XS0 - Volume flow MODBUS | TROX GmbH

Bus interface Modbus RTU


Volume flow controller - static transducer


Control component for type TVE




Compact device for use with VAV terminal units TVE

  • Controller, static differential pressure transducer and actuator in one casing
  • Use in ventilation and air conditioning systems, only with clean and contaminated air
  • Simple terminal connection without the use of additional junction boxes
  • Volume flow rates qvmin and qvmax are pre-set in the factory and saved in the controller as adjustable parameters
  • High data transparency through standardised bus communication Modbus RTU, RS485
  • Setpoint value defaults, override controls, parameter adjustment via Modbus register
  • Integral display for volume flow rates, operating modes and setting of operating parameters
  • Service access for manual adjustment devices and PC configuration software


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General information


  • All-in-one control devices for VAV terminal units
  • Static differential pressure transducer, electronic controller, and actuator are fitted together in one casing
  • Static pressure transducer for broader range of applications with clean and contaminated air, e.g. extract air that contains dust and fluff
  • Suitable for different control tasks depending on the defaulting of the setpoint value
  • Variable volume flow rate control based on setpoint defaults coming from room temperature controller, central BMS, air quality controller or other sources via a communication
    interface or analogue signal
  • Override controls for activating qvmin, qvmax, shut-off, OPEN position via Modbus register or switch/ relay are possible (depending on the interface configuration)
  • Volume flow rate actual value is available as a network data point or linear voltage signal
  • Damper blade position is available as a network data point

Control strategy

  • The volume flow controller works independently of the duct pressure
  • Differential pressure fluctuations do not result in permanent volume flow rate changes
  • To prevent the control from becoming unstable, a dead band is allowed within which the damper blade does not move.
  • Flow rate range is set in the controller at the factory (qvmin: minimum volume flow rate, qvmax: maximum volume flow rate)
  • Operating parameters are specified via the order code and set in the factory

Operating modes

  • Modbus (M): setpoint value default via Modbus register
  • Analogue – variable operation (V): setpoint value default via analogue interface, signal voltage range corresponds to qvmin to qvmax

  • Analogue – constant value mode (F): no setpoint value signal required, setpoint value corresponds to qvmin


Communication interface

  • Modbus RTU, RS485
  • For data points, see Modbus register list

Analogue interface with adjustable signal voltage range

  • Analogue signal for volume flow rate setpoint value
  • Analogue signal for volume flow rate actual value (factory setting)
  • Alternatively: analogue signal for damper blade position (adjustment by others required)


  • Interface type according to operating mode pre-set in the factory
  • Can be adjusted by others using the communication interface (Modbus register) or display

Signal voltage ranges

When using the analogue interface

  • 0 – 10 V DC
  • 2 – 10 V DC

Parts and characteristics

  • Transducer for static pressure measurements
  • Overload protection
  • Terminals with cover
  • Display and operating elements for simple menu guidance
  • Menu guidance for adjusting operating parameters and communication interface
  • Service interface


  • TROVM-024T-05I-DS10-MB
  • Can only be used for type TVE


  • Due to the volume flow rates set in the factory, always ensure that the control units are only installed in the specified locations
  • Analogue interface: ready for use after installation and wiring
  • Modbus interface: additional commissioning steps required
  • Operating parameters can be adjusted by the customer (using the display, adjustment device or Modbus register)
  • Zero point correction not required

Useful additions

Adjustment device type GUIV3-M  (order code AT-VAV-G3)

Technical information

Function, Specification text, Order code


① Differential pressure transducer
② Actuator
③ Volume flow controller
④ Setpoint value via Modbus or analogue signal
⑤ Shaft with effective pressure channel

VAV terminal units control the volume flow in a closed loop, i.e. measurement - comparison - correction. This is done via a differential pressure sensor. An integral differential pressure transducer converts the effective pressure into a voltage signal. The factory setting is such that 10 V DC correspond to the nominal volume flow rate (qvnom). The volume flow rate setpoint value defaults from a higher-level controller (e.g. room temperature controller, air quality controller, central BMS). Variable volume flow control results in a value between qvmin and qvmax. It is possible to override the room temperature control, e.g. by a complete shut-off of the duct. The controller compares the volume flow rate setpoint value to the actual value and controls the integral actuator accordingly.


