Product type
A wireless data logger records measurements at a point where no wiring runs, and moves them to somewhere a person or a system can read them. The measurement itself is the easy part; what decides the instrument is the journey the data takes, because a logger that cannot be reached produces a record nobody sees until it is too late to act on.
A wireless data logger records measurements at a point where no wiring runs, and moves them to somewhere a person or a system can read them. The measurement itself is the easy part; what decides the instrument is the journey the data takes, because a logger that cannot be reached produces a record nobody sees until it is too late to act on.
The radio link can be arranged in more than one way. A logger can talk directly to a gateway within its range, join an existing site network, or carry its readings to a server over a wide-area connection. Each of those imposes different demands on range, power and infrastructure, and the choice is usually made by the site rather than by the instrument.
The second deciding figure is power. A logger on a mains supply can log and transmit as often as it likes; one running from a battery has to ration both, and the interval it can sustain is the product of how often it measures, how often it sends, and how far the radio has to reach. Everything else about the instrument is secondary to those two questions.
A wireless logger is a measuring front end, a processor and a radio sharing one enclosure, with a memory between them. The front end conditions the signal from a sensor; the processor scales it and applies the logging interval; the memory holds readings between transmissions so that a lost message is not a lost measurement. That store-and-forward behaviour is what separates a logger from a transmitter: the record survives a gap in the link.
The radio link is asymmetric in its demands. Transmitting costs far more energy than measuring, and the energy cost rises steeply with distance and with the amount of data sent. A design that sends one short reading an hour can run for years on a small battery; one that sends a burst every minute draws the same battery down in weeks. The topology follows from the same constraint: a short hop to a nearby gateway is cheap, while a long reach to a distant base station is not.
What the record is for decides how it should be read. A log kept to show that a limit was respected has to be complete and time-stamped, and it needs a clock and a storage medium able to hold the whole period. A log kept to trigger an alarm has to arrive while the event still matters, which puts the emphasis on the link rather than on the memory. An instrument that does both carries a clock and a store, and the timestamp becomes as important as the measurement.
Most of the specification is fixed by these decisions rather than by the accuracy class. Each one constrains the next, which is why they are settled in order.
| Configuration | Options to fix | What it actually decides |
|---|---|---|
| Radio technology and topology | A short-range link to a local gateway, a site network, or a wide-area cellular connection | How far a reading has to travel, and what infrastructure already exists between the logger and the reader. |
| Number of loggers per receiver | Each logger talking directly to the reader, or several loggers relaying through a gateway | How many points one receiver can serve, and how the cost of coverage scales with the size of the site. |
| Power source | A replaceable battery, a rechargeable battery, or a mains supply | The interval the logger can sustain, and whether the site can provide power at the measuring point. |
| Logging and transmission interval | How often the sensor is read, and how often the reading is sent | Battery life and the resolution of the record: a short interval shows the shape of an event, a long one only its average. |
| On-board memory | The number of readings held between transmissions, and whether a removable card is accepted | Whether the record survives a break in the link, and how long the logger can be left unattended. |
| Inputs and channels | The signal types accepted, their count, and whether they are isolated | Which sensors can be connected directly, and how many points one instrument covers. |
| Enclosure and rating | The protection against water and dust, and the operating temperature range | Where the logger can be mounted, and whether it will survive the environment at the measuring point. |
| Timestamping and clock | Whether readings carry a time from a synchronised clock | Whether the record can be used as evidence, which depends on the time and the value being tied together reliably. |
| Factor | Why it decides the answer | How to settle it before enquiring |
|---|---|---|
| Where the data has to end up | A local reader, a plant system and a remote server impose different links | State where the readings are to be seen, and by whom. |
| Distance and obstruction | Radio range is reduced by walls, metalwork and process equipment | Describe the path from the logger to the receiver, and what stands between them. |
| Interval required | A short interval improves resolution and shortens battery life | State how often a reading is needed, and how quickly an event has to be noticed. |
| Battery life expected | It follows from the interval and the transmission distance | State how long the logger has to run between battery changes. |
| Sensors to be connected | The front end decides whether a sensor connects directly | List the signal types and the number of points. |
| Environment at the point | Rating and operating temperature decide whether the unit can be mounted there | State the conditions at the measuring point. |
| Record and evidence | A complete, time-stamped record is a different requirement from a live reading | State whether the data has to be retained and produced as evidence. |
If any of these are still open, send what is known. A quotation can be issued against a duty description and refined once the gaps are filled.
These are the types an enquiry for a wireless data logger usually turns out to be, and the point at which the choice is genuinely decided.
| Nearest alternative | What separates it from a wireless data logger |
|---|---|
| Data loggers | Store readings at the point of measurement and are read by visiting them or by collecting a memory card. They are simpler and cheaper where the point is accessible and the data is not wanted until later; the wireless logger buys the ability to read it without going there. |
| Industrial data loggers | Accept process signals directly in a panel or an enclosure and are wired into the installation. They suit a plant room where cabling is straightforward, while the wireless logger is chosen precisely where running that cable is the problem. |
| Temperature data loggers | Are specialised to one parameter and often to a specific sensor, which makes them simple and inexpensive in a cold-chain or validation duty. A wireless logger is chosen where several quantities are involved, or where the record has to be live rather than downloaded. |
| Remote monitoring systems | Include the collection, storage and presentation of data from many points as a system, rather than a single instrument. Where the requirement is a view of a whole site, the system is the answer and the loggers are components of it. |
The commonest error here is buying on the number of channels or the logging interval without settling the link. A logger that measures everything and reaches nothing produces a record that is discovered too late to act on.
The first reply can be a quotation rather than a set of questions if the enquiry carries these. Where a figure is not known, send the duty description and we will confirm what it implies.
Available products
ESPC3-20 (2 models) · Wireless Data Loggers
Two-port wireless serial data logger that records equipment traffic to a TF card and serves live and historical logs over Wi-Fi, with UDP and MQTT reporting.
Also in Data Acquisition & Monitoring
Every type we quote for under Data Acquisition & Monitoring. A type with no link yet is still quoted for - it is described on the Data Acquisition & Monitoring overview, and gets a page of its own as soon as a model is published against it.
Frequently asked
Obstruction more than distance. A free path between two points gives a range measured in hundreds of metres or more, while the same equipment separated by a steel wall, a concrete floor or a rack of pipework may barely reach across a room. Metal reflects and absorbs the signal, and the reflections arrive at the receiver out of step with the direct path. The practical answer is to site a gateway in the same space as the loggers rather than to judge by the advertised figure.
It follows from the interval and the transmission distance rather than from the battery alone. Transmitting draws far more energy than measuring, and both the number of transmissions and the power needed for each one shorten the life. A logger sending an hourly reading to a nearby gateway can run for years; the same unit sending every minute to a distant receiver may not last a month. An honest figure is only available for a stated interval and distance.
They are held in the on-board memory and sent when the link returns, provided the logger stores before it transmits. That is the reason to check the size of the memory against the interval and the longest expected outage: a store that holds a day of readings covers a daily interruption, and one that holds an hour does not. A logger that transmits and discards loses exactly the period when something was wrong.
It needs something to receive the data. Some instruments connect directly to an existing site network or to a server over a wide-area link, in which case no separate gateway is required; others rely on a short-range link to a gateway that then forwards the readings. Which applies is settled by what already exists at the site and by how far the data has to travel, rather than by the logger alone.
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