PI-regelaar met display voor klepaandrijving | 0-2000 Pa | 2

The DPSA-2 series are high resolution differential pressure controllers with display. The integrated PI control with anti-windup function allows direct control of valve actuators. They are equipped with a fully digital sensor element and are designed to be used in a wide range of applications. Zero point calibration and reset of the Modbus registers can be performed via a microswitch. They also have an integrated K-factor and an analogue / modulating output (0—10 VDC / 0—20 mA / 0—100 % PWM). All parameters are accessible via Modbus RTU. This device operates on 18-34 VDC / 15-24 VAC ±10 %. The controller operates in the range of 0 to 2,000 Pa.

Constant pressure, air volume flow or air velocity?
This differential pressure controller controls damper actuators. The damper position is controlled to keep the differential pressure [Pa] constant at the set point. The working range is 0 to 2,000 Pa. It is also possible to control the damper position based on air volume [m³/h] or air velocity [m/s]. Use the optional connection set type PSET-PVC-200 or PSET-QF-200 to control the air volume based on the K-factor of the fan. This connection set can also be used to control differential pressure. To control the air volume based on duct cross-section [cm²] or air velocity [m/s], use the optional connection set type PSET-PTS-200 or PSET-PTL-200. The set point can be adjusted via Modbus RTU.

What is the difference between a differential pressure sensor (or transmitter) and a differential pressure regulator?
The output signal of a differential pressure sensor (or transmitter) increases proportionally within the set range. So at a differential pressure of 0 Pascal the output is 0 Volt, and at 1,000 Pascal the output is 10 Volt.
If it were CO2 or relative humidity, it would be perfectly possible to control the speed of a fan or the position of a valve in this way: The more CO2, the more ventilation. Or the more moisture, the further the exhaust valve opens.
However, if it is differential pressure, it is unlikely that proportional control is used. Usually, pressure control does not work within a range, but rather at a set value, a "set point". A differential pressure regulator will then continuously adjust a fan or control valve, in such a way that the desired pressure - the set set point - is maintained.
Summary:
A sensor (transmitter) measures: and this measured signal is then used to monitor the differential pressure, or to use as a measurement signal for an external controller.
A controller (PI controller) controls: somewhere within the range of the sensor you program a set point. And the differential pressure controller will control the fan or valve via its output in such a way that the value it measures corresponds to the desired set point.
Autotune
This differential pressure controller works with a so-called PI control. And such a PI control is quite complicated to set. But fortunately, the Sentera differential pressure controllers are equipped with an autotune function. You only have to determine the desired set point and the controller does the rest. We will go into this in more detail below, but you can safely skip this part.

How does a PI control work?
A PI control can best be viewed as a kind of "loop". The differential pressure regulator (just like a transmitter) continuously performs measurements. The difference with a transmitter, however, is that its output does not increase proportionally as the differential pressure increases. But, it continuously adjusts its output (and therefore also the fan or valve), in order to obtain the desired set point as a measured value.
Initially - immediately after starting from standstill - the measured value will be far removed from the desired value (the set point). The controller will then react violently (resulting in major changes in the speed of the fan). As a result, it goes very quickly to the set point. Probably even beyond it, causing it to quickly reduce the speed again. But slightly less violently than the first movement. Eventually, these fluctuations will decrease in proportion and "land" on a nice stable signal that corresponds to the set value. You now have a stable fixed differential pressure.
As pressure drops or builds up, the output of the controller is automatically corrected. In order to maintain the set point.
Incidentally, a delay is also built into a PI control. In such a way that at the slightest pressure difference (e.g. someone opening a door), the fan does not start to compensate excessively. The delay gives it time to correct calmly. Because, there is nothing as annoying as a pressure control that is set "too" reactively. But thanks to the AutoTune function, you will not have this problem.

