Unified analog signals in automation systems. News and analytical portal "electronics time" Why a modulated burner is better than a single-stage one
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Shipment:
- consolidated cargo PEK 2 times a week, free of charge to the terminal in St. Petersburg;
- courier delivery EMS, 4S daily (very profitable for Moscow);
- Russian Post (for only 350 rubles to anywhere in the country) daily
Delivery: from 24 hours. Depends on the region and method of transportation.
Payment: or cashless payment.
Guarantee: 12 months
Air valve drive 0-10V control.
Technical specifications briefly
This drive is a general purpose drive.
Application area:
Control of the air damper of the supply or exhaust duct of the air duct.
A drive with a 0-10V control signal is convenient to use with, which is capable of generating a 0-10V signal
on one's own. This ensures fully automatic control of the opening and closing of the damper, depending on the temperature.
This type of drive
cannot be used with fire and smoke dampers.
Complete technical data for the drive
Electrical data |
Rated voltage | AC220V 50-60Hz |
| permissible voltage | AC 230V | |
| power consumption |
3W when rotating 0.5W on hold |
|
| wire cross section | 0.5mm2 | |
| Functional |
torque | 2N*m |
| valve size | up to 0.5m2 | |
| direction of rotation | Left right | |
| manual redirection | not provided | |
| rotation angle | Max. 90 degrees, limited by mechanical stop | |
| opening time | <30 сек. (90град) | |
| noise level | 45dB | |
| position indication | mechanical | |
| Working conditions |
protection class | 3rd (safety of low-voltage equipment) |
| protection level | IP54 | |
| working temperature | -20..+50 degrees Celsius \ IEC721-3-3 | |
| storage temperature | -30..+80 degrees Celsius \ IEC721-3-2 |
Dimensional characteristics of the air valve actuator
When automating technological processes, various sensors and actuators are used. Both of them are in one way or another connected to controllers or input/output modules, which receive measured values of physical parameters from sensors and control actuators.
Imagine that all devices connected to the controller had different interfaces - then manufacturers would have to produce a huge number of input/output modules, and in order to replace, for example, a faulty sensor, they would have to look for exactly the same one.
That is why, in industrial automation systems, it is customary to unify the interfaces of various devices.
In this article we will talk about unified analog signals. Go!
Unified Analog Signals
We deal with analog signals when measuring any physical quantities (temperature, humidity, pressure, etc.), as well as during continuous control of actuators (motor speed control using a frequency converter; temperature control using a heater, etc.). d.).
In all of the above and similar cases, analog (continuous) signals are used.
In controller equipment, in the vast majority of cases, two types of analog signals are used: a current 4-20 mA and a voltage signal 0-10 V.
Unified voltage signal 0-10 V
When using this type of signal to obtain information from a sensor, its entire (sensor) range is divided into a voltage range of 0-10 V. For example, a temperature sensor has ranges of -10...+70 °C. Then at -10 °C the sensor output will be 0 V, and at +70 °C - 10 V. All intermediate values are found from proportion.
The same is true for any other device. For example, if the analog output of a frequency converter is configured to transmit the current engine rotation speed, then 0 V at its output means that the engine is stopped, and 10 V means that the engine is spinning at maximum frequency.
0-10V signal control
Using a unified voltage signal, you can not only obtain data on physical quantities, but also control devices. For example, you can bring it to the desired position, change the rotation speed of the electric motor through a frequency converter or the power of the heater.
Let’s take, for example, an electric motor whose rotational speed is controlled by a frequency converter.
The engine rotation speed is set by the controller with a 0-10 V signal arriving at the analog input of the frequency converter. The engine rotation frequency can be from 0 to 50 Hz. Then, if, in accordance with the algorithm, the controller is going to spin the motor at 25 Hz, it must supply 5V to the input of the frequency converter.
"Current loop": unified analog signal 4-20 mA
The 4-20 mA analog signal (also called the “current loop”), as well as the 0-10 V voltage signal, is used in automation to receive information from sensors and control various devices.
Compared to the 0-10 V signal, the 4-20 mA signal has several advantages:
- First, the current signal can be transmitted over longer distances compared to a 0-10V signal, which experiences a voltage drop over a long line due to the resistance of the conductors.
