Fluke 961B Temperature and Humidity Data Logger with External Probe

A. Product Overview

The Fluke 961B is a professional temperature data logger developed for applications requiring continuous and traceable temperature monitoring over a wide range. Its external PT100 platinum resistance sensor allows it to measure temperatures from minus 85 degrees Celsius to 150 degrees Celsius, making it suitable for both ultra-low-temperature and high-temperature monitoring applications.

The logger features a clear LCD screen that allows users to view the current temperature, minimum and maximum recorded values, logging status, alarm status, date, time, battery condition and the number of stored readings without connecting the instrument to a computer.

The Fluke 961B can store up to 32,000 temperature readings. Its logging interval can be adjusted from 10 seconds to 24 hours, supporting both short-term testing and long-duration monitoring.

Recorded data can be downloaded by connecting the logger directly to a computer through its built-in USB plug. The device can automatically generate a PDF report without requiring software. FlukeLog software can also be used for advanced configuration, graphical analysis, historical data management and exporting reports in PDF, Excel and TXT formats.

Main Features

• External PT100 platinum resistance temperature probe
• Temperature range from minus 85 degrees Celsius to 150 degrees Celsius
• Temperature resolution of 0.1 degrees Celsius
• Storage capacity of 32,000 readings
• Adjustable logging interval from 10 seconds to 24 hours
• Immediate, button-operated and timed start modes
• Button-operated, software-controlled and stop-when-full options
• Multiple high and low temperature alarm limits
• Single-event and cumulative alarm operation
• Stop-when-full and circular logging modes
• Direct USB connectivity
• Automatic PDF report generation
• PDF, Excel and TXT report formats
• Password protection for settings and data access
• Event-marking function
• Large LCD display
• IP65 dust and water resistance
• One-metre drop-tested construction
• CR2450 replaceable battery
• Approximately one-year battery life under specified conditions

B. Working Principle

The Fluke 961B works through an external PT100 platinum resistance temperature sensor. A PT100 sensor changes its electrical resistance in a predictable manner as the temperature changes.

The logger measures this resistance, converts it into a corresponding temperature value and records the reading with its date and time. The measurements are stored automatically according to the logging interval selected by the user.

Before monitoring begins, the Fluke 961B can be connected to a computer and configured through FlukeLog software. The user can set:

• Logging interval
• Logging duration
• Immediate, button or timed start
• Start delay
• Stop method
• Temperature alarm thresholds
• Alarm delay
• Single or cumulative alarm type
• Temperature correction value
• Circular logging preference
• Trip number and description
• Time zone
• Password protection
• PDF report generation

After configuration, the external PT100 probe is placed at the required measurement point, such as inside a freezer, refrigerated compartment, cold room or temperature chamber.

The logger continuously measures and records temperature values. If a reading remains above or below a configured limit for the selected alarm-delay period, the device records an alarm event and provides an alarm indication.

When monitoring is complete, the Fluke 961B can be connected directly to a computer. The recorded PDF report can be opened from the logger without specialised software. FlukeLog software provides additional functions such as graphs, statistical analysis, historical data storage and Excel or TXT export.

C. Why the Fluke 961B Is Used

The Fluke 961B is used when temperature conditions must be continuously monitored, recorded and documented.

Manual temperature checks only show conditions at a particular moment. They may not detect temperature fluctuations that occur between inspections. A data logger records measurements automatically over time, making it possible to identify short temperature excursions, gradual changes and equipment failures.

The Fluke 961B helps users:

• Monitor ultra-low-temperature freezers
• Verify cold-chain conditions
• Record temperature during transportation
• Detect temperature excursions
• Maintain traceable storage records
• Monitor laboratory refrigerators and freezers
• Support cold-room validation
• Investigate product spoilage or quality complaints
• Verify refrigerator and freezer performance
• Generate records for audits and quality reviews
• Analyse temperature trends
• Confirm whether storage limits were maintained
• Identify refrigeration system problems
• Reduce the risk of damage to temperature-sensitive products

Its extended range makes it particularly useful for applications that cannot be covered by standard ambient-temperature data loggers.

The automatic PDF function also simplifies reporting because the user can retrieve a structured temperature report directly through USB without installing additional software.

D. Suitable Buyers

Pharmaceutical Companies

The Fluke 961B is suitable for monitoring pharmaceutical cold rooms, ultra-low-temperature freezers, medicine storage facilities and temperature-controlled shipments.