Praktische toepassingen : CAV-regeling
Eén van de praktische toepassingen van een verschildrukregelaar voor kleppen is een CAV (Constant Air Volume) regelsysteem:
Stel u een netwerk voor van ventilatiekanalen waarbij één grote dakventilator gebruikt wordt om vervuilde lucht af te voeren uit verschillende kamers die elk voorzien zijn van een instelbaar luchtrooster (regelklep).
Door middel van de HPSA verschildrukregelaar opent elke kamer zijn afzuigklep in functie van het gewenste (meestal voorgeschreven) debiet. Als er wijzigingen in het kanalen netwerk ontstaan door ingrepen in andere kamers of door het veranderen van de ventilatorsnelheid, gaat de HPSA regelaar bijsturen tot het gewenste debiet voor die specifieke kamer correct is.
Meestal gaat een PI-verschildrukregelaar (type HPSP) in het hoofdkanaal (waar alle andere kanalen samen komen) de snelheid van de dakventilator automatisch aanpassen teneinde de druk in de leiding constant te houden, onafhankelijk van hoeveel kamers lucht vragen.
Verschildruk, luchtvolumestroom of luchtsnelheid?
Technisch gezien regelt deze verschildrukregelaar enkel de verschildruk [Pa]. Maar op basis van deze meting in Pascal kan het toestel zelf het luchtdebiet [m³/h] of de luchtsnelheid [m/s] berekenen.
Om te regelen op luchtdebiet [m³/h] zijn er 2 mogelijkheden:
Ofwel beschikt u over de K-factor van uw ventilator. In dat geval volstaat het die waarde in te geven in het daarvoor voorziene Modbusregister. Verder voert u gewoon een drukmeting uit. Dus met behulp van de aansluitsets PSET-PVC-200 of PSET-QF-200. Het luchtdebiet wordt automatisch uitgerekend en u kan het uitlezen via de Modbusregisters.
Indien u niet beschikt over de K-facor van uw ventilator, of de opstelling laat niet toe om die op een betrouwbare manier te gebruiken, is er ook de mogelijkheid om een meting van de luchtsnelheid [m/s] uit te voeren. Meestal is dit eenvoudiger uit te voeren. Hiervoor heeft u dan de optionele PITOTbuis-aansluitset nodig: PSET-PTS-200 of PSET-PTL-200. Omdat u op luchtsnelheid [m/s] wil regelen, is het noodzakelijk om de kanaaldoorsnede [cm²] in te voeren in Modbus, waarna u het luchtdebiet [m³/h] opnieuw kan uitlezen via Modbus.
Het setpunt kan dus zowel in Pascal, m³/h als m/s worden ingevoerd.

7-segment LED scherm
Het 7-segment LED-display geeft de verschildruk, het luchtvolume of de luchtsnelheid weer. Bovendien beschikt deze verschildruktransmitter over duidelijke groene, gele en rode LEDs. De groene LED geeft aan dat het de gemeten waarde binnen het ingestelde bereik ligt. Wanneer de meetwaarde binnen het waarschuwingsbereik komt, gaat de gele LED branden. En rood betekent dat de waarde buiten het bereik ligt. De tweede groene LED geeft de sensorstatus aan. Hij wordt geactiveerd wanneer de voeding en Modbus RTU-communicatie zijn ingeschakeld.

Analogue output for controlling an EC motor, frequency controller or valve actuator
This controller transmits the EC fan speed (or the control signal for the AC fan speed controller) via its analogue output. This can be a 0-10 VDC control signal, but you can also change this to 0-20 mA or 0 to 100% PWM via Modbus.

Setting via Modbus
All parameters can be set via Modbus RTU

Reduced installation time
The power supply, analog output and Modbus RTU communication are connected via the terminal block with spring clamps. This eliminates the need for routine checks and guarantees reliable contact. For both stranded and hard core wires.

This differential pressure regulator operates on 24 VAC / 24 VDC
The device operates on 24 VAC or 24 VDC The terminals (V-) of the power supply and (GND) of the output are internally connected. This means that only 3-wire operation is permitted. This makes this transmitter suitable for use in existing 3-wire installations. Be sure to also view the Sentera power supplies. Be sure to also view the Sentera power supplies.

High-quality housing
The housing is made of high-quality r-ABS VO (UL94) plastic. This material is heat-resistant and offers good protection against impacts. The connections for the pressure lines are made of aluminum. The housing offers IP65 protection against the ingress of dirt and water. This sensor can be mounted on the wall.