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How do you tell if a faulty thermistor?
While some people use a much more exhaustive and precise testing procedure, a very simple test can uncover the most common problems with a thermistor: * measure the resistance of the thermistor at room temperature with an ohmmeter. If this resistance is 0 (short) or infinity (open), then something is connected incorrectly or the thermistor has been destroyed. (These are the most common problems). If that test looks good, then a followup test can uncover nearly all the remaining possible problems with a thermistor: * put icewater in a ziplock bag and press it against the thermistor. Then measure the resistance of the themistor at freezing. The two measured values of resistance are usually adequate to identify what kind of thermistor it is. If both values are practically the same, then it's not really a thermistor -- perhaps someone has accidentally substituted a resistor. If one or both values are not the expected values, perhaps someone has accidentally substituted a different kind of thermistor.
What does a thermistor do that makes it different from a thermocouple?
a thermistor is a temperature sensitive resistor - to measure temperature you must measure its resistance and convert that resistance to equivalent temperaturea thermocouple is a temperature sensitive voltage source(i.e. battery) - to measure temperature you must measure the voltage across it and a reference thermocouple at a known constant temperature connected in series with it and convert that voltage to equivalent temperatureNote: Thermistors do not require reference thermistors, thermocouples do require reference thermocouples at a known constant temperature. Thermocouples are more linear than thermistors, making them easier to read accurately. Thermocouples are available that are far more sensitive to small changes in temperature than thermistors.
What is the significance of the constant temperature reference in ohms law?
As temperature affects resistivity, the resistance of a conductor may change if its temperature is allowed to increase. For pure metal conductors, the resistance generally increases as the temperature increases.Ohm's Law ('the current flowing along a conductor, at constant temperature, is directly proportional to the potential difference across that conductor') only applies when the resistance of the conductor is constant so, when verifying Ohm's Law, the temperature must be kept constant, in order to keep the resistance constant.It should be pointed out that the ratio of voltage (U) to current (R) is called resistance (R), and the resistance of a circuit can be found from the equation, R = U/I whether Ohm's Law applies or not -but Ohm's Law itself only applies when the ratio is constant over a range of voltage variation.
What voltage does a Resistor temperature detector put out?
None. An RTD is a passive device. It changes resistance as the temp varies. Your circuit must basically measure the resistance to determine temp. There are many different types of RTD's, each with it's own temperature curve.
How many meters of wire make one ohm?
The resistance (ohms) of a conductor depends on a number of factors including the type of material, its thickness and the temperature. There are charts that will tell you the resistance of different sizes of wires and the correction factor to use for non-standard temperatures.
