How to use a multimeter to convert a thermal resistance signal into a rough temperature
Commonly used pointer multimeters and digital multimeters can roughly estimate the approximate temperature range of the thermal resistor.
Commonly used thermal resistors include (P platinum resistance) Pt100, Pt1000 and (C copper resistance) Cu50, Cu100.
The measurement range of Pt100 thermal resistance is -200~850℃, the minimum range is 50℃, the absolute error is ±0.2℃, and the basic error is ±0.1%. The measurement range of platinum resistor model Pt1000 is only -200~250℃, and other parameters are exactly the same as Pt100.
The measurement range of Cu50 and Cu100 is -50~150℃, the minimum range is 50℃, the absolute error is ±0.4℃, and the basic error is ±0.1%.
Let’s talk about PT100 thermal resistor.
Pt100 is just a collection and detection component. It must be equipped with an auxiliary 5V~24ⅤDC single power supply when working. It uses the Wheatstone bridge principle to send electrical signals that change with linear rules into an integrated op amp block or an isolation transmitter. , to a single chip for processing to truly reflect the temperature value of the measured object. The thermostat issues corresponding instructions to control the temperature of the controlled object.
Commonly used PT100 thermal resistors are divided into two-wire, three-wire and four-wire systems. Judging from its graduation table, its measurement range is large, from minus -200℃ to +600℃.
The so-called PT100 actually means that its resistance value at standard 0℃ is 100Ω (ohms). And when the temperature goes below zero, its resistance value gradually decreases. The resistance value at -200℃ is approximately 18.5Ω. When the temperature rises from 0°C, its resistance increases. For example, when the temperature rises by 50°C, its resistance value is approximately 119Ω (ohms). Its resistance value is approximately 138Ω (ohms) at 100℃. Its resistance value is about 176Ω (ohm) at 200℃, and its resistance value is about 313Ω (ohm) at 600℃.
As mentioned above, the Cu50 thermal resistor can be derived. Its 50Ω refers to its resistance value at 0°C. When it is at -50℃, its resistance value will decrease from 50Ω to 39.2Ω. When it rises from 0℃ to 50℃, its resistance value will increase to 60.7Ω, and so on, when it reaches 150℃, its resistance value will rise to 82.13Ω.
It can be seen from the above that both PT100 thermal resistor and Cu50 thermal resistor have a large dynamic range and linearly changing resistance rules. They are paired with many types of temperature controllers to achieve temperature acquisition and control, and the effect is good. Therefore, it is widely used in high-precision temperature equipment such as medical treatment, motor manufacturing, cold storage, industrial control, temperature calculation, bridge resistance calculation, etc., with a wide range of applications.
