How to use a multimeter to convert an RTD signal into a rough temperature reading
Commonly used pointer multimeters and digital multimeters can roughly estimate the approximate temperature range of RTDs.
Commonly used RTDs are (Pt resistance) Pt100, Pt1000 and (C copper resistance) Cu50, Cu100.
The measurement range of Pt100 RTD is from -200 to 850°C, with a minimum range of 50°C, an absolute error of ±0.2°C, and a basic error of ±0.1 per cent. And Pt1000 this type of platinum resistance its measurement range is only -200 ~ 250 ℃, other parameters and Pt100 exactly the same.
Cu50 and Cu100 measurement range are -50 ~ 150 ℃, the minimum range of 50 ℃, the absolute error of ± 0.4 ℃, the basic error of ± 0.1%.
The following on the PT100 RTD to say a few words.
Pt100 it is just a collection of detection components, it must be equipped with auxiliary 5V ~ 24 Ⅴ DC DC single power supply, the use of Whisden bridge principle, with the linear law of changes in electrical signals into the integrated operational amplifier block, or isolation of the transmitter, to the monolithic chip for processing, to truly reflect the temperature value of the object being measured. By the thermostat issued by the corresponding instructions to control the temperature of the controlled object.
Commonly used PT100 RTD, divided into two-wire, three-wire, four-wire system. From its indexing table, it has a large measuring range, which can be from -200℃ to +600℃ below zero.
The so-called PT100 actually means that it has a resistance value of 100 Ω (ohm) at the standard 0℃. And it shows a gradual decrease in its resistance value as the temperature goes below zero. In -200 ℃ when the resistance value of about 18.5 Ω. And it is in the temperature from 0 ℃ when rising, its resistance value is to run to the big. For example, when the temperature rises 50 ° C, its resistance value of about 119 Ω (ohms), 100 ° C when its resistance value of about 138 Ω (ohms), 200 ° C when its resistance value of about 176 Ω (ohms), 600 ° C when its resistance value of about 313 Ω (ohms).
As the above can be introduced Cu50 RTD, it 50Ω refers to its resistance value at 0 ℃. When it is -50 ℃, its resistance value will be reduced from 50 Ω to 39.2 Ω. When it rises from 0 ℃ to 50 ℃, its resistance value will increase to 60.7 Ω, so analogous, to 150 ℃, its resistance value will rise to 82.13 Ω.
From the above, it can be seen that both PT100 RTD and Cu50 RTD have a large dynamic range and linear change of resistance law, it is assigned to many types of temperature controllers to achieve temperature acquisition and control, the effect is good. Therefore, it is widely used in medical, motor manufacturing, cold storage, industrial industrial control, temperature calculation, bridge resistance calculation and other high-precision temperature equipment, the application range is very wide.
In order to facilitate the use of multimeter to, check the Pt100 and Cu50 this commonly used two kinds of RTD, the following lists the production of these two kinds of RTD index table, for you to test against the use of.
