To comply with the necessary safety conditions, it is important that the operating parameters of technological installations do not exceed emergency values. If such situations arise, the automatic control system must immediately stop the operation of the equipment and prevent it from starting until the problems are eliminated or until the required values of the technological parameters of the controlled environment are achieved.
Today there are a huge number of process control devices on the market. For example, one of the sensors for measuring and monitoring pressure is an electric contact pressure gauge.
Connection diagrams for electrical contact pressure gauges
Electrical contact pressure gauges have become very widespread in safety automation systems of boiler houses, combined heat and power plants and central heating stations.
They not only control pressure, but also perfectly allow for the control of production processes, in particular, turning pumps on and off. In these aspects, ECMs are an excellent alternative to pressure switches. For example, to ensure control of the pressure of a water heating boiler within acceptable limits, you need either two pressure switches (a separate low pressure switch and a separate high pressure switch), or just one electric contact pressure gauge with two contact groups. The following types of ECM are produced by industry:
- electric contact pressure gauges on microswitches;
- electrical contact pressure gauges with magnetomechanical contacts;
- explosion-proof.
To understand whether the use of an electrical contact pressure gauge in this particular circuit will be justified, you need to consider the advantages and disadvantages of this device.
When installing the ECM, no tees or fittings are required, since it is already assembled in a single housing for switching contacts and a control pressure gauge. That is, in one device we can not only control the pressure, but also see its current value. Also, the advantages of an electric contact pressure gauge are the ease of setting it up, as well as more accurate visualization of the configured pressure response limits. Limits are adjusted using contact arrows, without the use of specialized tools, only an indicator screwdriver is needed.
The disadvantage of ECM is low switching currents (only 300-500 mA), which requires connecting high-power controlled devices through intermediate relays to avoid burning out the pressure gauge contacts.
Schematic electrical diagrams of electrical contact pressure gauges
Types of electrical contact pressure gauges: 1 - index arrow; 2,3 - electrical contact settings; 4.5 - zones of closed and open contacts, respectively; 6.7 - objects of influence
Electrical contact pressure gauges have a typical operating diagram, which can be illustrated in the previous figure. When the pressure increases and it reaches a certain value, the index arrow 1 with an electrical contact enters zone 4 and closes the electrical circuit of the device using common contact 2, which in turn leads to the activation of the affected object 6.
Electric contact pressure gauge DM2010SgU2 version 5
Depending on the purpose, various modifications of the ECM are used, having the following designs of electrical circuits:
- Version 1 – with one short-circuit contact;
- Version 2 – with one open contact;
- Version 3 – with two open-open contacts;
- Version 4 – with two contacts for short circuit;
- Version 5 – with two open-close contacts (the left contact is a break contact, the right contact is a make contact);
- Version 6 – with two contacts for making and breaking (the left contact is normally closed, the right contact is normally closed).
Connecting an electrical contact pressure gauge
The most common ECM circuits in heating engineering are circuits with two contacts, that is, versions 3, 4, 5 and 6. Let's consider the connection using the example of an electrical contact pressure gauge DM2010SgU2.
In pressure gauges of this brand, the design can be determined by the color of the signal arrows:
- version 5 – both indicators are blue.
- version 6 – both indicators are red.
- version 3 – left indicator (min) – blue, right (max) – red;
- version 4 – left indicator (min) – red; right (max) – blue;
Electrical contact pressure gauges and operation of contact group versions
Electrical contact pressure gauges (ECM) are designed to automatically generate a signal and, in some cases, automatically regulate pressure or lock. Using an ECM, we can monitor pressure and see its current value. Limits are set using signal arrows (set points), without the use of specialized tools, only a screwdriver is needed.
According to the principle of operation, this device is similar to technical pressure gauges with the only difference being that special electrical contacts are added to it. The working arrow, with the help of a pin, leads a lever with a contact, which, in contact with a fixed contact on the set point, closes/opens the electrical circuit of the signaling or control device.
The ECM is configured to control the pressure in the working area (between the settings); the error in the readings beyond the settings may exceed the accuracy class of the pressure gauge. A screw-on permanent magnet is installed on the signal pointer, which gives the contact system a jumping characteristic and enhances the pressing of the contacts. When using an ECM with magnetic preload, it is necessary to remember the permissible operation error of 4%. Operation occurs with advance or delay relative to the movement of the arrow.
