How does a mechanical water meter work?
Working principle of mechanical water meter
The water meter on the water pipe has several small pointers arranged along an arc on the dial of the water meter. There is a small red triangle in the center. When the water is flowing, the small red triangle will rotate. As for the small hands, they almost didn't move even if the water didn't flow.
The words "m3" are also written on the dial, which means cubic meters. That is to say, the unit of the reading of this meter is cubic meters. Because every cubic meter of water weighs exactly one ton, the reading is directly the number of tons, so the water fee can be easily calculated based on the reading (tons) of the total amount of water used.
So what is the working principle of the water meter?
It's actually very simple, because the housing of the water meter is fixed, its internal volume is fixed, and the water is flowing, it pushes an impeller to rotate, and whenever the impeller rotates a circle, a constant volume of water flows through. Therefore, as long as the number of revolutions of the impeller is accumulated and multiplied by this constant volume, the total amount of water flowing through can be obtained.
We have already understood the principle, so let's take a look at the inside of the water meter in detail, because in order to prevent users from cheating, there is a lead seal on the lid and it is not allowed to open it.
The internal structure of the water meter can be divided into three parts: the shell, the sleeve and the inner core from the outside to the inside. The shell is made of cast iron, and the water passes through the lower annular space of the shell after coming out of the water inlet, which is called the "lower ring chamber" here. Above this annular space there is an "upper annular chamber" communicating with the water outlet. There is a filter with small holes at the bottom of the sleeve to filter out debris in the water. There are two rows of upper and lower round holes on the side of the sleeve, and the positions of the holes are exactly opposite to the upper and lower ring chambers of the shell. Obviously, the lower row is the water inlet and the upper row is the water outlet. It is particularly worth noting that these two rows of holes are punched diagonally along the tangent direction of the circle, and its work is shown in the animation. Note that the directions of the upper and lower rows of holes are opposite. The water flows in the tangential direction from the lower row of holes, and it is bound to form a rotating water flow, which is very important for the work of the water meter.
Let's take a look at the inner core again. The inner core is divided into upper, middle and lower layers. What we see from the glass window is the upper layer, with only the pointer and the dial. In fact, the key is the lower layer. There is a plastic wheel inside, and there are many plastic blades on the side of the wheel, which are called "impellers".
The position of the impeller is exactly in the rotating flow formed by the lower hole of the casing. The water flow impacts the blades around the wheel, generating torque, and rotating the impeller. The greater the opening, the faster the water flow, and the faster the impeller will turn.
The shaft of the impeller reaches the middle layer vertically upwards, and there is a pinion on the shaft, which meshes with the "decimal number gear" to achieve the purpose of accumulating the number of revolutions. The function of the "decimal number gear" is that whenever the single digit gear rotates ten times, the tens digit gear rotates once. In other words, if the single-digit gear rotates once, the tens-digit gear rotates one-tenth of a turn. The single-digit gear is the active one, which drives the tens-digit gear. In fact, each level of decimal is completed with two pairs of gears to make the direction of rotation consistent. One pair of gears is 9:30 and the other is 10:30. These two pairs are connected in series, and the total gear ratio is this. The product of the two, 0.099999, can be approximately 0.1.
According to this calculation, if you want to read seven digits (four digits before the decimal point is a black scale, and three digits after the decimal point are a red scale), you have to use 12 pairs of gears. In addition to other uses, 18 shafts and 34 gears are squeezed into this small space in the middle, which can be regarded as high-density installation.
Although we are now in the 21st century, this mechanical water meter can still serve us for a long time because of its simplicity and low price, and can be used in a humid environment for a long time without maintenance, and does not require a power source, and the advantages of power failure will not affect the work. Of course, the current electronic technology tap water meter is also deeply loved by major users. If you want to know more, please feel free to consult us.