Selecting a Voltage Measurement Data Logger

Mainly used to observe or record waveforms that change at mid-speed, such as analog signals (e.g. vibrations) and equipment control signals (logic signals). These recorders are multi-functional (for example, they have insulation inputs), and many of them are specifically designed for voltage, vibration, control signals, and similar applications. If data collection is your main purpose, these recorders may have excessive performance and be too expensive compared to data loggers.

KEYENCE “NR Series” data logger

Capable of collecting various types of data, such as voltage and temperature, simultaneously and accurately from low- to mid- and high-speed using multiple channels.
This logger is highly scalable in combination with measurement units and is capable of collecting reliable data using its inter-channel insulation function, which is a big difference from general-purpose recorders.

KEYENCE data loggers, which satisfy recent needs and solve problems with conventional data loggers, enable you to:

• Use useful display and analysis functions built into the main unit.
• Communicate with your PC wirelessly or send data at high speed through compression of CSV files.
• Process collected data all the way up to analysis using the dedicated software.

Nowadays, attention is being paid to data loggers that are highly compatible with PCs and can drastically improve the efficiency of subsequent work.

If more channels may be required in the future, a modular data logger enables you to easily increase the number of channels simply by adding a measurement unit. This is economical because you do not have to replace the whole instrument.
Also, compared to channel extension with a high-performance, high-speed waveform recorder , a data logger is beneficial in its extensibility with a lower channel unit price while maintaining its high-speed sampling and high resolution.

For simultaneous measurement of multiple channels, the availability of the “inter-channel insulation (inter-CH insulation, or isolator)” function, which can reduce the effect of noise, is also an important point to consider.
Since most general-purpose recorders are not equipped with this insulation function, they may be affected by shifts in measured values or noise from other inputs during simultaneous voltage measurement. As a countermeasure against these issues, we recommend that you select a data logger equipped with the inter-channel insulation function.

It is necessary to clarify whether the fineness of the required measured values—that is, the “accuracy”—is the “minimum display digit” (the minimum digit you want to read) or the “absolute values.” The specifications required for an instrument vary depending on this.

• Minimum displayable digit = “Display resolution”
• Absolute values from which no further deviation occurs = “Absolute accuracy”

Once you clarify this, refer to the “measurement accuracy (accuracy)” for an instrument to check your required specifications.
The table below shows example specifications.

“F.S.” written on the Measurement accuracy row refers to “full scale.” In the above table, the measurable range for a measurement range of ±5 V is -5.0 to 5.0, the F.S. is 10 V V. You can see that the measurement accuracy is ±0.1% x 10 V.

Generally, there is a trade-off between the sampling speed (cycle) and the resolution. Even with the same measurement range, a lower resolution leads to a lower measurement accuracy. Therefore, it is important to select different instruments for different measurement targets. Also, note that an instrument that satisfies the needs of both accuracy and sampling speed tends to have a higher price.

Most data loggers only have simple indicators on the main units, and a minimal number of operation buttons is provided. Because settings and operations are assumed to be performed on PCs, the status of measurement is usually hard to understand on the main unit. This sometimes causes issues such as testing to be continued with no one recognizing that measurement has not been started.
You can prevent careless mistakes and improve your work efficiency by selecting a data logger that enables you to check the status of measurement and the measured data on the main unit monitor and also allows you to configure settings and perform operations easily without a PC.

The way the acquired data is saved is also important. Data can be saved not only in the storage (such as an HDD or SSD) built into the connected PC but also in the large-capacity CF memory card inserted into the data logger.
By simultaneously saving data in both the PC and the data logger (mirror saving), you can also improve the safety and reliability of data saving.

Most data loggers are mainly designed literally for “data logging.” This means post-processing with PCs, such as data collection and analysis, sometimes takes time and effort. However, you can greatly reduce the work hours by selecting a data logger that is highly compatible with PCs and Excel.

KEYENCE data loggers have been developed to maximize compatibility with PCs, with work efficiency taken into account.

• Enables easy connection to and detailed data display in the dedicated software.
• Reduces the data volume with the compressed CSV save function. Significantly reduces the time to send data to PCs.
• Drastically improves the efficiency of analysis on PCs with the dedicated analysis software.
• Greatly improves work efficiency, including direct data writing into Excel.

If it becomes necessary to move a data logger to use it in a different location, the problem of portability arises for large or heavy data loggers. Additionally, the question of whether power can be supplied by not only an AC power supply but also by a battery becomes important.

One method to employ in measuring data other than voltage is using external equipment to convert this data to voltage and employing dedicated data loggers for each of the other pieces of data. However, this method is very expensive because several instruments must be installed. It also raises problems such as complicated systems and wiring, finding ways to synchronize the data , and a lot of effort and man-hours required for management and processing of multiple pieces of data after measurement.

It is recommended that you select a multi-input data logger if it is likely to simultaneously measure data other than voltage.
A single data logger that can collect multiple types of data tends to be more expensive than instruments that record only a single type of data. However, when the purchasing of multiple converters and dedicated loggers is taken into account, the installation will result in almost the same cost.
Although the installation cost is almost the same, a multi-input data logger has the following advantages.

• Reduces post-measurement man-hours thanks to batch collection and analysis of multiple types of data.
• Reduces the number of wiring lines, which may cause problems, through concentrated equipment.
• Offers a mostly unified usage method, as well as smooth setup and troubleshooting.
• Easy to receive support because various input units are also provided by the same manufacturer.

Consider the scalability in channel extension. It is also important to use insulation to take measures against potential problems.

Clarify the definitions of accuracy and resolution to check your required specifications.

Easiness of settings, operation, and reading. Easy connection to PCs, data transfer/analysis functions, and compatibility with Excel directly affect post-processing man-hours.

Whether an AC power supply is always available and whether operation on battery power may be necessary.