Filling the set point sector – the moving contact is closed with the contact on the set point.
The switching positions are indicated for the state when the arrow is between “0” and the nearest setpoint.
Red setpoint color
– closed in the work area.
Blue setpoint color
– open in the working area.
What kind of sensor is this and when is it used?
An electric contact pressure gauge is a sensor that is used to measure excess and vacuum pressure in various media (liquid, gas, steam), is used as a direct-acting signaling device and allows you to control production processes, while a special condition for the medium is to prevent its crystallization.
The ECM is used to issue control signals to actuators that maintain pressure values in the pipeline, as well as compressor units, hydraulic systems, pneumatic equipment or household autoclaves at a certain value.
The electrical contact pressure gauge is popular in many industries and infrastructure systems:
- Energy;
- Metallurgy;
- Oil and gas and petrochemical industry;
- Water supply systems;
- Mechanical engineering installations;
- Heat generation and distribution.
ECMs are also in demand in safety automation systems of thermal power plants, central heating stations and boiler houses.
Types of sensor models
There are many manufacturers involved in the production of electrical contact pressure gauges; some offer a fairly wide range of models; the list below is divided according to various manufacturing plants:
- TM (TV, TMV), 10th series;
- PGS23.100, PGS23.160;
- EKM100Vm, EKM160Vm;
- TM-510R.05, TM-510R.06, DM2005Sg and its analogue TM-610.05 ROSMA.
All of the listed models are divided into pressure gauges with microswitches and with magnetomechanical contacts. Manufacturers also produce devices that are explosion-proof and vibration-resistant or liquid-filled (filled inside with dielectric oil, most often glycerin) so that the readings of the pressure gauge needle do not “jump” with increased pulsation of the measured medium. Glycerin inside the ECM will prevent the needle from moving quickly.
Operating principle of electrical contact pressure gauges
The principle of operation of the ECM is that a moving contact closes or opens a certain set value. The movable contact of an electric contact pressure gauge is a pressure indicating arrow, which rotates when the pressure in the measured medium changes. The setpoint (adjustable) value is set manually using two arrows (minimum and maximum value). These pressure gauge needles are stationary after setting the values.
The value of the moving arrow in the working process, as a rule, is between two setpoints, but when it crosses the limit value, the contacts of the internal electrical circuit are closed or opened (depending on the type of model). These contacts can be used in various relay circuits to control, for example, pneumatic or solenoid valves, as well as magnetic starters of various motors.
Note! The switching capacity of the contacts of an electrical contact pressure gauge does not allow switching large load currents.
Each electrical contact pressure gauge has a marking that describes all its characteristics and type.
ECM device
The ECM is a cylinder-shaped device very similar to a conventional pressure gauge. But unlike it, the ECM includes two arrows that set the setpoint values: Pmax and Pmin (their movement is carried out manually along the dial scale). A moving arrow showing the real value of the measured pressure switches contact groups that close or open when it reaches the set value. All arrows are located on the same axis, but the places in which they are fixed are isolated and do not touch each other.
The axis of the indicator needle is isolated from the parts of the device, its body and scale. She rotates independently of others.
The bearings with which the arrows are attached are connected to special current-carrying plates (lamellas) connected to the corresponding arrow, and on the other side these plates are brought out into the contact group.
In addition to the above components, the ECM, like any pressure gauge, also has a sensitive element. In almost all models, this element is a Bourdon tube, which moves along with a pointer rigidly fixed to it; also, a multi-turn spring is used as this element for sensors that measure medium pressure more than 6 MPa.
Pressure gauge device
Among the advantages of this device, I would like to note that the pressure gauge itself and control and switching contacts are assembled in one housing, which means that during installation there will be no need to install extra fittings or tees. But the main positive quality of such devices is that it is very simple to set up and that with its help the pressure limits are more accurately visualized.
It looks like this: the operator, using arrows with contacts, sets pressure limits without using any special keys for this, and after setting it all will look very clearly (a quality that is completely absent from the relay).
Among the negative qualities of the device, I would like to note the small switching current (only 300-500 mA). In this regard, connecting high-power devices is only possible through powerful intermediate relays, which require their own power source to operate.
