Digital temperature sensors offer high accuracy

By Gina Roos, editor-in-chief

Texas Instruments (TI) has unveiled a new temperature sensor family that offers ±0.1°C accuracy across a wide temperature range with zero calibration during manufacturing, simplifying system design for industrial and medical applications. The TMP117 sensors expand TI’s portfolio of digital temperature sensors that enable designers to integrate thermal monitoring into their designs.

The TMP117 offers Class-AA resistance temperature detector (RTD) accuracy for industrial applications. It provides a direct readout of temperature, with no additional linearization or acquisition error, and maintains accurate temperature over a wide range as follows:

• ±0.1°C from –20°C to 50°C
• ±0.15°C from –40°C to 50°C
• ±0.2°C from –40°C to 100°C
• ±0.25°C from –55°C to 125°C
• ±0.3°C from –55°C to 150°C

At a similar level of accuracy with a platinum RTD, “engineers must select a multitude of precision components, simulate and fine-tune the circuit, carefully lay out the PCB to avoid impedance mismatches, develop software to linearize the output, and calibrate each system,” said TI. The TMP117 is claimed to be the first single-chip temp sensor to offer similar performance to platinum RTDs without the extra development work, which reduces design complexity and power consumption.

TI also offers the TMP117M digital temperature sensor, which supports requirements for medical thermometers. For medical applications, the TMP117M provides ±0.1°C accuracy from 30°C to 45°C, said TI, and supports American Society for Testing and Materials (ASTM) E1112 and International Organization for Standardization (ISO) 80601 requirements for patient thermometers.

The TMP117 and TMP117M target ultra-low-power patient monitoring, field transmitter, and metering applications. The devices, which consume only 6.3 μW, are said to cut power usage by up to 95% compared to a typical RTD measurement system, enabling designers to meet tight power budgets in field transmitters and battery-powered applications, said TI. In addition, the low power consumption reduces the impact of self-heating, enabling more accurate temperature measurement. The sensors are I² C- and SMBus-interface– compatible.

The TMP117M digital temperature sensor for medical applications is available now in volume quantities and is priced at $2.44 in quantities of 1,000. Pre-production samples of the TMP117 are now available through the TI store and are priced at $1.60 in quantities of 1,000. Both devices will be available in six-pin WSON no-lead packaging. An evaluation board (TMP117EVM) is available. Click here for the datasheet.