W&T connects
Interfaces for TCP/IP, Ethernet, RS-232, RS-485, USB, 20mA, glass and plastic fiber optic cable, http, SNMP, OPC, Modbus TCP, I/O digital, I/O analog, ISA, PCI
Data sheet:

Web-Graph Air Quality

  • Web-Graph Air Quality

Monitor temperatures, relative humidity and air quality

On-demand ventilation control in office buildings, schools, education and centers and sports facilities often involve measurement of CO2. But a drawback of CO2 measurement is that odors caused by VOC are not detected, since they have only a slight effect on the CO2 measurements.
Even though there is an actual ventilation need, this condition is not detected using traditional technology. With this VOC measuring instrument the room air quality can be determined based on human perception.

More information on VOC can be found here



  • Temperature sensor:
    • Measuring range: 0°C...50°C
  • Relative humidity sensor:
    • Measuring range 5..95% RH, permissible ambient 0..95% (non-condensing)
  • Air quality sensor:
    • Measuring range 450..2000ppm VOC as CO2 equivalent


  • Configurable LED tower on sensor for optical indication of limit values
  • Monitor temperatures and trends from a browser
  • Alarm and reporting function:
    • E-mail for alarm or reporting functions
    • SNMP polling / alarm traps
    • Up to 8 alarm messages can be configured
  • Dynamic integration into other Web sites:
    • Direct access to current measurement values via AJAX, JavaScript and Java applet
  • Additional software interfaces for incorporating into your systems/databases:
    • OPC server
    • Syslog
    • Sensobase (database integration via ODBC)
    • TCP and UDP sockets, client and server
    • FTP (data logging)
  • Possible applications:
    • Monitor temperatures in the server room, network cabinet or office
    • Direct display of multiple measuring points in the browser via Java applet
    • Logging of measurements via FTP, Excel file, email attachment and internal memory
    • Dewpoint measurement, climate monitoring
    • Green IT: Monitor efficiency of the server room climate control

Data logger:

  • Internal data logger
    • Memory size: min. 10 weeks, max. 8 years
    • Save frequency: 1, 5, 15, 60 min
  • Document measurement data online in the W&T Cloud and access from anywhere in the world
  • Internal clock
    • Time synchronization via time server calibration

Standards & more

  • Supply voltage via Power-over-Ethernet (PoE)
    • Phantom power using data pairs
    • Power over unused wire pairs
    • External power supply is an alternative
  • Conforms to standards both in office and industrial environments:
    • High noise resistance per EN 61000-6-2
    • Low noise emission per EN 55032:2015 + A1 Cl. B, EN 61000-3-2 & EN 61000-3-3
  • 5 year guarantee

Technical data

Connections and displays:

  • Combined sensor:
    • Temperature, relative humidity, air quality measurement
    • DB9 receptacle
    • Cable length: 2m (can be extended to max. 20m)
  • Network:
  • Electrical isolation:
    • Measurement inputs to network: min. 500 volts
  • Power supply:
    • Power-over-Ethernet (PoE) or via screw terminal with
    • DC 18V .. 48V (+/-10%) or AC 18Veff .. 30Veff (+/-10%)
  • Current consumption:
    • AVG: 80mA @24VDC, 100mA @20VAC
    • Max: 90mA @24VDC, 50mA @48VDC
    • PoE Class 1 (0.44 - 3.84W)
  • Displays:
    • 1 LED Power
    • 4 LEDs Status and Error
    • 3 LEDs traffic-light display in sensor

Measuring unit:

  • Measuring range:
    • 0°C...50°C, 5..95% RH, 450-2000ppm VOC as CO2 equivalent
  • Resolution:
    • 1/10 °C, 1/10% rH

  • VOC sensor, detected substances:

    • Substance class Occurrence/use (example)
      Aldehydes Disinfectants, paints, varnishes, tabacco smoke, perspiration, transpiration
      Aliphatic hydrocarbons Gasoline and diesel engine fuels, vehicle exhaust, LPG, solvents, cosmetics, flatulence, household materials, PVC
      Alcohols Coating agents, household materials, adhesives, solvents, carpets, disinfectants, cosmetics
      Amines Dyestuffs, agricultural and pharmaceutical chemicals
      Aromatic hydrocarbons Printers/copiers, computers, solvents, PVC, gasoline and diesel engine fuels, tobacco smoke
      Ketones Solvents, coating agents, adhesives, fingernail polish removers, paints, varnishes, carpets

  • Measuring error:

    • Temperature:
    • typ. @ 25°C ±0.3°C
    • max. @ 0..50°C ±1.2°C

    • Relative humidity:
    • typ. @ 25°C ±3%rH
    • max. @ 0..50°C ±7%rH (0-100%rH)
    • Long-term stability typ. <0.5%rH / year

  • Aging of the VOC sensor:

    • Aging of the sensor is internally compensated for. It is however recommended that a CO2 comparison measurement be performed once a year.
  • Measuring frequency:
    • 4s
  • Storage frequency:
    • 1, 5, 15, 60 min
  • Memory depth (832kB):
    • min. 10 weeks, max. 8 years
  • Deviation of the internal clock:
    • max. 4.32 min. / month (without time server calibration)
    • max. 3 sec. (with time server calibration)

Housing and other data:

  • E-mail function:
    • Mail for sending alarms or as reporting function
  • Housing:
    • Plastic compact housing, 105x75x22mm
  • Weight:
    • approx. 200g
  • Ambient storage temperature:
    • -25..+50°C
  • Ambient operating temperature:
    • 0..+50°C
  • Permissible relative humidity:
    • 0..95% RH (non-condensing)
  • Scope of delivery:
    • 1x Web-Graph Air Quality for DIN rail mount
    • 1x W&T prober, 2m (temperature/relative humidity & VOC)
    • 1x product CD with WuTility management tool, OPC server, SNMP-MIB, reference manual German/English