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Pressure gauge common problems and maintenance methods

Author:QINSUN Released in:2023-04 Click:24

First, the error of the tested gauge always increases or Decrease a fixed value

The characteristic of this error is that the error of the meter under test increases or decreases at the same rate as the pressure increases. Throughout the measuring range, the pointer reading is always consistent with the default indicator value. The difference is a fixed value, which is a system error caused by incorrect pointer installation. It is very easy to adjust this error, as long as the needle is re-adjusted to the installation position of the pointer, it can be eliminated. If the error is minor, turning the knob slightly can solve the problem.

Second, the error of the tested gauge increases or decreases proportionally

There is basically no major problem with the pressure gauge with this error, mainly caused by the changeg of the gear ratio, just move The indication value adjusting screw can be solved. When the error of the tested gauge gradually increases, move the indicator adjustment screw to the right (down), increase the arm length of the short arm of the sector gear and decrease the gear ratio. When the error of the meter under test gradually decreases, the adjusting screw of the indicator should be moved to the left (up), the arm length of the short arm of the sector gear should be reduced, and the gear ratio should be increased.

Thirdly, the speed of the meter under test indications is different

The so-called \"different speed\" refers to the error obtained in calibration, which does not increase or decrease proportionally with the increase in pressure. Instead, it gradually tends to a negative value from a positive value or gradually tends to a positive value from a negationve value, so it is also called as a nonlinear error or a curve error. At this time, it is necessary to change the angle between the connecting rod and the fan-shaped teeth. The nonlinear error can be adjusted, and the angle between the connecting rod and the fan-shaped teeth can be adjusted smaller. The pointer moves faster in the first half of the scale, and the pointer moves more slowly in the second half of the scale. ; Adjust the angle between the connecting rod and the fan-shaped teeth, the pointer will move slowly in the first half of the scale, and the pointer will move faster in the second half of the scale. In another case, when the watch is turned clockwise, the hands in the first half of the scale move slowly, while the hands in the second half of the scale move quickly. .

Fourth, the pointer does not return to zero or is less than full.

1. The coil spring is not tight or stretched enough, and some are notet stiff enough due to term use When the hairspring is close to zero Insufficient flexibility at bit or full scale, loss of ability to control the pointer.

2. The fixed position of the movement is not suitable, the angle between the connecting rod and the fan-shaped teeth is too small, the position of the movement needs to be changed or the number of meshing teeth should be increased .

3. The connecting rod is too short, the magnification angle of the transmission mechanism is limited, and the pointer cannot reach the full scale and zero position.

4. If the gear ratio is too small and the pointer cannot reach the full scale, the length of the short arm of the fan-shaped tooth should be reduced to speed up the indication value.

5. After repeated adjustments, the indication value still changes disproportionately, it should be judged that the spring tube is deformed and cannot be repaired, and a new one should bewill be replaced.

5. Stuck needle or skipped needle

1. The teeth are rusted, worn, or have burrs and debris between the teeth.

2. The shaft hole is worn, the shaft collides with the wall of the hole on one side during rotation, or the connecting rod is wedged with the connecting piece by friction at some point.

6. Tap Displacement

The pointer should rotate counterclockwise in normal state after tapping the body, otherwise there should be a tap displacement. In addition to tapping the position to remove the coil spring, in many cases this is caused by friction between parts. Poor assembly has caused parts to be installed loosely or too tightly. Displacement due to tapping is often due to the following reasons:

1. The coil spring is not coiled tightly or stretched enough, or the two ends of the coil spring may not be properly tightened.

2. There is friction between the transmission parts,which affects the drag of the free end of the spring tube to the transmission reinforcement mechanism and pointer assembly. It is common that the connecting rod is not flexible, the transmission shaft is crushed to death, or the shaft and hole are too fit waiting.

3. A loose screw somewhere, especially the looseness of the adjustment screw of the indicator has the greatest impact.

4. Teeth grip poorly, there are slippery or obstructive phenomena.

5. The pointer is loose, or the pointer sleeve and pointer piece are loose.

7. Installation And Disassembly Of The Spiral Spring Of The Pressure Gauge

1. The Function Of The Spiral Spring

Use The Spiral Spring To Generate Reaction Torque, So The Gear Holds The One-way Position Profile Firmly Contact, To The to eliminate unstable condition of the indication caused by the meshing gap between gear and sector gear, the gap between the transmissionie shaft and the connecting rod, etc., so that the pointer is installed smoothly, and the value of the watch case remains unchanged when tapped. That is, when the pressure is removed, the auxiliary pointer returns to the zero position and is close to the stop rivet.

2. Characteristics of coil spring

When the tension of the lower limit measured by the pressure gauge is sufficient and in the state of maximum torque, as the pressure increases, the torque gradually decreases, and the spiral spring is inverted, on the contrary. In the zero position, the coil spring is in a pre-tensioned state, and as the pressure increases, the coil spring gradually relaxes. When the coil spring is too long, the stiffness is weak, the elasticity is poor, the pointer is unstable, and even the free state seems to be stuck; while the coil spring is too short, the frame spacing is very different after being increased, and even one side is tied, and the force is uneven.

3. Technical requirements for coil spring

(1) There should be no significant eccentricity after installation and the plane should be perpendicular to the intermediate shaft.

(2) After loosening, tightening or opening, the circles should be free, the distance between the circles should be relatively uniform, and there should be no phenomenon of merging or overlapping circles.

(3) The core hole, diameter and torque must meet the installation specifications.

(4) After installation, both ends of the coil spring are tightened without releasing.

VII. Points to note after the verification work

1. Check that all screws are tightened. The tightening of the value adjusting screw is especially important, it should be noted that after the movement is screwed in, the notch at the top for turning should not be in a horizontal direction to avoid embedding the spiral spring.

2. Pressure gauges that failcome the verification, must be downgraded before use. Change accuracy class flags properly.

3. After the scale is installed, check that the dial shaft and pointer touch the glass, and lightly shake the watch case to hear if there is any noise, to avoid damaging parts or little things left behind.