Single Channel Temperature Sensors

Last modified by Microchip on 2024/10/14 08:38

Temperature Switches

Temperature switches offer excellent temperature accuracy (±1°C, typical), with a very low operating current of less than 25 μA. These devices can replace mechanical switches in a variety of sensing and control applications.

Voltage Output Temperature Sensors

Voltage output temperature sensors develop an output voltage proportional to temperature with a typical temperature coefficient of 6.25 mV/°C, 10 mV/°C, and 19.5 mV/°C respectively. These temperature-to-voltage converters can sense temperatures ranging from −40°C to 150°C and feature an offset voltage that allows reading negative temperatures without requiring a negative supply voltage. 

Resistance Temperature Detectors (RTDs)

RTDs are able to sense temperature with extreme accuracy, have consistent and repeatable performance and low drift error (−200°C to 1200°C). For precision, these sensors also require a linearization look-up table in the microcontroller due to sensor non-linearities.

Thermistors

Thermistors (−100°C to 150°C) are normally used for over-temperature shutdown purposes. Although not as accurate as some of the other temperature sensor solutions, thermistors are inexpensive and come in small packages. They are also nonlinear and require a temperature compensation look-up table.

Digital Output

Single-channel digital output temperature sensors offer excellent temperature accuracy (±0.25°C, typical) with a very low operating current (250 μA, typical). Communication with these devices is accomplished via an industry-standard System Management Bus (SMBus)-, I²C- or Serial Peripheral Interface (SPI)-compatible interface protocol as shown in Figure 1. These devices feature a fast conversion rate, with temperature resolution ranging from 0.0625°C to 0.5°C and some contain integrated Electrically Erasable Programmable Read-Only Memory (EEPROM) for customer preference storage and for datalogging.

Temperature Sensing Overview

Figure 1: Temperature Sensing Overview

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Multichannel Digital Temperature Sensors with Multi-channel Temperature Monitoring

In addition to local temperature sensing, Microchip offers digital temperature sensors with multi-channel TS Temperature monitoring channels. These devices offer excellent temperature accuracy (±0.25°C, typical) as well. The remote channels are inexpensively implemented by using Positive Negative Positive (PNP) or Negative Positive Negative (NPN) transistors connected to act as a diode. Analog filtering and resistance error correction allow for remote monitors to be placed several meters away from the Integrated Circuit (IC).

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Thermocouples

Thermocouples are usually selected because of their wide temperature range (−270°C to 1750°C), ruggedness and price. However, they are highly non-linear and often require significant linearization algorithms. Additionally, the voltage output of this temperature sensing element is relatively low compared to devices that can convert voltage signals to a digital representation, resulting in required analog gain stages in the circuit.

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Fan Controller

Fans are used in cases where heat needs to be dissipated faster than the natural surroundings would accomplish on their own. Microchip has several levels of fan control. For simple fan speed control shown in Figure 2, there are stand-alone Revolutions Per Minute (RPM) closed-loop controllers. For a full thermal management solution, many devices integrate temperature monitoring in addition to PWM control. Controllers also incorporate both spin-up and ramp rate control algorithms to minimize acoustics.

System Diagram

Figure 2: System Diagram

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