  • Compact controller for volume flow rate
  • Control according to a constant or variable volume flow rate setpoint
  • Electronic controller for applying a reference value and capturing an actual value for integration in the central building management system
  • The actual value is based on the nominal volume flow rate such that commissioning and subsequent adjustment are simplified
  • Stand-alone operation or integration in central building management system


  • Static transducer for contaminated air in ventilation and air conditioning systems
  • Modbus commands (Modbus operating mode)
  • External switch contacts/wiring (with analogue interface)

Supply voltage

  • 24 V AC / DC


Integral; slow-running (running time 100 s for 90°)

Installation orientation

  • Not critical


  • Modbus RTU (RS-485) or alternatively analogue signals (0 – 10V or 2 – 10V DC) can be used
  • Interface type set in the factory on the basis of the order code


  • Terminals with rubber cap, therefore no additional terminal box required
  • Double terminal for supply voltage for easy further wiring of up to 3 controllers

Interface information

  • Modbus: including volume flow rate setpoint value and actual value signal, damper blade position, override control
  • Alternatively: volume flow rate setpoint value and actual value signal as analogue signal

Special functions

  • Clearly visible external indicator light for indicating the functions: Set, not set, and power failure
  • Display for actual values, parameter setting and for test functions
  • Activation qvmin, qvmax, closed, open by: Modbus (with Modbus control), external switch contacts (with analogue control)

Parameter setting

  • Parameters specific to VAV terminal unit are set at the factory
  • Operating values: qvmin, qvmax and interface type are set in the factory
  • Subsequent adjustment via display and control element directly on the device or with optional tools: adjustment device, PC software (cable connection in each case), in Modbus mode also via Modbus register access

Factory condition

  • Electronic controller factory-mounted on the terminal unit
  • Factory set parameters
  • Functional test under air; certified with sticker

TVED / 200 / D2 / XS0 / V0 / qvminqvmaxm³/h
1 Type
TVE VAV terminal unit
2 Acoustic cladding

No entry required: none
D with acoustic cladding
3 Material
Galvanised sheet steel (Standard construction)
P1 Powder-coated RAL 7001, silver grey
A2 Stainless steel construction
5 Nominal size [mm]
100, 125, 160, 200, 250
6 Accessories
No entry required: none
D2 Double lip seal both sides
G2 Matching flanges for both ends

7 Attachments (control component)
XS0  Compact controller with static transducer, Modbus RTU, display
8 Operating mode
F Constant value (a setpoint value)
V  variable (setpoint value range)
M Modbus RTU
9 Signal voltage range  (only with operating mode F, V)
0 0 – 10 V DC
2 2 – 10 V DC
10 Operating values for factory setting
Volume flow rates in m³/h or l/s
qvconst  (only with operating mode F)
qvmin  (only with operating mode V, M)
qvmax  (only with operating mode V, M)
11 Volume flow unit

Order example: TVE/100/D2/XS0/M/20-350 m³/h

Acoustic claddingWithout
MaterialGalvanised sheet steel
Nominal size100 mm
AccessoriesDouble lip seal both sides
AttachmentCompact controller Modbus, static transducer
Operating modeModbus RTU
Volume flow rate20 – 350 m³/h


Variants, Product details


Analogue mode 0 – 10 V DC or 2 – 10 V DC (order code, operating mode V, F)

The analogue interface can be adjusted for the signal voltage range 0 – 10 V DC or 2 – 10 V DC. 
The assignment of the volume flow rate setpoint value or actual value to voltage signals is shown in the characteristic curves.

  • The set signal voltage range always applies equally to setpoint value and actual value signals.
  • The signal voltage range is pre-set in the factory according to the order code entries.
  • The signal voltage range can be adjusted by others in the setup menu on the display or using the adjustment device.

