The Wireless Data Logger

Wireless Data Logger machine signal photocell

What does the future hold?

A wireless data logger is a device that can be purely electronic or microprocessor based, or even a mixture of the two.

A wireless data logger is just a data logger with a wireless link, or at least access to a wireless link, to the analyzing computer(s) part of the data logger system.

More and more data logging applications are making use of wireless links, so much so it's being sought after as the norm these days.

Machine/management information systems quite often will use a PLC as a data logger mainly for its robust construction and connect ability that's either built in or plugs via a module. This is quite a good choice because it's already well suited to the job it has to do in this application.

Its job is to record data and some in some applications it can be recording data very fast. Whether the data is digital, analogue or frequency would depend exactly what the data logger is designed for. A data logger can be just a small battery powered device or at the other end of the scale, a computer driven unit with its own power supply and battery backed UPS (Uninterruptible Power Supply).

Some data loggers are programmable as to how and what data is recorded. A wireless data logger is generally a two-part device consisting of a sensor assembly and recording unit and a display and analysing computer communicating together via a wireless link. This type of set-up is normally found in very harsh environments where the recorder section just wouldn’t be reliable.

There remains very little of a standard amongst data logger manufacturers – but having said that a number of data logger manufacturers are starting to give output in XML format file data. This is a good sign for the industry as up till now there has been very little compatibility with the recorded data formats.

Data logger, data logging and data acquisition.
The terms data logger or data logging and data acquisition are quite often used in each other’s place and most of the time are used to mean the same thing, but in historical terms they are different. Data loggers are data acquisition systems, but data acquisition systems are not necessarily, but could be, data loggers.

Let’s have a look at some of the features.

1. The sample rate that data loggers generally use is slower than that of a typical data acquisition system. A maximum sampling rate of 1 Hz (cycles per second) may well be considered quite fast for a data logging system. But this in turn could be considered slow for a data acquisition system.

2. Most of the time, if a reference is made to a data logger, people are talking about a stand-alone device, for example not connected to a computer. The computer is required to display and analyse the data of course but the data logger can stand alone recording data for downloading to a computer later on.

3. Data acquisition systems on the other hand need to be connected to a computer to gather information/data. This type of system is usually involved in doing much faster sample rates and shorter real time analysis periods.

4. Another major difference with the data-logging unit, it has memory built in to enable it to be stand-alone. Without built in memory the device would have nowhere to store the data it’s gathering. Which is a bit of a drawback if you’re a data logger, you’d be out of a job! In some instances this built in memory is very large indeed, this allows unattended data logging for long periods, such as weather stations and remote pipelines.

5. Some of the newer data logging equipment even have a web server built in and can be addressed from the WWW. This is getting very popular, as for example the weather station, would be able to be remotely accessed and monitored by numerous lots of people whom are interested in the results. (Well you wouldn’t look if you weren’t, would you?). This is the direction a lot of applications are going in now.

6. Data logger, wireless data logger and data acquisition systems would be expected to have a real time clock built in to be able to date and time stamp the information gathered. Even gathering data that’s not time sensitive would need to be time/date stamped to make comparison between other data from the same source, even if it’s just used for identification purposes. However most data loggers use the clock, on some units the amount this clock drifts over a month/year can be quite important.

7. A wireless data logger system would normal consist of a wireless data logger transmitter and an analysing computer receiver, the wireless bit would normally be referring to the link between the two. The wireless data logger system would be data logging with the computer off, but then may well change mode with the computer on to be more of a wireless data acquisition system. I think this is the best of both worlds, but that’s just me. The wireless data logger system link could be a low power local (200m or so) transmitter, a modem line with a dialler built in, a cell phone network connection or even a satellite terminal. These would all be for the remote collection of data and possible resetting of the data logger memory. Also maybe an alarm function for early warning system or the need for attendance.

8. The future of the wireless data logger evolving quite quickly nowadays, the notion of the stand-alone data logger or data acquisition system is changing into a multi function unit. A unit that can stand alone, is able to run fast data acquisition, has access to wireless link for alarms and automatic reporting of sections of data, also some (more expensive end) serving web pages, auto emailing and FTP their results directly into databases the end user accesses.

9. Just by the nature of what and where data loggers are used they must be extremely reliable and power efficient as a lot of them are run on batteries with solar or wind charging. In a machine information system running off a machine though, we don’t need to be that fussy about the power requirements.

Some applications the evolving wireless data logger is used for is included the following listing, but of course there hundreds of other situations and places they are used so it far from a limited list.

- Unattended weather stations, water condition recording.

- Gas pressure recording.

- Road traffic counting (I bet you thought it was a speed camera).

- Monitoring for maintenance applications (factory or otherwise).

- Educational purposes.

- Silo and tank level systems.

- Machine Information Systems (I had to get that in!).

- Nuclear power stations (but they won’t tell me how it’s used).

- Waste treatment plants (ha ha I didn’t want to know).

This is to name but a few applications that the wireless data logger could be, no probably is, fulfilling the needs of today. I'm sure you could think of dozens more but I’m also sure that’ll do from me for now.
Where ever data needs to be collected, equipment monitored, critical situations reported you will find the humble, efficient, reliable and getting smaller, wireless data logger.

So, going back to the question at the top, what does the future hold? I think the future is quite busy for the data logging animal, though it's probably going to the wireless species more in the future.

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