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Portable Temperature/Humidity Data Loggers with USB Interface


Item# OM-141

Volume discounts available
Volume Discount Schedule
Quantity Price each
1-4 C$128.80
5-9 C$122.36
10-24 C$119.78
25-49 C$114.63
50-99 C$112.06
100+ C$109.48

In stock

Lead Time (If not in stock): 26 weeks
Portable Temperature/Humidity Data Loggers with USB Interface OM-141 OM-141
  • One Button Starts/Stops Data Logging Without a PC
  • Plug-and-Play USB 2.0 Interface No Need for Cables, Cradles or Docks
  • Large Storage Capacity: 16,000 Pairs of Temperature and Humidity Readings
  • 3½-Digit LCD Displays Real-Time Temperature and RH Readings, Device Working Status and “Memory Full” (OM-143 and OM-144 Only)

OM-141 Model Options

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Edit these specs to order a different model. Not all combinations are valid. Options compatible with previous selections will be in bold.

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Measurement Type
Number of Measurements
Input Type
Maximum Samples
Data Interface
Max Sampling Rate

The OM-140 Series are low-cost, compact, battery powered temperature/humidity data loggers capable of unattended logging (recording) of the ambient temperature and relative humidity (RH) of an environment for days, weeks or months. The OM-144 data logger can also measure and optionally log surface temperatures spot-checked by a technician using the unit’s integral infrared (IR) thermometer. In addition, these units can also calculate and display absolute humidity levels in units of grains per pound (GPP) or g/kg. Also called mixing ratio, GPP is a more useful moisture metric than RH to water damage restorers. Using RH alone, a restorer might unknowingly introduce moist air—with a low RH but a high GPP—during a job’s drying phase.

Data logging can be started or stopped by pushing a button on the unit, eliminating the need to bring a laptop to the job site. After a data log has been captured and stored, it can be uploaded as a .txt file to any PC running the Windows® XP/7 or 8 operating system after plugging the data logger into one of the computer’s USB ports. The data logger’s internal flash memory is large enough to store 16,300 pairs of temperature and RH readings or for the model OM-144 nearly 10,000 sets of RH, ambient temperature and surface temperature readings. Included with the product is a mini-disc with the drivers needed to interface the unit to the computer, as well as software that can display a data log file as a table or graph and/or export it to Microsoft Excel. Exporting to Excel is recommended for sophisticated trending and analysis of humidity and temperature data and easy detection of unexpected excursions.
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Rated 5 out of 5 by from So Far So Good Been using two of these units for the past couple weeks and they are performing well. Temperature accuracy is as advertised (they give the exact same reading to the tenth of a degree C and these temps match other accurate devices I have. The relative humidity values vary by 0.5%, but this is in the advertised range. Very easy devices to set-up and to remove data..
Date published: 2016-12-26
Rated 4 out of 5 by from Great value. Excellent product. After 2 weeks of testing I'm going to give the OM-141 4 stars. If I could give it a 4.9 I would do that. I've only had one problem so far and it is not a showstopper. I initially set the sampling rate to 30 seconds to collect and simulate a collection of many data-points, way more than we need), and in one week it had collected more data than the software seemed to download without a 'timeout' error being thrown. There needs to be a way to set the timeout value. When I put these in production we will set the sample rate to 12 hours, more than adequate for our needs, but I'd like to only download the data when I receive an alarm. if my freezers are doing well, I can foresee a timeout occurring if the time between downloads is sufficiently long to record a bunch of data-points. In device setup, the sensitivity of the slider to set High/Low points is way too sensitive and I end up setting bounds slightly different from what I want. Not a big deal, but frustrating. As I explore the software I am continually surprised by how many features are available. The best advice I can give to new users of the products is to "Read the **** manual". Another problem we experienced had nothing to do with the device, but rather it was cockpit trouble: when we placed two of the device, I forgot to hit the start-button. I don't know what the solution would be on the OM141 to protect us from operator (me) error. Add that to your "would be a nice feature to have" list.
Date published: 2018-02-20
Rated 1 out of 5 by from Thermometer and RH with data log portable It takes too long to changes in temperature. I regret purchase. Software to retrieve data is troublesome as well. I don’t recommend it.
Date published: 2023-07-27
Rated 3 out of 5 by from OK for low budget I wish I had purchased the 143. The 141 is hard to tell if it's Power On or Not.
Date published: 2018-09-08
Rated 1 out of 5 by from Frequent software malfunctions Purchased 4 of the base models of the OM-141. They worked the first time, well within advertised accuracy. Additional setups and data extraction work 10% of the time. Package software often has timeout errors even with small <100 data point sets. Frequently wipes data off devices for no reason as well. Manual and setup DVD provided no explanations for these peculiar cases
Date published: 2017-08-31
Rated 4 out of 5 by from great features I bought this instrument a couple of weeks ago and its very helpful to monitor our ac performance data.
Date published: 2017-07-23
Rated 5 out of 5 by from Great out the box Tested over and hour and checked. So far so good. Fixing to put them to work on mold lawsuit home and will follow up after recording for three weeks
Date published: 2017-07-19
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The OM-140 series (141;142;143 and 144) are they suitable for the monitoring of ventilation temperature into the undergound mines ?

Asked by: Diak
Thank you for your question. We will require more information to help on this question, please email the DAS team at DAS@OMEGA.COM
Answered by: Application Engineer PV
Date published: 2023-09-23

I use Linux, not Windows. A few Qs: 1. What is the default setting for sampling rate? 2. Will the device appear as a storage device if plugged into a Linux kernel? 3. If yes to 2., will the .txt data file appear on the device? Thx

Asked by: Cam W
Thanks for your questions. Unfortunately, the OM-141 (or the OM-HL-SP) will not support Linux since both logger&rsquo;s software is designed for Windows. However, we can recommend the product OM-HL-SP, the max logging rate is 1 sec and the default is set to 60 secs. Please contact us anytime with further questions.
Answered by: Jane
Date published: 2019-05-15

Regarding the OM-141 temperature/RH datalogger software, is it available for download as an alternative for laptop PCs without a CD drive?

Asked by: AnthonyM
Thank you for your question. ELUSB V2.04 software is available as a download from OM-141 product page. Just scroll down under manuals and downloads there will a software download.
Answered by: Application Engineer PV
Date published: 2022-09-22

I see the data sheet says these work with Windows&reg; XP/7 or 8 operating system. Will these work with Windows 10?

Asked by: CAVB
At the time it is only tested to work with operating systems up to Windows 8
Answered by: JA Engineer
Date published: 2022-10-18

Are these NIST calibrated, because the product details do not mention that. If not, what would be the cost of getting it calibrated?

Asked by: Krutarth
Thank you for your question. The OM-141 is not available with Nist Please consider OM-EL-USB-2-PLUS which is available with Nist. I have attached 2 links from our website with details and pricing.
Answered by: Application Engineer PV
Date published: 2023-02-08

Would this device be compatible with any type of probe . we are currently loooking for a device to measure compost temperature and humidity via some kind of probe. Thank you !

Asked by: Marc Andre Lauzon
Hello Marc As long as it is one of the following thermocouple types: J, K, T, E, R, S, B, C or N Also the probe will need either a standard round prong or mini blade type connector attached at the end so it can connect to the transmitter.
Answered by: JA Engineer
Date published: 2019-08-28
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