What are the structural characteristics of thermal resistors? Common troubleshooting methods

What are the structural characteristics of thermoelectric resistors? Resistance is the most commonly used temperature detector in the medium to low temperature region, and its main characteristics are high detection accuracy and stable quality. Platinum thermistors have the highest measurement accuracy and are not only widely used in industrial temperature measurement, but also made into standard instruments. The temperature measurement principle of thermoelectric resistance is to measure temperature and temperature related parameter values based on the variation of the resistance value of a conductor or semiconductor with temperature. Thermal resistance belongs to the conventional measurement surface and requires a large amount of on-site usage and maintenance. What are the structural characteristics of thermal resistance? If you are interested in the content that will be covered in this article, why not continue reading.

The structural characteristics of thermal resistance:

Thermal resistance is generally used in conjunction with digital instruments, recording instruments, and electronic regulators. It can directly measure the temperature of liquid, steam, gas medium, and solid surface in various production processes from -200 ℃ to 600 ℃ within the range.

(1) WZ thermal resistance series installation: generally composed of temperature sensing components, installation positioning devices, junction boxes and other main components, with high detection accuracy, safety and reliability characteristics. The specific application program is Pt100 platinum thermistor, which is the most widely used.

(2) WZPK series armored platinum thermistor: Armored thermistor is a sturdy body composed of temperature sensing elements, wires, insulation materials, and stainless steel sleeves. It has the advantages of slender body shape, fast thermal response time, vibration resistance, and strong durability.

(3) Explosion-proof thermal resistance: Based on the special structure of the junction box, the explosion-proof thermal resistance limits the explosion caused by flames or electric arcs in the explosive mixture inside the junction box to the junction box, and will not cause explosion at the work site.

(4) End face thermal resistance: The temperature sensing element of the end face thermal resistance is wrapped with specially treated electric heating wires, close to the end face of the thermometer. Compared with general radial thermal resistance, it can more accurately and faster reflect the specific temperature of the end face to be measured, and is suitable for measuring the appearance temperature.

Thermal resistance characteristics:

(1) Platinum thermistor: Platinum exhibits stable physical and chemical properties, high detection accuracy, and stable quality in reducing media, even at high temperatures. Above 0 ℃, the relationship between resistance and humidity is close to a straight line. However, the resistance temperature coefficient of platinum is relatively small, and it is prone to embrittlement in oxides, changing its resistance temperature characteristics. Original resistance R0=100 euros

(2) Copper thermal resistance: -50 ℃ - The correlation between copper resistance and humidity is basically linear at an ambient temperature of 180 ℃. But the resistance is low, the volume of the resistor body is large, the thermal inertia is large, and oxidation is obvious above 100 ℃.

Common thermal resistance problems and solutions

(1) The displayed value of the display instrument is lower than the actual value or the range is unstable

The possible cause is water storage in the pipeline or metal shavings, dust, etc. in the junction box.

Treatment method: Pour water or eliminate dust, dry the wet and cold parts, improve insulation performance, but do not burn.

(2) Indicates infinite value

Short circuit of thermal resistance or leads, loose wiring terminals, etc.

Processing method: Replace the resistor body, or weld and lemon wiring screws

(3) Changes in resistance values related to temperature

Platinum resistance wire material corroded and deteriorated

Handling method: Replace the thermoelectric heating wire:

(4) The displayed value of the instrument is zero or has a negative number

Digital display and thermal resistor wiring error, or thermal resistor short circuit

Solution: Correct wiring or find short circuits, strengthen insulation

(5) Thermal resistance short circuit

Use a multimeter to check the location of the short circuit and determine whether it is a connecting wire or a thermal resistor short circuit. If the connecting wire is short circuited, it should be repaired or replaced.

(6) Thermal resistance short circuit

If the thermal resistor itself is short circuited, it should be replaced. Check with a multimeter to determine the location of the short circuit and repair or replace it.

In addition, after installation, the thermal resistor cover in a damp environment should be regularly opened to prevent rusting and prevent inability to open and maintain. Based on the relationship between the temperature and resistance value of PT100, we should have a corresponding approximate calculation formula for 100 euros, O degrees, with each ohm increasing by approximately 2.4 degrees (for example, a temperature of approximately 24 degrees measured at 110 euros, and then measured with a multimeter to determine whether it is the thermal resistance itself).

Some thermoelectric resistors are exposed to high temperatures all year round, and when connected with copper wire, an oxide layer may appear, which affects the measurement value. They can be restored by scraping them off with sandpaper or pliers before being connected.

Maintenance precautions are as follows:

(1) Using a multimeter R × Check the resistance value at first gear, and if the multimeter is marked with "∞ thermal resistance short circuit, it cannot be used.

(2) The thermal resistor should be moisture-proof, otherwise it may cause a short circuit in the thermal resistor.

(3) Strictly follow the periodic verification plan for measuring instruments and submit them for inspection. Only after passing the verification can they be used.

(4) When using, tighten the street screws of the leads and the thermal resistor patch panel.

(5) Carefully inspect the casing welds and threads for leaks.

(6) Carefully check the integrity of the protective cover, plug, and gland seals.

(7) After removing the thermal resistance temperature sensing element from the protective tube, the rust or oil stains inside the maintenance tube should be removed;

(8) Platinum resistors should not be touched by hand with platinum wires, nor should they be removed; The copper resistor shall not be removed from the frame with the wire wrapped;

(9) When adjusting the resistance R0 at temperature 0, the R0 value should be adjusted at the tail end. If R0 is too small, the copper resistance can be increased by welding wire with the same diameter; Platinum resistors can be slightly elongated with tools to increase;

(10) When installing the temperature sensing element in the protective tube, if the wire is found to be too short, the copper wire can be connected to a copper resistor of the same diameter; Platinum resistors can connect silver wires of the same diameter.

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Service hotline: 134-3440-1267, 155-2178-1275? Common troubleshooting methods