There are many options for circuits for connecting ECM pressure gauges, but I will show only one of the principles of constructing circuits and explain its operation. I will try to explain the principle of operation and the construction of circuit diagrams for switching on the device using the example of a device that controls the motor of a submersible pump.
This circuit, in addition to the ECM itself, contains a magnetic starter 1, a control relay 3, a time relay 6, a pair of intermediate relays 9 and 12 and an electric pump 18. It all works quite simply.
The phase wires of the supply network (A, B, C), through normally open contacts 2 of the starter 1, are connected to the supply contacts of the motor 18, which drives a submersible pump.
Since phases A and B of the supply network are also a power source for the starter coil 1, a chain is connected between them, consisting of a normally open contact 4 (3), a control relay and a starter coil
Connection diagrams for electrical contact pressure gauges
The figure shows typical possible ECM connection diagrams.
- 1 - main indicating arrow;
- 2 and 3—limit value settings;
- 4 and 5 - areas of closed and open contacts;
- 6 and 7 - external circuits in which the electrical contact pressure gauge is located.
Let's consider the operation of ECM contacts using the example of a sensor with version 1. When the pressure reaches the set value (2) by the working arrow (1), i.e. When the working arrow (1) enters zone 4, the ECM contact closes. When the pressure value drops below the setpoint arrow (2), the contact opens.
Which contact groups can be used depends on the type of device, and according to GOST 13717-84 Appendix 1 they exist in the following types:
- EXECUTION 1 - Normally open (NO), with one contact;
- EXECUTION 2 - Normally closed (NC), with one contact;
- EXECUTION 3 - With two contacts, both normally closed (NC);
- EXECUTION 4 - With two contacts that are normally open (NO);
- EXECUTION 5 - With two contacts, when one of them is normally closed (NC), and the second is normally open (NO);
- EXECUTION 6 - With two contacts, when one of them is normally open (NO), and the second is closed (NC).
3.1. Signaling pressure gauges. General concepts and operating principles
3. ALARM MANOMETERS
Signaling (electric contact) pressure gauge devices get their name from the main functions they perform - signaling that the set values of controlled pressure are exceeded or decreased. The operating principle of such devices is to close or open electrical contacts during the process of increasing or decreasing the measured (controlled) pressure. This determines their parallel name of electric contact. These devices are constantly being improved, parameters are being optimized, new designs are being developed/3-1…3-8, etc./.
Closing or opening electrical contacts is also used to turn on or off various technical devices, including automatic or automated control systems, control devices for various technological processes.
In previous works, the author most often used the term “signaling”, as recommended by GOST 2405-88, but which does not limit the use of the term “electrical contact”. In recent years, as the practice of communicating with industry representatives has shown, the term “electrical contact pressure gauges” has become widespread, which prompted the author to also use it in this work.
Some terms given in the chapter below are specific to the section of signaling (electrical contact) pressure gauge devices, and their wording, according to GOST 2405-88 /3-9/, is presented below.
Direct signaling device
– a device whose electrical circuit contacts are closed and opened without energy conversion.
Indirect signaling device
- a device whose electrical circuit contacts are closed and opened by converting energy from one to another.
Signaling device indicator
– an element of a signaling device, the position of which relative to the scale marks determines the deviation of the monitored parameter from the norm.
Alarm device triggered
- an action consisting of closing and opening an electrical circuit.
Setpoint
– the specified value of the controlled parameter at which the signaling device is triggered.
Setting range
– zone of the controlled parameter within which the setting can be made.
Normally closed (normally closed) contact
– a switched contact that closes (opens) the electrical circuit when the set value is reached.
Electrical contact (signaling) groups are produced with mechanical contacts, contacts with magnetic preload, inductive pairs, microswitches, and with electronic elements and other options for manufacturing a signaling device, a more detailed description of which is given below.
Electrical contact group with mechanical contacts
structurally the simplest (Fig. 3.1). The indicator of the signaling device 1 is movably mounted on a dielectric base with an electrical contact 2 fixedly fixed on it. The position of the indicator 1 on the dial of the device changes, its movement is carried out by a circular action on the stop 3. The mechanism of such influence will be described below.
| A) | b) |
Fig.3.1. View of a signaling device with mechanical electrical contacts (normally closed) in a closed state (a) and in a forced open state (b): 1 – indicator of a signaling device;
2 – pointer contacts; 3 – stop for moving the pointer; 4 - moving contact; 5 – pointer contact output; 6 – moving contact output.
