What Is a Temperature Data Logger? Types and Selection Criteria
A temperature data logger records temperature measurements from one or many points in its memory with date and time and transfers the record to a computer.
A temperature data logger is a device that records temperature measurements from one or many points in its memory with date and time and transfers the record to a computer. Multi-channel benchtop models are used in heating tests of electronic boards, panels and devices and in mapping the temperature distribution of ovens and moulds; USB types are used to monitor warehouse and shipment temperature.
Types of temperature data loggers
| Type | How it works | Models in the catalog |
|---|---|---|
| Multi-channel thermocouple logger | Benchtop, mains-powered; measures many points at the same time via thermocouples, shows them on the display and records them | UNI-T UT3208+ (8 channels), UT3216 and UT3216+ (16), UT3232 (32), UT3240+ (40, LAN) |
| USB temperature logger | Runs on a coin cell and records the temperature where it is left; read by plugging it into a computer over USB | UNI-T UT330T |
The two types do not replace each other: a multi-channel logger measures external points via thermocouples, while a USB logger only records the temperature where it sits.
Selection criteria
- Channel count: Add spare channels to the number of points you will measure at the same time. The multi-channel models in the catalog have 8, 16, 32 and 40 channels.
- Thermocouple type: The product data lists support for types J, K, T, E, S, N, B and R. Type K is general purpose; at very high temperatures the platinum-based types R, S or B are used. The type setting on the device must match the thermocouple connected.
- Measuring range: The stated range of -200 °C to 1800 °C depends on the thermocouple type; the reachable limit is set by the thermocouple you connect, not by the device.
- Resolution and accuracy: According to the product names, the UT3240+ has 0.01 °C and the UT3216 0.1 °C resolution. Resolution is the smallest step on the display, not accuracy; the total error is the device error plus the thermocouple tolerance.
- Interface: The product data lists RS-232 and USB interfaces and SCPI command support; the UT3240+ is read over the network via LAN. For long tests, check the interface and software for live transfer of measurements to a computer.
- Logging interval: Choose a short interval for a fast heating test and a longer one for a test lasting days; plan to transfer the record before the memory fills.
Common mistakes
- Extending a thermocouple with copper cable: The extension must be made with thermocouple compensation cable of the same type; otherwise the cold junction moves to the joint and the reading is off by the temperature difference between the joint and the instrument terminals.
- Reversing polarity: The reading falls as the temperature rises; connect the plus and minus leads according to the input markings on the device.
- Fixing the thermocouple tip loosely to the surface: In surface measurement the tip must be in full contact with the surface; secure it with heat-resistant tape or adhesive.
- Attaching a thermocouple to a live part: Do not measure at an energised point without checking the channel-to-channel isolation and the grounding of the device in the datasheet.
Related standard
- IEC 60584-1: Thermocouple types (J, K, T, E, N, R, S, B) and voltage–temperature tables.
Temperature data loggers in the catalog
The Temperature Data Loggers category has 6 active products, all from Unit (UNI-T): UT3208+, UT3216, UT3216+, UT3232, UT3240+ and UT330T. The multi-channel models are priced on quotation and the UT330T is listed with a price. If humidity is to be recorded along with temperature, see Temperature and Humidity Data Loggers; for thermocouples and probes, see Temperature Probes.
Frequently asked questions
Which thermocouple can be connected to a multi-channel temperature logger?
A thermocouple of a type the device supports and that suits the measuring temperature; the models in the catalog support types J, K, T, E, S, N, B and R. Each channel's type setting is made according to the thermocouple connected.
Are resolution and accuracy the same thing?
No. A resolution of 0.01 °C shows the smallest step on the display. How close the measurement is to the true value depends on the accuracy of the device and the tolerance of the thermocouple.
What is the difference between the UT330T and a multi-channel logger?
The UT330T is a battery-powered single-point USB logger that is left inside a warehouse or shipment. The multi-channel models are mains-powered and measure between 8 and 40 points at the same time via thermocouples.
How is a thermocouple cable extended?
With extension or compensation cable of the same type as the thermocouple, observing polarity. At an intermediate joint, a thermocouple connector of the same type is used.