Setpoint value default setting

  • In operating mode V (variable mode), the setpoint value defaults with an analogue signal on terminal Y.
  • Setpoint value defaults via the Modbus register 0 are rejected.
  • The selected signal voltage range 0 – 10 V or 2 – 10 V DC is assigned to the volume flow rate range qvmin – qvmax.
  • Volume flow rate range qvmin – qvmax preset at the factory as per the order key data.
  • Subsequent adjustment of qvmin or qvmax is possible in the setup menu on the display or using the adjustment device.


  • In operating mode F (constant value mode), an analogue signal on terminal Y is not required.
  • The volume flow rate constant value qvmin is used.
  • Volume flow rate qvmin is set at the factory as per the order key data.
  • Subsequent adjustment of qvmin is possible in the setup menu on the display or using the adjustment device.


Actual value as feedback for monitoring or tracking control

  • On the terminal U, the actual volume flow rate measured by the controller can be captured as a voltage signal.
  • The selected signal voltage range 0 – 10 V DC or 2 – 10 V DC corresponds to the volume flow rate range 0 – qvnom.
  • In analogue mode (operating mode V, F) there is also the option of querying operating data using the Modbus interface.

Override control

For special operating situations, the volume flow controller can be put in a special operating mode (override control). The following modes are possible: control qvmin, control qvmax, damper blade in the OPEN position or damper blade CLOSED.


Override controls via signal input Y
Thanks to appropriate wiring on the signal input Y, the override controls can be activated according to the connection diagrams via wiring with external switch contacts / relays (see wiring examples). OPEN and CLOSED are only available if the controller is supplied with alternating current (AC).


Override control CLOSED via control signal on signal input Y

  • With signal voltage range 0 – 10 V DC: CLOSED is activated when qvmin= 0 is set and the control signal is Y < 0.3 V DC.
  • With signal voltage range 2 – 10 V DC: CLOSED is activated when control signal is Y < 0.8 V (*1)  DC
    (*1) 0.8V = factory setting


Override controls in analogue mode via Modbus interface

If the Modbus interface is additionally connected in analogue mode, an override control can also be specified via Modbus register 1.

Override control for diagnostic purposes
Activation via the diagnostic menu in the display of the controller or the service tools (adjustment device, PC software).

Prioritisation of various default setting options
Various override control options are prioritised as follows by the controller:

  • Highest priority: defaults via the service connector (adjustment device, PC software) for test purposes
  • Medium priority: defaults via Modbus register 1 or the diagnostic menu on the controller
  • Lowest priority: defaults via the Y signal input of the controller

Product details, Technical data


Compact controllers for VAV terminal units

VAV terminal unitsType of installation component

Part number



Compact controller TR0VM-024T-05I-DS10-MB

Supply voltage (AC)24 V AC ± 20%, 50/60 Hz
Supply voltage (DC)24 V DC ± 20 %
Power rating (AC)NW 100 – 200: max. 4 VA
NW 250 – 400: max. 7 VA
Power rating (DC)NW 100 – 200: max. 2.5 W
NW 250 – 400: max. 4 W
Power consumption (when running/when idle)

1 W

Run time for 90°100 s
Setpoint value signal input (analogue optional)0 – 10 V DC, Ra > 100 kΩ
or 2 - 10V DC Ra> 50 kΩ
Actual value signal output0 – 10 V DC or 2 – 10 V DC; max. 5mA
IEC protection classIII (protective extra-low voltage)
Protection levelIP 42 (with the terminal cover attached)
EC conformityEMC to 2014/30/EU
Bus connectionModbus RTU, RS485
Number of nodes128
Adjustable communication parameters1200 – 115,200 Bd
Start bit: 1
Data bits: 8
Stop bits: 1 or 2
Parity: None, Even, Odd
Setpoint / actual value interface (Modbus)via Modbus register list
Cable terminationExternally required

Interface configuration of control component

Depending on the setting, the Modbus communication interface or the analogue interface is available for defaulting the volume flow rate setpoint. The so-called interface mode is preset at the factory according to the order code and can be adjusted on-site by setting via the menu navigation or the Modbus registers.