Movable contact 4 is mechanically connected one-sidedly to the pointer of the pressure gauge through an additional driver. This connection allows, when moving the arrow, to break or connect an external electrical circuit that is opened or closed by electrical mechanical contacts 2 and 4, galvanically connected to outputs 5 and 6, respectively.
Mechanical contacts, made in the form of petals and struts, must have a durable coating in order to ensure stable operation under electric arc conditions. Such coatings can be the following metal alloys: silver-nickel (Ar80Ni20), silver-palladium (Ag70Pd30), gold-silver (Au80Ag20), platinum-iridium (Pt75Ir25), etc. Some manufacturers use cheaper alloys to coat contacts, which can significantly affect the reliability of the device. For example, in /3-8/ problems of mechanical contacts such as burning, false operation, and sticking are given. The nature of such phenomena may be as follows.
In mechanical electrical contact groups, pressure spiral springs with a certain turning moment are installed. The magnitude of this moment should be correlated with the magnitude of the traction force of the SE. Increasing this torque in order to ensure a stronger mechanical connection of the contacts leads to an increase in the error of the device. Traditionally, the turning moments for the spiral springs of mechanical signaling groups of indicating pressure gauges are: 1.2 mN/m - soft, 1.6 mN/m - normal and 8.5 mN/m - elastic. Accordingly, the operation of the signaling group (turning moments, contact actuation accuracy) largely depends on the design features determined by the manufacturer.
Devices with mechanical contacts are designed for voltages up to 250 V and can withstand a maximum breaking power of up to 10 W DC or up to 18 VA AC. Low breaking power of contacts can provide mechanical electrical contact groups with sufficiently high operating accuracy (up to 0.5% of the full scale value).
Magnetic contacts provide a stronger electrical connection
(Fig. 3.2).
Rice. 3.2. Type of mechanical electrical contacts with magnetic preload:
1 – pointer; 2 – pointer contact; 3 – moving contact; 4 – magnet.
Typical assemblies and parts for mechanical contacts: pointer 1, pointer contact 2, moving contact 3. The fundamental difference is the installation of magnet 4 in the contact circuit. Magnet 4 is mounted on the mechanical base of pointer 1. The main function of magnet 4 is mechanical pressure of the moving contact by a magnetic field 3 to the pointer contact 2. This pressing by the magnet 4 of the movable contact 3 occurs without a galvanic connection between them, but the distance between them is determined by the amount of mechanical impact on this pressing.
The magnet on the mechanical base of the pointer can be mounted motionless. However, some manufacturing companies attach it to a threaded shell. This allows the axial rotation of the magnet to move it relative to the moving contact and thereby regulate the mechanical strength of the two contacts of the electromechanical group.
The maximum breaking power of mechanical contacts with magnetic preload of the signaling device is up to 30 W DC or up to 50 VA AC and voltage up to 380 V. Due to the presence of magnets in the contact system, the error increases accordingly and reaches 2...5%.
A type of signaling device with two pairs of mechanical contacts is shown in Fig. 3.3.
Fig.3.3. Type of signaling device with two contacts: 1 and 2 – indicators of the signaling device; 3 – base; 4 and 5 – pointer contacts; 6 and 7 – contact outputs; 8 – general output; 9 – leash; 10 and 11 – moving contacts; 12,13 – mounting holes.
Two typical signaling device indicators 1 and 2 are movably mounted on base 3. Contacts 4 and 5 are fixed on the mechanical bases of indicators 1 and 2. External electrical circuits are connected to outputs 6 and 7, fixed on base 3 and galvanically connected to contacts 4 and 5. The operation of the two groups of electrical contacts is based on the third electrical output 8.
The main movable element of the signaling device is the leash 9, which is mechanically connected to the pointer of the pressure gauge and, when this arrow moves, moves the movable contacts 10 and 11.
Holes 12 and 13 are intended for mounting a signaling device on the dial of a pressure gauge.
Accordingly, if we virtually imagine the position of the leash 9 in the initial position of the scale, then we can testify from Fig. 3.3 that the presented electrical contact group has a first normally closed and a second normally open contact.
