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IP rating, sometimes referred toas International Protection rating, or Ingress Protection rating classifies the degree of protection provided by the drive enclosure against both solid objectsand liquids. The IP code, defined by International standard IEC 60529, generally consists of two digits that classify the level of protection providedin each case.

Sentera products are available in enclosures with different IP ratings, dependent of the model range andspecifications required. Consult the product datasheets for further information on available ranges. A summary of the available IP ratings for Sentera productsare given below.

IP20 Enclosures provide someprotection from accidental contact from hands / fingers and no protection against the ingress of dust, water or other liquids into the product’s enclosure.These devices are designed to be installed in an electrical cabinet with sufficient ventilation and cooling possibilities.

IP30 Enclosures provide protectionagainst contact from hands / fingers and smaller objects (e.g. screwdriver). They don’t offer protection against the ingress of dust, water or other liquids into the product’s enclosure. These devices are designed for indoorapplications.

P54 Enclosures protect againstingress of dust to the point of preventing ingress of anything potentiallyharmful to the internal workings of the device. On top of that, the enclosure also withstands water splashing from different directions (no water jets). These devices are designed for applications in harsher environments or outside if protected against rain and direct sunlight with a cover.

IP65 Enclosure is rated ascompletely dust tight and protected against exposure to water jets from anydirection. These devices are designed for outdoor applications.

The level of IP protection you will require is dependent on your application and the conditions the Sentera device will be exposed to, and by any local regulations that are applicable to your application. Generally, if unsure, then always seek advice and elect to go with the higher IP rating.
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PWM or “Pulse Width Modulation” (also known as “Pulse Duration Modulation” or PDM), is a modulating control signal, comparable to an analogue 0-10 VDC or 0-20 mA signal. It can be used to send the requested rotational speed to an EC motor or AC fan speed controller. Another application example is to transmit the requested position to an actuator powered damper.

Typically, the EC fan speed will increase in proportion to the value of the analogue 0-10 VDC or 0-20 mA signal. For a PWM signal – a continuous train of electronic pulses consisting of a HIGH and LOW part - this works as follows:
- The frequency of the PWM signal determines the duration of one complete HIGH / LOW cycle. For example, a frequency of 1.000 Hz means: every second, the PWM signal counts 1.000 HIGH / LOW cycles.
- The comparison of the duration of the HIGH part, compared to the FULL signal (expressed in percent and also called “duty cycle”) determines the speed at which the motor or fan should run or in case of an actuator powered damper, the requested position.

A power supply is required to generate a PWM control signal. Most Sentera devices with analogue output feature an integrated power supply (3,3 VDC or 12 VDC), but in case the EC motor requires a PWM signal with a specific amplitude, an external power source should be applied.

So when using a Sentera device to control a fan (or actuator powered damper) via PWM, make sure that both the frequency (in Hz) and the amplitude (in VDC) of the modulating output of the Sentera device correspond to the frequency and amplitude requested by the external device.

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What is PI-Control?
PI Control is a feedback control loop mechanism that calculates a correction by taking the difference between the desired set point and the measured value. Common applications are cruise control, temperature control, etc.

The controller's PI algorithm restores the measured value to the desired set point with a minimal delay and
- The P stands for proportional and represents the size of the calculated correction. The closer the measured value is to the set point, the smaller the corrections must be.
- The I stands for Integral and looks at how the difference between set point and measured value evolves in time when applying the correction.

Both P & I are parameters that can be set manually in the PI-controller. When activated (and available), the auto-tune function of the PI Controller calculates the optimal P- and I-parameters based on the real-time response of the process to different control values.
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We recommend that the total cable length per segment does not exceed 1.000 m. (Total cable length = sum of the main network line and all branches).

Modbus RTU should follow a line topology, so avoid making branches on the main line. If branches are present, they should be kept as short as possible. The combined length of all branches should not exceed 20 m.

When the total cable length becomes too high, the Modbus RTU communication will be disturbed. To compensate these communication losses due to cable length, a Modbus repeater (e.g. DPOM-24-20) can be used to compensate cable length.
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Sentera advises to use Shielded Twisted Pair (STP) or Unshielded Twisted Pair (UTP) cable to connect Sentera devices via Modbus RTU.

The wires should have the following characteristics:
- Characteristic impedance: 120 Ω ±10%
- Specific resistance depending on network length

Modbus RTU has a line topology - the Modbus RTU should be connected from device to device and branches should be minimised.
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Sentera devices can be connected together via ‘PoM’ or ‘Power over Modbus’. This means that both Modbus RTU communication and 24 VDC power supply are distributed via one Unshielded Twisted Pair (UTP) network cable.

Larger networks containing many devices, should be split into different segments. For each segment, the total current consumption must remain limited to 1,5 A maximum.

