Why is the oscilloscope waveform jagged after it is enlarged?

First, the introduction

Pt100, that is to say its resistance is 100 ohms at 0 degrees, PT100 temperature It is a resistive temperature sensor made of platinum (Pt), which belongs to the positive resistivity. The relationship between resistance and temperature change is as follows: R=Ro(1+αT).

Second, the main technical parameters of the Pt100 temperature sensor are as follows

1. Measurement range: -200°C～+850°C; allowable deviation value △°C: Class A±(0.15+0.002│t│), Class B±(0.30+0.005│t│); Thermal response time current≤ 5mA. In addition, Pt100 temperature sensor also has the advantages of anti-vibration, good stability, high accuracy and high pressure resistance.

Third, the connection of three core wires of PT100 temperature sensor

1. PT100 platinum resistance sensor has three leads. A, B, C (or black, red, yellow) can be used to represent three wires. The following rules exist between the three wires: the resistance between A and B or C is at room temperature. About 110 ohms, between 0 and C is 0 ohms, B and C are straight inside, in principle, B and C are no different.

2. There are three fixed terminals for the sensor connected to the meter:

The A line is connected to a fixed terminal of the sensor on the meter. The two terminals are connected to the other two fixed terminals on the meter. The positions of the B and C lines can be interchanged, but they must be connected. If there is an indirect extension in the middle, the specifications and length of the three conductors are the same. The 3-wire and 4-wire connection of the thermal resistor: 2-wire, 3-wire, and 4-wire are used, which are mainly determined by the secondary instrument used for (selection). Generally, the display instrument provides a three-wire connection. One end of the PT100 has one line, and the other end has two lines. Both are connected to the meter, and the inside of the meter is used to offset the resistance of the wire through the bridge. The general PLC is four wires, two wires are output at each end, two are connected to the PLC output constant current source, and the PLC measures the voltage on the PT100 through the other two. It is also used to offset the wire resistance. The four wires have the highest accuracy, and the three wires can also be used. The line is the lowest, the specific usage should consider the accuracy requirements and costs.

Fourth, PT100 temperature sensor product features

1, stainless steel sleeve package, durable

2, the movable screw is fixed, easy to use

3. Manufactured in accordance with international IEC751 international standards, plug and play

4, a variety of probe sizes are available, adapt to a wide range

5, high precision, high stability, high sensitivity

6, small size, economical and practical

7, characteristic indicators

● Temperature range: -200-400 °C

●Probe length: 5cm/10cm/15cm/20cm

● Probe diameter: Φ5mm

●Resistance change: 0.3851Ω/°C

●Installation method: movable screw fixing

● Screw specifications: M8*1.0

● Lead length: generally 2 meters, can be customized length (dedicated lead)

●Lead connection method: three-wire type

● Wiring method: wiring fork

●Sleeve material: stainless steel

●Sensor device: PT (platinum)

Fifth, the reason why the PT100 temperature sensor adopts the three-wire connection method:

The resistance value of the PT100 temperature sensor at 0 °C is 100 Ω, and the resistance change rate is 0.3851 Ω/°C. Because of its small resistance value and high sensitivity, the resistance of the lead wire can not be neglected. The three-wire connection method can eliminate the measurement error caused by the lead line resistance. The principle is as follows:

The cross-sectional area and length of the three wires drawn by PT100 are the same (ie r1=r2=r3). The circuit for measuring platinum resistance is generally an unbalanced bridge. The platinum resistance (Rpt100) is used as a bridge arm resistance of the bridge. (r1) Connected to the power supply end of the bridge, the other two (r2, r3) are respectively connected to the bridge arm where the platinum resistance is located and the adjacent bridge arm, so that the two bridge arms are introduced with the same resistance of the lead resistance. The bridge is in equilibrium and the change in lead resistance has no effect on the measurement results.

Wiring diagram:

Dimensions:

Selection chart:

Five, PT100 principle and index table

Resistive Temperature Detector (RTD) - A resistance made of a material that changes its resistance as temperature rises. If it rises with temperature, the resistance increases as a positive resistivity. If it rises with temperature and the resistance value decreases, it is called negative resistance coefficient. Most resistive temperature sensors are made of metal. Among them, resistive temperature detectors made of platinum (Pt) are the most stable - acid and alkali resistant, non-deteriorating, and quite linear.

The PT100 temperature sensor is a resistive temperature sensor made of platinum (Pt). It belongs to the positive resistivity. The relationship between resistance and temperature change is as follows: R=Ro(1+αT) where α=0.00392 and Ro is 100Ω ( In the resistance value of 0 ° C), T is Celsius temperature, so the resistive temperature sensor made of platinum, also known as PT100

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