Signaling devices can be mounted in a single housing with a pressure gauge, and such designs are described in the next paragraph, or they can have a self-contained transparent plastic shell, as shown in Fig. 3.4, and are independently attached to the body and holder or dial of the device. Typically, such designs are called “electrical contact attachment” - Ek, industrial versions of which are presented in the next section.
| A) | b) |
Fig.3.4. Type of signaling devices for pressure gauges 100 (a) and 160 mm (b) in transparent plastic shells: 1 – lead fork; 2 – rotating device; 3 – contact outputs.
Lead fork 1 (Fig. 3.4a) is intended for mechanical connection of the signaling device with the pressure gauge. In this design, when installing a signaling device, the driver of the movable contacts moves into the gap of plug 1. There may be designs with a metal loop instead of the driver.
Translation of the signaling device indicators is provided by rotary device 2 (Fig. 3.4a,b). In the normal state, turning the pin of this device moves one pointer, and when pressed, the second one.
The convenience of the signaling device shown in Fig. 3.4b is the ability to connect contacts 3 to the outputs and disconnect external electrical lines from them without dismantling the entire group.
Mechanical contacts with magnetic preload, depending on the quality of their surface, have the same disadvantages as contacts without magnetic preload.
Circuits with inductive contacts
electrical contact (signaling) pressure gauges are based on the interaction of the magnetic field of the inductive block
2
with the metal plunger
1
(Fig. 3.5). Accordingly, this type of device requires additional external power.
Signaling groups with inductive contacts for pressure gauge instruments are manufactured in two versions: with an external plunger (Fig. 3.5, a
) and a plunger located inside the block (Fig. 3.5,
b
).
Electrical contact devices based on inductive blocks with external plungers ensure the functioning of the electrical circuit at a constant voltage of 5-25 V and a maximum current of up to 3 mA.
Rice. 3.5. Diagram and type of inductive contacts of an electric contact pressure gauge:
A
– with an external plunger;
b
– with an internal plunger;
1
– plunger;
2
– inductive block
The internal arrangement of the plunger ensures the circuit operates at a constant current of up to 1 mA. The accuracy class of such systems does not exceed 0.5. The inductive unit is mounted on an additional movable support - the base contact, and the role of the plunger is performed by both the main and additional arrows. One of the options for such a group is shown in Fig. 3.6.
Fig.3.6. Type of signaling group with inductive contacts:
1 – inductive unit; 2 – indicator of the signaling device; 3 - plunger; 4 – index arrow.
The inductive unit 1 is rigidly fixed to the indicator 2 of the signaling device. Moving the pointer 2 leads, accordingly, to moving the inductive unit 1.
The plunger 3 is mechanically fixedly connected to the index arrow 4. When the pressure changes, the movement of the index arrow 4 leads, accordingly, to the movement of the plunger 3. The entry of the plunger 3 into the slot gap of the inductive block 1 leads to the closure or opening of the switching electrical circuit.
In domestic industry, electrical contact pressure gauges with inductive units are not used widely enough due to the need for power supply, although abroad they are used to control explosive environments and organize circuit switching in aggressive environmental conditions.
Pressure gauges with pneumatic contacts are similar to the previous ones, but instead of inductive blocks, pneumatic sensors are installed, which, under the influence of a plunger, when a given pressure is reached, close or open the pneumatic line.
The disadvantages of the above devices have led to the search for new solutions in organizing the functioning of electrical contact groups.
Reed switch –
abbreviated name for “
hermetic
contact
”/3-10/
. This is a magnetically controlled electromechanical device that includes a pair of ferromagnetic contacts sealed in a sealed glass bulb. When approaching the reed switches of a permanent magnet, the contacts, depending on the design, close or open. When translated, some experts call reed switches as electronic contacts
. The operating principle of reed switches is shown in Fig. 3.7. Contacts are inserted into a small-sized glass flask 1, sealed and filled with an inert gas (Fig. 3.7a): O – common, NC – normally closed, NO – normally open (open). The common contact O in the bulb has a continuation in the form of a movable petal 2. Without the influence of an external magnetic field, the movable petal 2 with the NC contact forms a closed circuit (Fig. 3.7a).
Fig.3.7. Schematic diagram of electronic contacts in a neutral state (a) and
when exposed to a magnetic field (b):
1 – glass flask; 2 - movable petal.
When exposed to an external magnetic field (Fig. 3.7b), the movable petal 2 closes the electrical circuit with the NO contact, which was not closed without an external magnetic field.
