Data Logger / Introduction to Data Logging Devices

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. Most instrument manufacturers, however, consider a datalogger 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. When choosing a data logger the following parameters should be considered.

Choosing a Data Logger

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 a wide range of data loggers for several types of signals, including thermocouple, sound, pH, pressure and many more (see the "Types of Signal" for a list).

Number of Inputs

Data Loggers are available in both single and multi-channel designs. A 32 channels data logger such as OMEGA OM-SQ2040 Series is capable of handling multiple inputs.

Size

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.

Speed/Memory

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.

Choose the right Datalogger

Miniature Single Input Data Loggers

Miniature single input data loggers are generally low cost loggers dedicated to a specific input type. These types of data loggers are often used in the transportation industry. A typical application would be to include a temperature data logger in a shipment of food products to insure that the food temperature does not exceed acceptable limits. In addition to temperature miniature data loggers are available for a large variety of input types.

Fixed Mount Multi-Channel Data Loggers

Fixed input loggers have a fixed number of input channels which are generally dedicated for a specific type of input. OMEGA offers fixed input data loggers ranging from one to 8 channels. Data loggers can also be optionally equipped with an LCD display for displaying measured data in real time.

Handheld Multi-Channel Data Loggers

Handheld multi-channel loggers are commonly used in applications where the data logger is to be carried from one location to another. They are also commonly used in benchtop or laboratory environments. In addition to storing data internally some models even contain on board printers which can produce an immediate hardcopy of the data.

Modular Data Loggers

A modular data logger is configurable and expandable through the use of plug-in modules. The modules are normally field configurable and the user has the option of adding as many channels to satisfy the application requirement. These data loggers are often equipped with advanced functions and communication interfaces, such as the Ethernet interface or the wireless Wi-Fi interface.

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Frequently Asked Questions (FAQ)

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.

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