To select the correct power supply, calculate the total sum of the maximum current consumption of all connected devices in the segment. Select a power supply with sufficient capacity to provide power supply to all connected devices, based on this sum. We advise to use not more than 90 % (*) of the maximum capacity of the power supply to compensate power losses in the cables and inrush currents during start up.

(*) Depending on the products connected to the PoM network.

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All Sentera devices with Modbus RTU communication can be used standalone or they can be integrated in a Modbus RTU network. In many situations, the default parameter settings will be enough to start using the product. For the applications where some parameters need to be adjusted or optimised, we advise you to use Sentera’s free 3S Modbus software. Connect the Sentera device to your computer and the 3S Modbus software will automatically recognise the connected device. The Modbus input registers are read-only, the holding registers can be modified.
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In the past, many devices were based on analogue technology, featuring jumpers or dip switches to make all required settings. With this older, analogue technology, it was no longer possible to achieve and sustain high measurement resolutions and to make these measurements available via the internet.
As befits an innovation leader, Sentera started the development of a completely digital HVAC transmitter without dip switches and jumpers. All settings can be made via Modbus RTU – locally or remote. Actually, it is much easier than before: install the free 3S Modbus software on your computer, connect the Sentera device to your computer via the USB key (article code CNVT-USB-RS485) and double click to adjust the parameters.

All parameters can be adjusted via the Modbus RTU holding registers or monitored via the input registers (download the Modbus RTU register maps for more details).
In case you don’t want to use a computer, try our SENSISTANT Modbus configurator.
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Sentera offers devices to measure or control following parameters: temperature, relative humidity, CO2, air quality (TVOC), CO, NO2, ambient light, differential pressure, volume flow and air velocity.

transmitter or sensor is a device that measures a certain parameter. The device translates this measured value into an analogue output (0-10 VDC / 0-20 mA / PWM) or Modbus RTU register.

An intelligent sensor has the possibility to define different ranges for different parameters. These types of sensors only have one single output. When all measured values are at their minimum range, the sensor output will remain at its minimum value. When one of the measured values approaches the maximum range, the sensor output will also increase towards its maximum. This functionality makes it possible to control air flow in function of different parameters with a simple, intelligent sensor. The parameter with the narrowest range has the highest influence on the sensor output.

A sensor controller offers the possibility to define a setpoint (via Modbus RTU). By controlling its output, the sensor controller will try to keep the measured values as close as possible to the setpoint values.

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The insulation of the motor windings prevents short circuits in the windings or connection of the winding to the protective earth. The class of insulation of a motor winding defines the strength of insulation required with respect to maximum temperature rise of the motor. Different motor types have different temperature rise characteristics in function of the duty cycle and the size of the motor enclosure. Usually Class F insulation (or higher) is suitable for VFD use.
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In both induction and synchronous motors, the AC power supplied to the motor stator windings create a magnetic field that rotates in time with the AC oscillations.

The rotor of a synchronous motor is equipped with permanent magnets. A PMSM (Permanent Magnet Synchronous Motor) uses permanent magnets embedded in the steel rotor to create a constant magnetic field. The stator carries windings produce a rotating magnetic field. At synchronous speed the rotor poles lock to the rotating magnetic field. These motors are not self-starting and therefore they need to be combined with a frequency inverter to be able to operate them.

The magnetic field in the rotor of an induction motor is created solely by induction instead of being self-magnetized as in permanent magnet motors. For rotor currents to be induced, the speed of the physical rotor must be lower than that of the stator's rotating magnetic field; otherwise the magnetic field would not be moving in relation to the rotor conductors and no currents would be induced. As the speed of the rotor drops below synchronous speed, the rotation rate of the magnetic field in the rotor increases, inducing more current in the windings and creating more torque. Under load, the speed drops and the slip increases enough to create sufficient torque to turn the load. For this reason, induction motors are sometimes referred to as asynchronous motors.

For induction motors, following international efficiency standards have been defined: IE1, IE2, IE3, IE4 and IE5. Synchronous motors are often referred to as PMSM (Permanent Magnet Synchronous Motors), BLDC (Brushless DC) motors or SyncRM (Synchronous Reluctance Motors).
All these types of motors can be controlled via our frequency inverters.
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A Sentera frequency inverter (or VSD - Variable Speed Drive) allows you to control the speed of AC synchronous motors. Frequency inverters generate an almost perfect sinusoidal motor voltage via PWM (Pulse Width Modulating) technology using IGBT's (Insulated Gate Bipolar Transistors). The ratio of voltage to frequency is kept constant, resulting in an optimal motor control and very silent operation of both motor and frequency inverter.
Available for single or three phase motors up to 46 A.