Typical interface configuration


Setpoint value default setting via:Actual values via:Corresponds to order key optionMenu configuration (Mode)
Analogue operationAnalogue 0 – 10 VAnalogue 0 – 10 VV or FCA0
Analogue operationAnalogue 2 – 10 VAnalogue 2 – 10 VV or FCA2
Modbus operationModbus register setpointModbus register actual value or analogue 2 - 10VMCB

A special configuration of the Modbus register interface mode enables the configuration of a mixture of Modbus and analogue modes. For more information, see the description of the interface mode in Modbus register 122.


Supplementary use of the Modbus interface in analogue mode

In analogue mode, only the setpoint values defaulting on the analogue input are used. Setpoint default setting via the Modbus interface (register 0) is not possible. Any write attempts will generate an error. Regardless of the selected interface configuration, however, the other Modbus registers can be used. In this way, the volume flow rate actual value and blade position operating values can be read out from a higher-order central BMS with local control via an analogue signal and a connected Modbus, or central override control can also be triggered.

Communication interface Modbus RTU (operating mode M)


MeaningAccess rightStorage
Volume flow rate setpoint value [%]
Reference: Vmin – Vmax (qvmin – qvmax)
Resolution: 0 – 10000
Volume flow rate setpoint value: 0.00 – 100.00%
1Activation of an override control; 0 = None; 1 = Open; 2 = Close; 3 = Vmin; 4 = VmaxR, WRAM
2Command triggering 0 = none; 1 = adaptation; 2 = test run; 4 = controller resetR, WRAM
4Current damper blade position [%]
Resolution: 0 – 10000
Damper blade position: 0.00 – 100.00%
5Current damper blade position [°]
Reference: without decimal places
6Current actual volume flow rate [%]
Resolution: Vnom
Resolution: 0 – 10000
Volume flow rate actual value: 0.00 – 100.00%
7Actual volume flow rate in volume flow unit [m³/h], [l/s], [cfm] acc. Register 201RRAM
8Voltage at analogue input Y [mV]RRAM
103Firmware version



104Status information
(Bit = 1 active, bit = 0 inactive)
Bit 5 mechanical overload
Bit 8 internal activity e.g. test run, adaptation
Bit 10 bus timeout monitoring triggered
105Operating range limitation: Operating parameter Vmin (qvmin) [%]
Resolution: Vnom
Resolution: 0 – 10000
Vmin: 0.00 – 100.00%
106Operating range limitation: Operating parameter Vmax (qvmax) [%]
Resolution: Vnom
Resolution: 0 – 10000
Vmax: 0.00 – 100.00%
108Behaviour in case of bus timeout; 0 = none; 1 = close; 2 = open; 3 = qvmin; 5 = qVmaxR, WEEPROM
109Definition of bus timeout [s]R, WEEPROM
120Definition of operating range: operating parameter Vmin (qvmin) in volume flow unit [m³/h], [l/s], [cfm] acc. register 201R, WEEPROM
121Definition of operating range: operating parameters Vmax (qvmax) in volume flow unit [m³/h], [l/s], [cfm] acc. Register 201R, WEEPROM
122Interface definition (Interface mode) For assignment see separate tableR, WEEPROM

130 *

Modbus address (device address)R, WEEPROM
201Volume flow unit 0 = l/s; 1 = m³/h; 6 = cfmR, WEEPROM
231Setting of mode:
Bit 0 defines the characteristic of the analogue interface.
Bit 0 = 0 characteristic: 0 – 10 V
Bit 0 = 1 characteristic: 2 – 10 V
Bit 4 defines the actual value signal as volume flow rate actual value or damper blade position.
Bit 4 = 0 volume flow rate actual value
Bit 4 = 1 Damper blade position
All other bits must not be changed.

