The main component of a bimetallic thermometer is a multi-layer metal sheet composed of two or more metal sheets stacked together, which works based on the principle that two different metals expand differently when the temperature changes. It is composed of bimetallic sheets wound into a circular curved shape. When one end expands due to heat, it drives the pointer to rotate, and the working instrument displays the temperature value corresponding to the thermoelectric potential.

2、 Working principle of bimetallic thermometer

The working principle of a bimetallic thermometer is to use two metals with different temperature expansion coefficients to improve temperature measurement accuracy

Sensitivity is usually achieved by making metal sheets into a spiral coil shape. When the temperature of multiple layers of metal sheets changes, the expansion or contraction of each layer of metal is uneven, causing the spiral coil to roll up or loosen.

Due to one end of the spiral coil being fixed and the other end being connected to a freely rotatable pointer, when the bimetallic strip senses a temperature change, the pointer can indicate the temperature on a circular scale.

The temperature measurement range of this instrument is 200~650 ℃, and the allowable error is about 1% of the scale's two strokes.

3、 Classification and selection instructions for bimetallic thermometers

1. Classification

Bimetallic thermometers can be classified into four types based on the direction of connection between the pointer plate and the protective tube: axial type, radial type, 135 ° directional type, and universal type.

① Axial bimetallic thermometer: The pointer plate is vertically connected to the protective tube.

② Radial bimetallic thermometer: The pointer plate is connected parallel to the protective tube.

③ 135 ° directional bimetallic thermometer: The pointer plate is connected to the protective tube at a 135 ° angle.

④ Universal bimetallic thermometer: The connection angle between the pointer plate and the protective tube can be adjusted arbitrarily.

2. Installation fixed form

In order to meet the needs of actual production, bimetallic thermometers have different installation and fixing forms: movable external threaded pipe joints, movable internal threaded pipe joints, fixed threaded joints, sleeve threaded joints, sleeve flange joints, and fixed flanges.

3. Model naming convention

W S S □□□□ - Protection form

No - ordinary type

Installation and fixing method W-protective type

0-No fixed device F-Anti corrosion type

Structural form 1- movable external thread

0-axial type 2-movable internal thread

1- Radial type 3- Fixed thread

2-135 ° Type 4 Fixed Thread

3-universal type 5-card sleeve thread

Case nominal diameter 6-card sleeve flange

3- φ 60

4- φ 100

5- φ 125

The temperature sensing element is bimetallic

Metal expansion type