Electronic contacts operate without external electrical power, operate at low currents and voltages and have a breaking power of up to 60 Watts. Coating the contacts directly with rhodium, as well as filling the glass ampoule with inert gas, ensures high reliability of their operations. In normal operating modes, the number of operations reaches 106...107. At low voltage (up to 5 V - sparking threshold), the number of operations increases to 109.
The hysteresis of electronic contacts is limited to 3...5%.
The contacts are lightweight and have advantages over mechanical contacts when operating under conditions of increased vibration.
Figure 3.8 shows a view of an industrial version of a signaling group with electronic contacts.
Fig.3.8. View of an industrial version of a signaling device with electronic contacts.
The design of the industrial version provides for the closing or opening of the electrical circuit when the set point is reached and maintains this position with a further increase in pressure. An industrial signaling device, as can be seen from Fig. 3.8, has traditional indicators and the corresponding versions shown in Fig. 3.11 (see below).
Electrical contact groups on mechanical microswitches
developed on the basis of the traditional tribic-sector mechanism (Fig. 3.9).
Fig.3.9. View of the tribco-sector mechanism with installed mechanical microswitches:
1 – sector axis; 2 – sector shank; 3 – cams; 4 – rocker arms; 5 – microswitches; 6 – sector of movement of microswitches; 7 – mechanism for fixing settings.
Cams 3 are mounted on axis 1 of the sector with shank 2. These cams are connected through rocker arms 4 to microswitches 5. Setting the microswitches to the specified setpoint values is organized using sector 6 of moving microswitches and locking mechanism 7.
Thus, the rotation of the axis of sector 1 through the cams 3 leads to the movement of the rocker arms 4 and the turning on or off of the microswitches 5. Adjustment of the operation of the signaling device comes down to the optimal choice of the position of the cam on the sector axis.
Figure 3.10 shows a cross-sectional view of a microswitch.
Fig.3.10. Cross-sectional view of the microswitch: 1 – housing; 2 - elastic spring contactor; 3,4 – opening and closing terminals, respectively; 5 – general conclusion; 6 – lever; 7 – pusher;
One end of the spring-loaded contactor 2 is rigidly fixed in the housing 1. The second end of the contactor 2 with contacts installed on it on both sides moves abruptly between the contacts of the opening and closing terminals 3 and 4, respectively.
The end of the spring-loaded contactor 2 is rigidly fixed in the housing 1 using a common terminal 5 galvanically connected to this contactor.
Under external influence, lever 6 moves the pusher 7 and mechanically acts on the elastic part of the contactor 2. Under threshold influences of this pusher, an abrupt movement-deflection occurs - collapse of both the elastic part of the contactor 2, with one end rigidly fixed and a limited stroke of its middle, and an abrupt movement the free end of this contactor with contacts installed on it on both sides. These contacts are included in a mechanical and electrical connection with the contacts of the 3-break and 4-close pins. When electrical contact of contactor 2 with common terminal 5 occurs, respectively, opening or closing with terminals 3 and 4 occurs. Thus, under the influence of lever 6, electrical circuits with terminals 5-3 and 5-4 are opened or closed, respectively.
The contacts of terminals 3 and 4, as well as the contacts of contactor 2, are made of noble metals. In EKM Vm models, microswitch contacts are made of pure (99.9%) silver. This allows the signaling device to operate with microswitches at an electrical voltage of up to 380 V at an operating current of up to 5 A. The design features of the microswitches make it possible to avoid sticking and burning of contacts and false operation. Ensure stable operation of the signaling device in conditions of increased external vibrations.
High breaking electrical power allows pressure gauges with such microswitches to be included directly in the signaling and control circuits of many technological processes.
Traditionally, electric contact pressure gauges are made on the basis of indicating instruments with a tubular Bourdon spring or a multi-turn sensing element. But this is for medium and high pressures. At low pressures, stable operation of the electromagnetic mechanism requires sufficient traction forces, which is not inherent in tubular sensitive elements. At low pressures, the main sensitive element of deformation electric contact pressure gauges is membranes or membrane boxes. The basic designs of such devices are described in the next section.
Circuit diagrams
electrical contact (signaling) pressure gauge devices, according to the main current GOST 2405-88/3-9/, are shown in Fig. 3.11.