The desired motor speed can be adjusted manually via a knob (local or remote control) or in function of CO2, air quality or another parameter (demand based). In this second scenario, an HVAC sensor is connected to the fan speed controller to calculate the optimal fan speed. More information can be found on the Sentera solutions page.
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An EC motor (Electronically Commutated motor) can be seen as an AC motor with integrated fan speed controller.
This means that an EC motor requires an indication of the desired fan speed or a fan speed setpoint. The most common ways to provide this information to the EC motor are:
- Potentiometer that sends a 0-10 VDC (analogue) signal to the EC motor (*)
- HVAC sensor that sends a 0-10 VDC (analogue) signal to the EC motor (*)
- HVAC sensor that sends the desired fan speed via Modbus RTU to the EC motor (**)
- HVAC controller that sends the desired fan speed via Modbus RTU to the EC motor (**)

(*) Some Sentera devices can also generate a 0-20 mA or PWM signal.
(**) In this case, an EC motor with Modbus RTU communication is required. The motor type should be compliant with Sentera PoM devices.
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The best way to do this is via Modbus RTU. The advantages of this recent, digital technology is the immunity for interferences. Thanks to this technology, you will be able to use longer cables – up to 1.000 m - without the risk of losing information. Devices that are connected via Modbus RTU can exchange a lot of information – not only the desired fan speed – and it is also possible to monitor and control them via internet.

The older - analogue - technology is still present in many installations. In these installations, the desired fan speed is usually transmitted via 0-10 VDC / 0-20 mA or PWM. The disadvantage of this technology is the sensitivity for interferences. If cable lengths are > 10 m, the maximum value received at the other side of the cable will not be 10 VDC anymore due to cable resistance. Also power cables nearby the signal cable, EMC pollution or magnetic fields can disturb the analogue signal. And since only the desired fan speed is transmitted, there is no possibility to monitor the status of the connected device or other parameters via internet.

More information can be found on the Sentera solutions page.
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Yes, that is possible. If doing so, make sure that:
- All connected motors are identical.
- The fan speed controller is selected, based on the total motor current required, by adding together the rated current of all the connected motors. The selected fan speed controller must have a maximum current rating that is equal or higher than this sum.
- Each motor is protected by an individual thermal overload.
- The motors remain permanently connected to the fan speed controller and are not individually started or stopped whilst the fan speed controller is enabled.
- When using a frequency inverter: operate in V/F Mode only and apply an output filter.

In the scenario of one fan speed controller per motor, each motor can be controlled separately and run at a different speed. This is not the case when multiple motors are controlled via one fan speed controller. Secondly, running multiple motors from one fan speed controller creates a single point of failure.
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Kick start and soft start are two different ways to start up a motor or fan.
The best acceleration method depends on your application. Applications with high inertia might need a higher torque at start up to avoid stalling of the motor.

Kick start — the motor will accelerate immediately from standstill towards maximum speed.
The full motor torque is almost immediately available. After this start-up period (typically 8 – 10 s), the motor will decelerate towards the requested fan speed setpoint.
This starting method is often used to avoid motor stalling at low speed. The disadvantage is the mechanical stress at start-up and a high motor start current.

Soft start — the motor will smoothly accelerate from standstill towards the requested fan speed setpoint.
This starting method gives you the advantage of reduced mechanical stress and lower motor starting currents.
Due to the reduced motor torque during start up, this acceleration method is not ideal for high inertia applications.

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A motor which is referred to as ‘AC motor’ has a stator winding. The AC power supplied to the motor stator creates a magnetic field that rotates in time with the AC oscillations. This magnetic field is used to generate the motor torque. AC motors (and certainly induction motors) are relatively cheap and have a simple construction, compared to DC motors. At the other hand, DC motors offer a very high energy efficiency.

Brushless DC motors are also known as EC motors (or Electronically Commutated motors). They are synchronous DC motors, powered by a DC electric source via an integrated fan speed controller which produces an AC electric signal to drive the motor. The integrated controller uses a DC current switched on and off at high frequency for voltage modulation and passes it through three or more non-adjacent windings. Because the controller must direct the rotor rotation, the controller requires some means of determining the rotor's orientation/position (relative to the stator coils). Some designs use Hall effect sensors or a rotary encoder to directly measure the rotor's position.

An EC motor can be seen as an AC motor with integrated fan speed controller. This means that an EC motor requires an indication of the desired fan speed or a fan speed setpoint. Many EC motors can be controlled via an analogue 0-10 VDC or PWM signal. More and more EC motors feature Modbus RTU communication. The advantage is that they cannot only be controlled via Modbus RTU, but all the motor parameters (Rpm, consumed power, motor status, motor temperature, etc.) are also available via Modbus RTU.

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