What is a Data Logger?
Technically speaking, a data logger is any device that can be used to store data. This includes many data acquisition devices such as plug-in boards or serial communication systems which use a computer as a real time data recording system. However, most instrument manufacturers consider a data logger a stand alone device that can read various types of electrical signals and store the data in internal memory for later download to a computer.
The advantage of data loggers is that they can operate independently of a computer, unlike many other types of data acquisition devices. Data loggers are available in various shapes and sizes. The range includes simple economical single channel fixed function loggers to more powerful programmable devices capable of handling hundreds of inputs.
Choosing a Data Logger
When choosing a data logger the following parameters should be considered.
- Input Signal
OMEGA offers data loggers that are compatible with most types of signals. Some data loggers are dedicated to a certain input type while others are programmable for different types of inputs. OMEGA offers data loggers for the following types of signals.
AC Voltage/Current Light On/Off Shock/Acceleration Bridge/Strain/Load/Pressure Motor On/Off Sound Dew point PH Pressure Temperature Event or State Process Voltage/Current Thermistor Frequency Relative Humidity Thermocouple Level RTD
- Number of Inputs
Data Loggers are available in both single and multi-channel designs. Some data loggers are capable of handling hundreds of inputs. OMEGA’s OMB-LOGBOOK-300 for example is expandable to over 400 channels.
In many applications space is a limitation. In those cases the size of the data logger may be a critical selection parameter. OMEGA’s OM-CP family of data loggers are extremely compact and include models for most input types.
In comparison to real time data acquisition systems, data loggers generally have low sample rates. This is normally because they store data in internal memory which is limited. The higher the data rates the more memory required. Therefore when specifying a data logger it is important to determine the sample rate and the sample duration which can be used to calculate the required memory. For example. If an application requires sample rates of 1 per second and the test must last one hour, the data logger must be able to store 3600 samples(1 sample/sec x 1 hour x 3600 seconds/hour).
- Real Time Operation
In some applications it may be desirable to display the data being collected in real time on a computer. Certain data loggers such as OMEGA’s OM-CP family support this feature.
Data Logger Frequently Asked Questions(FAQ)
Why Choose a Data Logger Over Other Types of Data Collection Instruments?
Three types of instruments are commonly used for collecting and storing data. They are 1)Real-Time Data Acquisition Systems, 2)Chart Recorders and 3)Data Loggers
Data loggers are normally more economical than chart recorders. They offer more flexibility and are available with a greater variety of input types. Most data loggers collect data which may be directly transferred to a computer. Although this option is available with some recorders, it normally adds significant expense to the recorder price.
Data acquisition systems offer a great deal of flexibility and are certainly attractive when high sample rates are required, however, since they require connection or installation into a computer, the computer must also be present and active when collecting the data. Data loggers can collect data independently of a computer. Data is normally collected in non-volatile memory for later download to a computer. The computer does not need to be present during the data collection process. This makes them ideally suited for applications requiring portability.
Do Data Loggers Need to be Connected to a Computer?
No, some data loggers provide an option for real-time display but all OMEGA data loggers collect data independently of the computer.
What is the Maximum Sample Rate for a Data Logger?
The sample rate depends on the specific model. Although most data loggers have a maximum data rate of 1 or 2 samples per second, OMEGA offers a number of data loggers that can sample in excess of 100 samples per second.
How are the Data Loggers Powered?
Most data loggers are battery powered some also offer an option for external power.
How Long Does the Battery Powered Logger Last?
The battery life of a data logger depends on a number of parameters including the specific model and sample rate. In general the faster the sample rate the shorter the battery life. Many OMEGA data loggers feature a battery life as long as ten years.
Will the Data Logger Loose its Data if the Power or Battery Fails ?
Most OMEGA data loggers use non-volatile memory for data storage. This means that the data will not be lost if the power fails.
How Long Can the Data Logger Record Data?
The recording duration is dependent on the memory capacity of the data logger and the desired sample rate. To determine the duration divide the memory capacity(number of samples the device can record) by the sample rate. As an example assume that a given data logger can store 10,000 samples. If it is desired to record 2 samples every minute, the data logger can run for 10,000/2 or 5,000 minutes(about 3.5 days). If the sample rate was cut in half(1 sample per minute), the recording period would double to 7 days.