NTC thermistors and analog temperature sensors are two common temperature sensing solutions for most electronic applications. Deciding which technology is best for your application is a difficult task. However, I will tell you why some of the NTC thermistors should be discarded and the analog temperature sensor is used.
Figure 1 shows the comparison of output voltage and temperature. Note that the NTC thermistor requires a resistor network to help linearize its output. This is because their resistance vs temperature characteristics vary exponentially. Unlike NTC thermistors, analog temperature sensors do not require any additional components because they have a virtual linear output voltage. For example, at a full operating temperature range of -50 ° C to 150 ° C, Texas Instruments' LMT87 analog temperature sensor provides a virtual linear output voltage for the entire device.
As can be seen from the three NTC thermistor curves shown in Figure 1, you can adjust the position of the linear portion of the curve by changing the value of the bias resistor. Note that this is a limited range and the curve begins to saturate at low temperatures and high temperatures. When an ADC is connected, this saturation can cause a temperature error if the resolution of the ADC is not high enough to detect a change in the output voltage per degree Celsius. As a result, NTC thermistors tend to be less accurate over the full operating temperature range and typically require higher resolution ADCs.
Figure 1 Relationship between output voltage (V) and temperature (°C)
Figure 2 shows the relationship between supply current and temperature. The LMT87 is typically 5.4μA with a maximum of 9μA. NTC thermistor networks tend to consume more power because their supply currents are much stronger and vary with temperature. Note that if you increase the resistance of the bias resistor, the supply current of the NTC thermistor network is reduced. But remember to also choose a bias resistor to ensure that the output voltage vs. temperature profile is linear over the expected temperature range. This type of compromise and balance is not required when using analog temperature sensors because they have a very constant low supply current and a virtual linear output voltage. Another disadvantage of NTC thermistors is that engineers must consider the self-heating effect because it causes other errors.
Figure 2 Relationship between supply current (μA) and temperature (°C)
By abandoning the NTC thermistor and switching to TI's easy-to-use analog temperature sensor, you can avoid many NTC thermistor design issues.
Author: Texas Instruments Brian Gosselin
This article is taken from the July issue of the "Electronic Technology" special issue of the electronic enthusiast network 
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Rotary Switches
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The Electrical Rotary Switch is a switch that controls the opening and closing of the main contact by rotating the handle.There are two types of Rotary Switches, namely a unipolar unit structure and a multi-pole multi-position structure. Unipolar unit rotary switches are often used in conjunction with rotary potentiometers in applications, while multi-pole multi-position rotary switches are often used for switching of operating line.
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