Modbus parameter set communication settings: baud rate, parity, stop bits, assignment see separate table

569Modbus communication settings: Modbus Response Time = 10 ms + delay; with delay= 3 ms × register value 0 – 255R, WEEPROM
572Setting of switching threshold for override control CLOSE via control signal for signal voltage range 2 – 10 V:
Setting range 0.5 V – 1.8 V
Default value 0.8V (register value = 20)
Resolution: 1 setting unit = 40mV

* Factory setting: Modbus address 1
R = Register can be read
R,W = Register can be read and written
RAM = Volatile register value
EEPROM = Register value not volatile, but saved permanently (max. 1 million write processes)

Detailed information on register 122 (communication interface setpoint/actual value - Interface Mode)

Register value

Signal inputFeedback signal
Analogue (0) 2 – 10 V(0)2 – 10 V
1Modbus via Register 0(0)2 – 10 V
2Modbus via Register 0Register 10
3Analogue (0) 2 – 10 VRegister 10

Detailed information on register 568 (Modbus communication parameters)

Register value

Display setting valueBaud rateParityStop bits

15 **






** Factory setting: Modbus communication parameters

Range of display functions

Display functions

  • Volume flow rate actual value (unit optionally m³/h, l/s, cfm)
  • 3-character display with positional notation
  • Status and error display for various operating states, including display of activated override control, display of diagnostic function

Parameter setting

  • Adjustment option for the unit of the volume flow rate display m³/h, l/s, cfm
  • Adjustment option for the operating range qvmin, qvmax
  • Selection of the interface configuration Modbus or analogue including signal voltage range 0 – 10 V or 2 – 10 V DC
  • Adjustment option for Modbus communication settings (address, baud rate, stop bits, parity)


  • Activation of a test run
  • Activation of override controls Open, Closed, qvmin, qvmax, motor stop (note prioritisation)
  • Display of the voltage value on the analogue input

Note on static transducer type used

  • Installation orientation not critical
  • Zero point correction not required

After installation, wiring and connection of the supply voltage

  • When using the Modbus interface: set the Modbus communication parameters via the integral menu, the air terminal unit is then ready
  • Setpoint value default setting via Modbus register
  • When using the analogue interface: air terminal unit is immediately ready for use
  • Comply with volume flow rate control range from 4 – 100 % of qvnenn; do not set a volume flow rate which is below the minimum flow rate of the control unit
  • Only briefly remove the protective cap for the terminals during wiring

Use and description of the display

Pressing the LED push button (< 3 s) selects the next menu item ① - ⑥. The selected menu item can be changed by pressing the LED push button for more than 3 s. Changing is done with the rotary selector switch. Pressing the LED push button again (< 3 s) confirms the selected value. If no entry is made for >= 60 s, the system returns to menu item 1.

Table 1: Description of the menu items

① FlowDisplay of actual values or operating states. Setting the volume flow rate unit m³/h, l/s, cfm.
② VminSetting qvmin
③ VmaxSetting qvmax


Displays the control signal and feedback signal alternately in [V],
Activation of override controls for test and diagnostic purposes:
tst = test run
oP = damper OPEN
cL = damper CLOSE
Lo = qvmin
Hi = qvmax
St = Motor stop
oFF = Override control Off
000 = Display firmware version


Selection of the operating mode:
CA0 = Setpoint value setting and actual value return via analogue interface (0 – 10 V)
CA2 = Setpoint value setting and actual value return via analogue interface (2 – 10 V)
CB2 = Setpoint value setting and actual value return via Modbus - Optional actual value return via (2 – 10 V)


Setting the modbus address: 1 - 247

and the baud rate, parity, stop bits: 1 (b1) - 32 (b32)

Description of status LEDs and error messages

LED flashing signalStatusDisplay
No supply voltage connected.

Inform TROX service technicians

Actuator overload detected (block)

Synchronisation after Power Up

Test mode activated

Overpressure sensor (overpressure)

Setpoint value or override control position not yet reached (display changes between e.g. Hi = High and actual value)

Override control position reached (display changes between e.g. Hi = High and actual value)

Normal operation with the setpoint being maintained. Signalled as long as the actuator does not rotate to readjust the setpoint value.

The flashing signal appears every 2 seconds. 1 = LED is illuminated, 0 = LED is not illuminated


product information


operation manuals

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