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Compact Portable USB Data Loggers

Portable Temperature Data Loggers


Item# OM-91

Volume discounts available
Volume Discount Schedule
Quantity Price each
1-4 $132.20
5-9 $125.59
10-24 $122.95
25-49 $117.66
50-99 $115.01
100+ $112.37

In stock

Lead Time (If not in stock): 5 weeks
Portable Temperature Data Loggers OM-91 OM-91
  • Models for Temperature (OM-91) and Temperature/Humidity (OM-92)
  • Immediate, Delayed (Specific Date/Time) or Pushbutton Start
  • Real-Time Mode
  • User-Configurable High and Low Alarms

OM-91 Model Options

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

The OM-90 Series are portable, battery operated, temperature (OM-91) and temperature/humidity (OM-92) data loggers. The OM-90 Series data loggers offer accurate and repeatable logging for temperature and relative humidity. Temperature is measured to an accuracy of ±0.3°C over the range of 5 to 60°C (41 to 140°F) and ±2.0°C over the full range of -30 to 80°C (-22 to 176°F). Relative humidity is measured to an accuracy of ±3.0% RH over the 20 to 80% RH range and ±5.0% RH over the 0 to 100% RH range. Both temperature and relative humidity are logged at a user configurable logging rate which is software selectable.

These data loggers are ideal for transportation applications where it is necessary to document that the material in-transit has stayed within particular environmental limits. High/low alarm limits can be set above or below which LED indicators will be activated so that the user can become aware that the desired transportation conditions have been exceeded.

Each data logger can be assigned a 16 character name. This can be helpful in applications where multiple data loggers are used and there is a need to distinguish between them (for example based on location).

The data logger includes a very easy to use software application. The application is used for configuration of the logger, extraction of logger data, graphically viewing data, spread sheet analysis of data and saving data to file (typically in comma separated value CSV file format) for third party applications such as Microsoft Excel. The graphical user interface is completely intuitive in terms of configuring new devices and extracting data from a field device. When the user has multiple devices requiring the same setup then a logger setup from a saved configuration file can be preloaded into the application to help expedite the process and ensure all loggers get setup identically. The application does not require any driver installations to connect to the data logger. Just install the software, run it and then connect the data logger.