Rice. 3.11. Schematic electrical diagrams of electrical contact (signaling) pressure gauge devices: a
– single-contact short-circuit (according to GOST 2405–88 – Version I);
b
– single-contact opening (Execution II);
c – two-contact open-open (Execution III); g
– two-contact for short-circuiting (Version IY);
d
– two-contact open-close (Version Y);
e
– two-contact for short circuit-open circuit (Version YI);
1
– index arrow;
2
and
3
– electrical contacts of the pointer;
4
and
5
– zones of closed and open contacts, respectively;
6
and
7
– objects of influence
A typical operating diagram of an electrical contact pressure gauge device can be illustrated in Fig. 3.11 a (Esp. I )
.
When the pressure increases and reaches a certain value, index arrow 1
with a movable electrical contact enters zone
4
and closes the electrical circuit of the device using index contact
2
. Closing the circuit, in turn, leads to the commissioning of the affected object 6.
In the opening circuit (Fig. 3.11 b, Use II
) in the absence of pressure, the movable electrical contacts of the indicator arrow
1
and the base contact of the indicator
2
are closed.
The electrical circuit of the device and the object of influence are under voltage U. When the pressure increases and the pointer passes the zone of closed contacts, the electrical circuit of the device breaks and, accordingly, the electrical signal sent to the object of influence is interrupted.
Most often, in production conditions, pressure gauges with two-contact electrical circuits are used: one is used for sound or light indication, and the second is used to organize the functioning of various types of control systems. Thus, the open-close circuit (Fig. 3.11 d, Use III
) allows through one channel, upon reaching a certain pressure, to open one electrical circuit and receive a signal of influence on the object
7
, and through the second, using the base contact
3
, to close the second electrical circuit, which is in an open state.
Closing-opening circuit (Fig. 3.11 e, Use IY
) allows, with increasing pressure, to close one circuit and open the second.
Two-contact circuits for short-circuiting (Fig. 3.11 d, Use Y
) and opening-opening (Fig. 3.11
c, Use YI
) ensure that when the pressure increases and the same or different values are reached, both electrical circuits are closed or, accordingly, opened.
A description of the models of signaling (electrical contact) pressure gauge devices based on the groups described above is presented below.
Advantages and disadvantages
Like any technical devices, ECMs have their advantages and disadvantages.
- Limitation of load power due to too low value of the limiting switching current, which has a range from 0.3 to 0.5 A (ECM with sliding contacts) to 1 A (contacts with magnetic preload);
- High cost, compared to a pressure switch, the price can be two or three times more.
- Visualization of settings is clear and understandable;
- Setting the response limits is quite simple and does not require special keys, special knowledge or a lot of time;
- Assembly in a single housing, which eliminates the need to use additional tees when connecting.
Advantages of ECM pressure gauges
A high-tech pressure gauge with an electrical contact attachment is used in equipping water supply systems, heating networks, ventilation systems, in industry and mechanical engineering. It is needed to control pumps and valves, as a more reliable version of the standard pressure switch.
The EKM pressure gauge can be used in everyday life and in low-rise construction. Many water supply systems cannot operate reliably and safely without this device. The advantages of installing them in the system:
- simple installation method;
- convenient layout and compact durable body;
- adjustment according to the parameters of the controlled system;
- good visualization of settings and indicators;
- reliability and durability.
You can buy an electric contact pressure gauge in batches of any quantity starting from one unit. The simplicity and accuracy of operation of the device ensure its stable demand.
In our online store, the price for an EKS pressure gauge is set without extra charges, because we are official representatives of most domestic manufacturers. All products are guaranteed. We will not only help you select the device according to its parameters, but will also provide consultation on its further operation.
Brief overview of some sensor models and their features
TM-510R.05, TM-510R.06
TM-510R.05 , TM-510R.06 are assembled on the basis of TM-510 pressure gauges, and after installing the electrical contact attachment they become full-fledged ECM.
These ECM models use contacts with magnetic compression, which allow switching high currents with high breaking power of the contacts, compared to devices with sliding contacts.
EKM TM-510R.05 , TM-510R.06 are characterized by a reliable electrical connection under dynamic loads.
- Two-pin electrical circuit;
- Maximum possible voltage
380 V;
- The maximum possible current is 1 A ;
- The maximum possible breaking power of the contacts is 30 W ;
