Some applications of NTC thermistors for the measurement and control of temperature and other quantities
Reviewed by: Isabelle
On: 15 Jun, 2017
Viewed:227 times - 7 hour, 39 minute, 28 second ago
Downloaded: 0 times -
Rated 4 / 5 based on 387 reviews
The circuit in Figure 2. 17a is suitable for measuring a temperature over a limited range, for example, that of cooling water in cars. It consists of a battery, a series adjustable resistor, a thermist...
The circuit in Figure 2. 17a is suitable for measuring a temperature over a limited range, for example, that of cooling water in cars. It consists of a battery, a series adjustable resistor, a thermistor, and a micro ammeter. Curr ent in the circuit is a nonlinear function of the temperature because of the thermistor, but the scale of the micro ammeter can be marked accordingly.
Figure 2. 17b shows a thermal compensation application. In this case the aim is to compensate for the undesired temperature sensitivity of a copper- wire galvanometer. The copper temperature coefficient is positive. The ser ies addition of a resistor with a negative temperature coefficient results in the overall circuit exhibiting a negligible temperature coefficient. The function of the resistor shunting the thermistor will be described in the next section.
Figure 2. 17c shows a simple way to perform a temperature-dependent control action. When ambient temperature rises above a given threshold, the thermistor resistance decreases enough to allow the flow of a current capable of switching the relay. The adjustable resistor permits modification of the switching point.
The circuit in Figure 2. 17d can control liquid level. The supply voltage must be high enough to heat the thermistor well above the ambient. When the liquid level reaches the thermistor which it cools, its resistance increases in value and the current is reduced, thus switching the relay.
The circuit in Figure 2.17e is intended for time delay. The relay does not switch until the thermistor is hot enough to allow a higher current to flow.
Figure 2.18 shows several applications suggested for a switching PTC. In Figure 2. 18a it is used for starting a single-phase motor. When the switch is first closed, the PTC has a low resistance and allows a high current to flow through the starting coil. When the PTC heats because of the current, its resistance increases to a very high level, thus reducing the current to a very low value.
The circuit in Figure 2. l8b is usually used for automatic degaussing, for example, in color TV sets. In these units a high degaussing current must flow when first turned on, and then it must reduce to a low value.
Transient suppression when a switch opens is useful to reduce both cont act damage and transient propagation to any nearby susceptible circuits. When the switch is opened in the circuit in Figure 2. 18c, the PTC offers a low resistance because no current was flowing through it. But as time passes, its resistance increases, and most of the power stored in the inductive load is dissipated in it instead of being dissipated in form of an arc between switch contacts.
Figure 3.3a shows the simplest signal conditioning for a potentiometer having a nominal resistance R. The linear or rotary movement from the device to be mea...
Figure 3.1. It consists of placing a known stable resistor in series with the unknown one. First a reading is taken across that resistor and then another reading across the unknown one. Afterward t...
A temperature in the range from 30°C to 40°C is to be recorded using a recorder that accepts a full-scale voltage of 100 mV. The probe chosen is based on linearized thermistors for which ma...
Another parameter to be taken into account in LDRs is that their rise time, when illuminated, and their fall (or extinction) time, when darkened, are different and depend on both the material and t...
A magnetic field applied to a current-carrying conductor causes deviation of some electrons from their path. In addition to the Hall voltage (Section 4.3.2), there is a current decrease, which resu...
To obtain this expression, we did not use any mathematical model for RT. Thus this method can also be applied to PTC thermistors and other nonlinear resistive sensors.
As the fastest growing demand of circuit and wiring diagram for automotive and electronics on internet based on different uses such as electronic hobbyists, students, technicians and engineers than we decided to provide free circuit and wiring diagram base on your needed.
To find circuit and wiring diagram now a day its easy. E-learning through internet as a right place to search an exact circuit and wiring diagram of your choice and it's much fun and knowledgable. On internet you will find thousands of electronic circuit diagrams some are very good designed and some are not. So you have to modify them to make them according to your needs but some circuits are ready to make and require no changes.
There are many categories of circuit and wiring diagrams like automotive, audio circuits, radio & RF circuits, power supply circuits, light circuits, telephone circuits, timer circuits, battery charger circuits etc. There are many types of circuit and wiring diagrams some are very easy to build and some are very complicated, some are so small and some contain huge list of parts.
We provides free best quality and good designed schematic diagrams our diagrams are free to use for all electronic hobbyists, students, technicians and engineers. We also provides a full educational system to students new to electronics. If you are new to electronics you are a student or a electronic hobbyist and want to increase your knowledge in electronics or want to understand electronics in a very easy way so this is the right place for you we provide electronics beginner guide tutorials to easily understand complicated electronic theory. Our mission is to help students and professionals in their field.