Vaccine Storage Facilities

It can be used to maintain temperature records for vaccine freezers, refrigerated storage units and distribution operations.

Cold-Chain Logistics Companies

The logger can record temperature conditions inside refrigerated trucks, reefer containers, cooler boxes and insulated transportation packages.

Laboratories

Research, medical, testing and calibration laboratories can use it for monitoring freezers, refrigerators, sample-storage areas and environmental chambers.

Hospitals and Healthcare Facilities

It is suitable for monitoring medicines, biological materials, diagnostic samples and temperature-sensitive medical supplies.

Food Processing and Storage Businesses

Food manufacturers, cold-storage operators and distributors can use it to monitor frozen products, chilled goods and temperature-controlled warehouses.

Biotechnology Companies

The Fluke 961B can support temperature monitoring for biological samples, reagents, research materials and laboratory storage equipment.

Calibration and Validation Service Providers

It is suitable for temperature mapping, cold-room validation, freezer studies, transportation validation and storage-condition verification.

Refrigeration Service Companies

Technicians can use the logger to analyse the performance of freezers, cold rooms, refrigerated cabinets and refrigeration systems.

Industrial Manufacturers

Manufacturers can use it for process-temperature recording, equipment testing, environmental chambers and temperature-controlled production areas.

Frequently Asked Questions

1. Does the Fluke 961B measure humidity?

No. The Fluke 961B measures temperature only. It uses an external PT100 temperature probe and does not have a humidity sensor.

2. What is the temperature range of the Fluke 961B?

The temperature measurement range is minus 85 degrees Celsius to 150 degrees Celsius.

3. What type of sensor does the Fluke 961B use?

It uses an external PT100 platinum resistance temperature sensor.

4. What is the temperature accuracy?

The stated accuracy is plus or minus 0.3 degrees Celsius plus 0.005 multiplied by the absolute value of the measured temperature.

5. What is the temperature resolution?

The Fluke 961B has a temperature resolution of 0.1 degrees Celsius.

6. How many readings can the logger store?

It can store up to 32,000 temperature readings.

7. What logging intervals are available?

The logging interval can be configured from 10 seconds to 24 hours.

8. Does the Fluke 961B require software to download data?

No. A PDF report can be opened directly after connecting the logger to a computer through USB. FlukeLog software is required for detailed analysis, advanced settings and Excel or TXT export.

9. What report formats are supported?

The logger supports direct PDF reports. FlukeLog software can also export recorded data in Excel and TXT formats.

10. Can the Fluke 961B monitor ultra-low-temperature freezers?

Yes. Its lower measurement limit of minus 85 degrees Celsius makes it suitable for many ultra-low-temperature freezer applications.

11. Does it have configurable alarms?

Yes. It supports up to three upper temperature limits and two lower temperature limits.

12. What is the difference between single and cumulative alarms?

A single alarm is triggered when one continuous temperature excursion lasts for the configured alarm-delay period. A cumulative alarm adds together the duration of multiple temperature excursions and triggers when the total time reaches the configured limit.

13. What is circular logging?

Circular logging allows the logger to overwrite the oldest readings and continue recording when the memory becomes full.

14. Can the logger stop automatically when its memory is full?

Yes. Circular logging can be disabled so that the instrument stops recording when all 32,000 memory locations have been used.

15. Can the monitoring start automatically?

Yes. The Fluke 961B supports immediate start, button start and timed start modes.

16. Can users mark important events during logging?

Yes. An event can be marked manually during recording for easier identification during later data analysis.

17. Is password protection available?

Yes. A six-character password can be configured to protect logger settings and data access through FlukeLog software. Direct PDF reading does not require the password.

18. Is the Fluke 961B waterproof?

The instrument has an IP65 rating, which provides protection against dust and water jets. It is not designed for continuous immersion.

19. Which battery does the Fluke 961B use?

It uses one replaceable CR2450 battery.

20. What is the expected battery life?

The stated battery life is approximately one year when recording at a 15-minute interval at 25 degrees Celsius.

21. Can data be downloaded while the logger is recording?

Yes. Data can be downloaded while logging is in progress or after logging has stopped.

22. What is the difference between the Fluke 961A and Fluke 961B?

The Fluke 961A uses a built-in digital sensor and measures both temperature and humidity. The Fluke 961B uses an external PT100 probe, measures temperature only and provides a much wider temperature range.