- Secondly, it is easy to diagnose a broken line, because the operating range of the signal starts from 4 mA. Therefore, if the input is 0 mA, it means there is a break in the line.
4-20 mA signal control
Controlling various devices using a current signal is no different from controlling them using a voltage signal. Only in this case, you need a source not of voltage, but of current.
If a device has a 4-20 mA control input, then such a device can be controlled by a controller or other intelligent device that has an appropriate output.
For example, we want to smoothly open a valve that has an electric drive with a 4-20 mA input. If you apply a current signal of 4 mA to the input, then the valve will be completely closed, and if you apply 20 mA, it will be completely open.
Active and passive analog output 4-20 mA
Often, the analog output of a sensor, controller or other device is passive, that is, it cannot be a source of current without external power. Therefore, when designing an automation circuit, you need to carefully study the characteristics of the analog outputs of the devices used, and if they are passive, add an external power source to the circuit to impregnate the current loop.
The figure shows a diagram of connecting a sensor with a 4-20 mA output to a meter-regulator with a corresponding input. Since the sensor output is passive, it requires impregnation with an external power supply.
When measuring a physical quantity (temperature, humidity, gas contamination, pH, etc.), sensors convert its value into current, voltage, resistance, capacitance, etc. (depending on the operating principle of the sensor). In order to bring the sensor output signal to a unified signal, normalizing converters are used.
Normalizing converter is a device that converts the signal of the primary converter to a unified current or voltage signal.
This is what a temperature sensor with a normalizing converter looks like:
Dimmer - in Russian - a dimmer, which is used to adjust the brightness of luminaires in a lighting system.
When designing audiovisual complexes (AVC) of premises, sometimes the task arises of controlling the lighting system in a given room using an integrated AVC control system.
Additional requirements are imposed on the lighting system of premises equipped with emergency lighting systems: lighting zoning (dividing lamps into groups according to functional purpose); possibility of smooth adjustment of illumination (dimming) in individual zones.
The choice of the type of dimmers and dimmer control interfaces is complicated by the fact that often, at the design stage, it is not possible to obtain detailed technical information from the customer about the lighting system luminaires used. But there are no universal dimmers for controlling any type of lamps; some types of lamps are not dimmable at all!
To minimize compatibility risks, the best option for the AVK designer is when the luminaire supplier supplies the luminaires complete with appropriate dimmers (usually electronic ballasts with an additional dimming option). All that remains is to determine the control interface for such dimmers.
Electronic Start-Regulating Apparatus (EPG, electronic ballast) is an electronic device that ensures the start-up and maintenance of the operating mode of gas-discharge lighting lamps.
You can debate for a long time about the choice of interface type, but the simplest from the point of view of connection and configuration, as well as the cheaper one, is the 0-10 V analog interface.
Analog interface 0-10 V.
This analog interface is defined in IEC 60929 (Annex E). The interface uses one control wire, through which the control signal 0 - 10 V (plus the neutral wire) is transmitted. The control device can be a special dimmer or circuit as part of the control system. The control device or dimmer works as a current source, which allows you to control several electronic ballasts connected in parallel. The control voltage value of 10 V provides maximum brightness of the lamp, which linearly decreases to zero when the voltage decreases to 0 V, as shown in the figure.
A voltage of 10 V corresponds to maximum brightness (100%), and 0 V corresponds to turning off the light (0%) or the lowest possible brightness level.
So, we connect lamps with a dimmer (dimmable electronic ballasts) via a 0-10 V interface to the control controller. We control the light: reduce the intensity, increase it, everything works great. We want to turn off the lamp by reducing the control voltage to 0 V, but we cannot, the lamps continue to burn with a low brightness level. What's the matter - it's a hitch. We look carefully at the documentation and see that the operating control voltage of the electronic ballast is 1-10 V! It is impossible to turn off such a lamp by reducing the control voltage to 0 V. Unfortunately, sometimes this becomes clear at the very last moment, when the equipment has already been purchased and installed.
If you plan to use luminaires with a dimmer (dimmable electronic ballasts) connected via a 0-10 V interface, it is necessary to provide for the installation of an additional relay for each group of luminaires.