    Range: -30 to 80°C (-22 to 176°F)
    Resolution: 0.01°C
    Accuracy: ±0.3°C from 5 to 60°C (41 to 140°F)
    Calibration Accuracy @ 25°C ±20°C: ±0.1°C
Humidity (OM-92 Only)
    Range: 0 to 95% RH
    Resolution: 0.01% RH
    Accuracy: ±3% over 20 to 80% RH range; ±5% RH below 20% RH or above 80% RH
    Calibration Accuracy @ 25% RH: ±1.8% RH @ 25% RH
    OM-91: 65,520 temperature measurements
    OM-92: 65,520 temperature and 65,520 humidity measurements
Start Modes: Immediate start on disconnect from PC, delayed start (scheduled date/time) or pushbutton start
Recording Mode: Stop on memory full; when data logger operation is start/stopped by user intervention via button press, last memory location is retained
Recording Interval: 1 sec, 10 sec, 30 sec, 1 min, 10 min, 30 min, 1 hr (software selectable)
Software Compatibility: Windows XP/Vista/7, 8 & 10 (32-bit and 64-bit)
Real Time Logging: Displays real time data when connected to a PC
Real Time Clock: Time automatically synced to PC
Battery Backup: Continues to keep time when off
Accuracy: 0.50 sec/day (~3 min/year)
Alarms: High and Low alarms for temperature and humidity; dedicated alarm LED indicator
LED Indicators: Alarm and status LEDs
Device ID: Each data logger can have a 16 character name assigned
Connections: USB-C port
Power: 3V lithium CR2450 battery included (user replaceable)
Battery Life: Over 4 year battery life while logging
Bypass Mode: Unit is powered from USB when connected to conserve the battery
Dimensions: 53 H x 33 W x 15 mm D (1.38 x 2.36 x 0.6')
Weight: 25 g (0.9 oz)
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Rated 1 out of 5 by from Good product, crappy customer service I bought two dataloggers that were supposed to measure temperature/humidity but when I got them it only measured temperature. The specs were misleading. I called to try and return the two to get the two I needed and was told there were no refunds. I didn't want a refund, just to get the product I thought was sold. It's really disappointing they wouldn't offer me a replacement, so I will be taking my business to another company that will benefit from the additional 7 dataloggers I need to purchase. You lost money by having poor customer service.
Date published: 2024-02-27
Rated 4 out of 5 by from Small, easy to use dstalogger Ok data logger, but not robust. It does the job and the software is quick and easy to use.
Date published: 2023-10-08
Rated 5 out of 5 by from Great track record as reliable and accurate. Excited to use my new loggers! We've used these for many evaluations with success.
Date published: 2023-09-27
Rated 5 out of 5 by from Portable Temperature and Humidity Data Loggers Easy to set up and use. Software has good graphing output with Excel file export for further data analysis.
Date published: 2021-03-12
Rated 5 out of 5 by from Very Good Data Logger Pros: Small but accurate. Software comes free with logger and very easy to use. Cheap compared with competitor. NIST certificate available. Cons: Software does not work with multiple loggers.
Date published: 2020-07-13
Rated 1 out of 5 by from disappointing 1. I was not able to download the software. The quick start guide had a web address for the software that you cannot go to. I had to request help in an email. 2. Now that I have the software, the software does not connect to the om-92. No blue square even though my computer shows the om-92 connected and the software is open. Why is that? No troubleshooting guide. 3. I go to replace the battery, which the quick start guide says is a CR2450, so I buy a CR2450. When I get home and take the cover off, the battery is a CR2032 inside. Why does your guide say CR 2450 when your instrument uses CR2032?
Date published: 2020-06-07
Rated 4 out of 5 by from Reliable products Works great. Good quality products. We purchase from Omega all the time.
Date published: 2018-09-18
Rated 5 out of 5 by from Easy to set up and use The software is simple to use, and set up of the data logger is very easy. Compact device will suit my needs, and the USB will allow easy download of the temperature data.
Date published: 2018-03-22
Rated 5 out of 5 by from Graph is awesome! Have had it running 2 weeks. Tracks time & temp with a daily print-out!!!!Thanks
Date published: 2018-02-15
Rated 4 out of 5 by from Great little device I really find this small device handy to monitor the temp and %RH in my environmental chambers. The only thing that i find strange is the real time termperature data is higher than the remote temperature. Maybe the ICs in the unit are heating up during real time operation? I'm still trying to figure this out. But aside from the realtime readings this unit is accurate and works perfectly for my setup! Great device for the price!! I haven't used the tech support but I might give them a try to assist me with the realtime readings.
Date published: 2017-12-31
Rated 5 out of 5 by from Just what we needed I bought this device to monitor the conditions in a museum. It works well since we can move it around to different locations. It is simple to use and the software is excellent, self-explanatory, and offers useful options.
Date published: 2017-09-09
Rated 5 out of 5 by from Easy to Use! Bought 9 loggers from Omega. Super easy to use and works great! Have had no issues with them so far.
Date published: 2017-08-25
Rated 4 out of 5 by from Cute little bugger. Does a nice job but does not have a display so you have no feel for the temp trends until you dump the data from the logger into your computer. Nice graphics and can dump into an excel file so you can manipulate the data six ways 'til Sunday. Overall it does what it was intended to do. But a display would be a nice addition.
Date published: 2017-08-19
Rated 5 out of 5 by from Great temp/humidity monitor Had it over a year. Used initially to monitor a fridge while dry aging beef. I use vista and it will see the unit as long as the battery is good. Nice piece of mind to know that the temp of the fridge didn't change during my 60 day age. Used it a year later (needed a new battery so 4 years, yeah right...guess again) to compare the temp/humidity of the fridge with a pepsi cooler I got. The pepsi cooler is much more stable in temp/humidity. Aging beef, here we come again! Woo hoo! and I wont stink up the house this time!
Date published: 2017-07-02
Rated 5 out of 5 by from Excellent Excellent Excellent Excellent Excellent Excellent Excellent Excellent
Date published: 2016-07-29
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