Power supply 24V - the basis of power supply of measuring systems

At the heart of the electrical supply of any modern measuring system is a 24V power supply. Without the participation of this element, it is impossible to imagine the work of any current loop. The principle of its work is the following: all electronic devices are assembled sequentially into one large ring, through which current flows (most often this is 4-20 mA). The 24V power supply is a voltage source. The magnitude of the current changes the sensor depending on the parameter. And as the receiver is the analog input Industrial controller. From the above it can be seen that the functioning of the remaining components of the system depends on its qualitative and reliable operation.

Circuit Implementation

The structure of any such device includes the following modules:

• Fuse insert.
• A step-down transformer.
• Diode bridge.
• Filter.
• Control block.

The fuse link is a fuse that protects the device from overload. Once a high current value is applied to the input, it burns out, resulting in the whole system being de-energized. At the same time, all its components remain functional. The transformer consists of two windings. The first of them is the primary one (220V is supplied to it), and the second one is secondary, on which 24V is obtained. That is, it just just lowers the tension. The diode bridge from the alternating signal makes a constant. The filter stabilizes all output parameters by smoothing various pulsations. The last component - the control unit - can be found only in modern devices such as a 24V power supply. It measures Output signals. If they go beyond the permissible limits, they de-energize the current loop. In this case, such a situation persists until their value returns to normal.

Specifications

• Maximum output current.
• Power supply.
• Number of output channels.
• Degree of protection of the housing.
• Type of fastening.
• Operating temperature range.

The first two parameters are interrelated. For example, if the output allows a maximum current of 22 mA, then the power of the unit will be 5.28 W (22 mA multiplied by 24 V, current per voltage). To minimize the space occupied by such devices in the measuring cabinets, multi-channel sources are used. This is justifiable in cases where a number of measurement parameters are present in the system. The degree of protection of the case is indicated by the letters "IP" and the digital index. The bigger it is, the more securely everything inside is protected. This value should be paid attention in those cases when it is necessary to operate in an aggressive environment (for example, in the chemical or metallurgical industry). According to the type of attachment, such devices can be of two types: screwed and DIN rail. The first of these is outdated modifications, which gradually disappear from everyday life. The latter are installed on a special rail, and this has become the de facto standard to date. The last parameter that characterizes the power supply 24V is the operating temperature range. It should be paid attention only if it is planned to operate in some extreme conditions (for example, when the value of this parameter can drop to minus 40-50 degrees Celsius).

How to choose?

The algorithm for selecting such devices is as follows. Determine the number of consumers and their total capacity. Let's assume, work with a powerful electromagnetic valve on 100Вт and a current at a mode of peak loading in 5А is supposed. It is recommended to take a margin of about 20%. To do this, we multiply 100W by 1.2, we get 120W - power, indicating that our power supply 24V 5A (120W / 24V) will have exactly these indicators. It is from the devices with such characteristics and you need to choose. Further, it is necessary to take into account the operating conditions and the temperature regime, if necessary.

Let's sum up the results

The 24V power supply units are very important components of modern process control systems. Without them, it is impossible to imagine the full operation of any measuring system to date. Their choice must be approached very thoroughly. In the event of a failure of such a component, other parts of the system may fail.