix for a specific problem or a long-term solution providing a general need with room for expansion. With such a wide range of options open to you, details such as knowing how many and what types of inputs are required along with how often readings need to be taken (determining the logger’s sampling rate) are critical. Often users believe they need to record multiple channels of data at hundreds of Hz, not realizing that this will soon exceed the logger’s available memory and require more frequent downloads.”

2. You’ll also want to take into account whether the data logger must be equipped with external sensors or utilize built-in sensors for temperature or humidity. Will the logger need to perform real-time calculations on the measured data or will it need to provide some type of alarm notification? Will the device need output signals to alert users or connect to other equipment? Having a clear initial idea of what requirements are needed and what features might become necessary in the future are key factors in making the most suitable choice.

3. The type of sensors being recorded is also critical in the decision process. Ideally, the data logger will have the versatility to accommodate the wide range of sensors you may need to connect it to. For instance, if you’re planning to use thermocouples, the logger must support TC inputs. Likewise, if the application must accommodate several different inputs (including 4-20 mA current loops, voltage, digital pulses, etc.) then you’ll require a more flexible data logger with universal inputs. Determining the number and type of inputs to adequately monitor your conditions is critical.

4. Most data loggers can record at a rate up to about 1 Hz (once per second), although many faster recording frequencies are available. When speaking with a representative, it’s important to determine the right recording rates for your application. When recording from a K-type thermocouple, for example, the sensor/sample may take several seconds to change temperature, making a high-sample device give you redundant data. Depending on the application, it may only be necessary to capture a few minutes worth of data or you may need to store entire months of readings. This can be easily determined the amount of data storage required by multiplying the number of channels by the sample rate and recording duration, given in this quick formula:

Total number of points = number of channels x sample rate x recording duration

Since model specifications vary, there may be a limit based on the total amount of internal memory, or the data logger may offer the option of using external memory such as a USB memory stick to expand the available memory. Options like these can significantly cut down your costs.

5. Where are you planning to use the logger? If the logger is going to be used in the field, you’ll definitely want to consider a ruggedized device that offers a wide range of operating temperatures and can survive hazardous working conditions including dust and dirt.

Depending on your application, you may need to safely enclose the logger in a sturdy industrial or portable enclosure. Also, decide how often you need to transport the data logger. Will it be mounted in an enclosure on a pole, or does it need to be moved between jobs, which could jostle an unprotected unit and reduce its longevity? Will it be installed in a vehicle? These questions will help you determine the best way to protect your investment. Will it be installed in a vehicle? These questions will help you determine the best way to protect your investment.

6. If this is for remote monitoring, how will the logger be powered? Is there AC power at the site or will you need a solar panel or battery-operated device for extended operation? Systems such as the Infinite ADU provide very low power operation allowing extended operation — up to 5 years — from a single Li battery.

7. Does the system need some sort of local display? Some data loggers have a built-in LCD display with a backlight that shows status and measurement data whether in dim lighting, underground or outdoors. This will be especially helpful when commissioning the system, instructing personnel in its use, or looking at live data in the field.

8. Is this going to be a permanent installation with static requirements or do you anticipate the need to expand to add more inputs or sensors in the future? If you anticipate future expansion or possibly re-using the logger after the project is complete, search for data loggers with a modular design so you can expand or add other capabilities when needed.

9. How remote is the location where you’re collecting the data? Is the logger in an area where it’s not practical to use a computer to connect and download data? If you just need to download data, a data logger with support for a USB memory stick serves as the fastest way to get your data. Communication with the data logger for setup, monitoring and downloading data can be done in many different ways. While a USB connection will require you to be within 10-15 feet of the logger, Ethernet or Wi-Fi can provide access from across the plant. If the location is remote and lacks network infrastructure, a model with a cellular modem can provide access almost anywhere. This solution can help you avoid the time and cost of traveling to gather real-time data from remote sensors, instruments and control systems.

10. When it comes to software, look for a user-friendly interface that enables an easy setup. Many loggers come with free software for configuration, monitoring and data retrieval.

“Above all, go with the capabilities which prove the most practical for your application and analysis,” Martin says. “If you’re looking for data trends, we recommend that you use the statistical capabilities offered by certain data loggers to summarize the data over an interval. If you’re looking for anomalies, use the triggering features in many data loggers to simply capture a window around the event. All of these features and more are available to ensure that your logger handles every aspect of your application.”

In addition to the typical requirements for a regular in-house data logging project, the issues around power and data retrieval are really critical when the logger is going to be located miles away in the middle of a field.


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