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HOBO · Data Logger, Temperature and Humidity, USB
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A compact USB logger measuring 3.44 by 1.44 by 0.6 inches with a one year battery, intervals from 1 second to 18 hours, a programmable alarm, a humidity range of 15 to 95 percent, a temperature range of minus 4 F to 158 F, IP50 protection, a user replaceable RH sensor and HOBOware required to configure and read it. The specification sheet is unusually complete. It also shows that the stated accuracy of plus or minus 3.5 percent RH applies only from 25 to 85 percent, which is narrower than the range the logger will display.
The range and the accuracy are not the same interval
Two figures sit a few words apart in the specification dump and they are easy to read as one. Relative humidity range 15 to 95 percent. Accuracy plus or minus 3.5 percent RH from 25 to 85 percent RH.
So the instrument will report a value anywhere between 15 and 95, but the manufacturer only claims a tolerance between 25 and 85. Outside that band there is a number on the screen and no stated confidence in it.
This is not a flaw and it is not unusual. Capacitive humidity sensors genuinely are less predictable at the dry and wet extremes, and a manufacturer who specifies the honest band is being more informative than one who prints a single accuracy figure across the whole range. It is worth praising rather than criticising.
What it does mean is that you have to check the band against your job, and the jobs that fall outside it are not exotic. A paper or instrument store held deliberately dry sits near or below 25 percent. A subfloor, a cellar or a wall cavity under investigation for damp sits above 85 percent, which is usually the entire reason for deploying a logger there. In both cases the readings are indicative and the tolerance is unstated. Our explainer on accuracy against precision covers why this distinction changes what a record can prove.
The replaceable sensor is the real signal
Listed under special features is a single phrase: user replaceable RH sensor. It tells you more about this product than any other line.
Humidity sensing elements drift. They age, they are affected by contamination, and after a few years a reading that was within tolerance is not. On a sealed consumer logger that is terminal. The device keeps working and keeps being wrong, which is the worst of both outcomes.
A replaceable element changes the economics and the trust. A drifted logger is restored with a part rather than discarded, and an owner who suspects drift has a way to resolve the suspicion. Instruments designed for people who care about the number get this feature. Instruments designed to be looked at do not.
The one year warranty and the stated United States country of origin sit in the same frame. This is positioned as equipment rather than a gadget.
One second to eighteen hours is a very wide span
The logging interval range is 1 second to 18 hours, and the two ends serve completely different purposes.
At one second intervals you are capturing an event: a door opening, a defrost cycle, a kiln ramp, the effect of switching extraction on. Memory fills quickly at that rate, so this is for short deliberate captures.
At eighteen hours you are capturing a season. Deploy it in a cellar and leave it, and the battery figure of one year becomes the relevant constraint rather than the memory. Four readings a day for months is how you establish whether a space has a humidity problem or had a bad week.
Most useful work sits between: five or fifteen minute intervals over a few weeks answers almost every building question. The point of a wide span is that one instrument covers both the event and the season, and a programmable alarm means it can also tell you when a threshold was crossed rather than leaving you to find it in the data.
The full published specification
| Specification | Published in the listing |
|---|---|
| Humidity range | 15 to 95 percent RH |
| Humidity accuracy | Plus or minus 3.5 percent RH, from 25 to 85 percent RH only |
| Temperature range | Minus 4 F to 158 F |
| Temperature accuracy | Not stated in the listing bullets |
| Logging intervals | 1 second to 18 hours |
| Battery life | One year, no AC adapter |
| Protection | IP50, dust protected, no water protection |
| RH sensor | User replaceable |
| Alarm | Programmable |
| Interface | USB, HOBOware or HOBOware Pro required |
| Remote probe | No |
| Size | 3.44 by 1.44 by 0.6 inches |
| Origin and warranty | United States, one year |
The absent temperature accuracy is the gap that matters most, because this is sold as a temperature and humidity logger and only one of the two has a tolerance. If the temperature record is the one you will act on, that figure needs establishing elsewhere before you rely on it.
IP50 deserves emphasis because of where loggers get put. Dust protected, water not protected. A crawl space at 90 percent humidity is acceptable. A crawl space where water drips is not, and neither is an unsheltered outdoor position. With no remote probe option, the sensor goes where the body goes, so protecting one means enclosing both.
Who this is for
This is for someone who needs a defensible record rather than a reading: a surveyor documenting a damp investigation, a conservator watching a store, a facilities engineer proving a space held its conditions. The replaceable sensor, the programmable alarm, the honest accuracy band and the one year battery all point that way.
It is the wrong choice if you want to glance at a display, because the data lives in software. It is the wrong choice for wet or exposed positions without an enclosure, because IP50 says so. And if your target conditions are below 25 or above 85 percent humidity, understand that you are working outside the band the manufacturer stands behind, which is exactly the situation a damp investigation puts you in.
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Frequently Asked Questions
Why does the accuracy range differ from the measurement range?
Because a humidity sensor is least reliable at the extremes and manufacturers specify where they are willing to stand behind it. The listing states a range of 15 to 95 percent RH and accuracy of plus or minus 3.5 percent RH from 25 to 85 percent RH. Between 15 and 25 and between 85 and 95 the logger still reports a number, but no tolerance is claimed for it. If your interest is a very dry store or a damp subfloor, that is precisely the region with no accuracy statement.
What is a user replaceable RH sensor worth?
It extends the useful life of the instrument. Humidity sensing elements drift and eventually fail, and on most consumer loggers that is the end of the device. The listing states a user replaceable RH sensor as a special feature, which means a drifted logger becomes a working logger again rather than waste. This is a professional instrument trait and it is the clearest signal of what class of product this is.
What does IP50 permit?
Dust protection and no water protection at all. The fifth digit zero is explicit about that. A data logger is often deployed somewhere humid, and humid is fine, but condensation, splashing and rain are not. For a damp crawl space or an outdoor position it needs an enclosure.
Do I need the software?
Yes. The listing states software required and compatibility with HOBOware or HOBOware Pro. The logger is configured and read through the vendor application, so your records live inside that ecosystem. For long term archiving, export rather than relying on the application database.
Is there a temperature accuracy figure?
Not in the listing. It publishes a temperature range of minus 4 F to 158 F and an accuracy figure for humidity only. For a device sold as a temperature and humidity logger that is a notable omission, and if the temperature reading is the one you will act on, establish the tolerance before buying.
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