1735 Water Vapour Transmitter

1735 Water Vapour Transmitter

In-situ Water Vapour Analysis in High Humidity Applications

Moisture measurement improves product quality and consistency and reduces fuel costs for drying and baking processes.

Novatech has enhanced its range of analysers by adding the 1735 Water Vapour Transmitter and the 1231HWV High Water Vapour Oxygen Probe


The 1735 transmitter uses the measure of oxygen to calculate the level of water vapour by using the difference between the wet oxygen reading and the dry oxygen reading.

The Novatech zirconia probes incorporate the world’s most rugged zirconia sensors. Now there is a Novatech oxygen probe designed especially for baking and drying ovens.
Used with the 1735 water vapour transmitter, the 1231HWV oxygen probe is capable of reading the oxygen concentration in atmospheres with up to 99.99% water vapour and at temperatures up to 600°C (1,100°F).

The 1735 / 1231HWV water vapour analysis provides rapid payback for processes such as:

  • Drying ovens
  • Baking ovens
  • Paper drying hoods
  • Gypsum and plasterboard dryers
  • Timber drying kilns

The 1735 / 1231HWV water vapour analysis can provide accurate moisture control in atmospheres up to 600°C

Easy to operate, reliable and no regular calibration needed. Select the unit of measure to display and output from:

  • Water Vapour %
  • Dew Point
  • Mixing Ratio
  • Specific Humidity
  • Relative Humidity
  • Absolute Humidity
  • Oxygen

Fast, Accurate and Reliable

The oxygen sensor, which measures water vapour due to oxygen displacement in the oven atmosphere, provides accurate and virtually drift-free measurement for years.
Highly responsive, eg: typically 3 seconds for indirect heated applications.

Controlling humidity

The 1735 / 1231HWV can be used with controllers, including PLC’s, to provide accurate continuous control of the moisture level.

Direct Fired Processes

The 1735 / 1231HWV measures the “wet” oxygen level of the process using an in situ zirconia oxygen probe and can accept a remote signal input (4-20mA) proportional to the dry oxygen level to then calculate the percent water vapour in the process. If this signal is not available from an existing CEMS installation then the 1735 can be supplied with a reference gas sensor as a simple sampling system to determine the “dry” oxygen level in the process.

The 1231HWV oxygen probe and the 1735 transmitter is designed in Australia and manufactured in the Melbourne factory. The sensor embodies the research and development of Australia’s premier research organisation, CSIRO.

The probe can be inserted directly into the oven / dryer therefore eliminating the need for a high-maintenance sampling system.

Specifications – 1735 Transmitter


  • Two zirconia oxygen probes or sensors or
  • One zirconia sensor & auxiliary thermocouple type J, K, R or S
  • Burner “On” signal (dry contact)
  • Purge air flow switch


  • Four programmable alarm relays
  • Two isolated 4-20mA or 0-20mA
  • SSR outputs to purge & calibration check gas solenoid valves

Range of Outputs

  • Water Vapour %:
  • 0 to 100%
  • Dew Point:
  • -50 to 100°C
  • Mixing Ratio:
  • 0 to 10,000 g/Kg
  • Specific Humidity:
  • 0 to 1,000 g/Kg
  • Dryer Temperature:
  • 0 to 400°C
  • Relative Humidity:
  • 0 to 100%
  • Absolute Humidity:
  • 0 to 1,000 g/m³
  • Oxygen:
  • 0 to 25%


  • Common alarm relay with 20 user selectable instrument alarm functions
  • Three programmable process alarm relays
    • Water Vapour Low/High
    • Dew Point Low/High
    • Mixing Ratio Low/High
    • Specific Humidity Low/High
    • Oxygen Low/High
    • Probe Temperature Low
    • Purge in Progress
    • Cal Check in Progress
    • Any alarm condition not selected for the common alarm
  • Four separate alarm thresholds can be set for calculated process variables
  • Multiple selections can be made for all relays

Alarm Contacts

  • Normally open failsafe (open for alarm state)
  • 240VAC / 30VDC, 2A

Range of Local Indication

  • Water Vapour %0 to 100%
  • Dew Point-50 to 100°C
  • Oxygen0 to 100%
  • Mixing Ratio0 to 10,000g/Kg
  • Specific Humidity0 to 1,000g/Kg

Network Interface

  • RS-485 MODBUS™

Secondary Parameter Display

  • Probe Thermocouple Temperature
  • Probe EMF
  • Probe Impedance
  • Probe Oxygen %
  • Zone 1 & 2 Water Vapour %
  • Zone 1 & 2 Dew Point
  • Zone 1 & 2 Mixing Ratio
  • Zone 1 & 2 Specific Humidity
  • Dryer Temperature
  • Relative Humidity
  • Absolute Humidity
  • Ambient Temperature
  • RGS Temperature
  • Ambient RH%
  • External Dry Oxygen
  • Runtime
  • Service Date
  • 4-20mA Output 1
  • 4-20mA Output 2

Options available will vary depending on device configuration


  • ± 1% of the actual oxygen reading with a repeatability of 0.5%. For example, at 2% oxygen the accuracy would be ±0.02% oxygen.
  • Contact Novatech for specific applications for other measured process variables

Environmental Rating

  • Operating Temperature -25°C to 55°C
  • Relative Humidity 5% to 95% (non-condensing)
  • Altitude 2000m Maximum

Power Requirements

  • Mains Voltage 100 to 240VAC -6/+10%, 50/60Hz
  • Overvoltage Category II (IEC60364-4-443)
  • Requires 5W for controller plus probe power

Degree of Protection

  • IP65
  • IP54 with internal reference air pump


  • 315mm W x 190mm H x 110mm D


  • 3.3kg (7.3lb)

Specifications – 1231HWV Probe

Model 1231HWV
Applications High moisture atmospheres up to 600°C
Probe Insertion Length 250, 350, 500, 750, 1000mm
Process Connection 1.5″ BSPT or NPT
Outer Sheath 32mm OD 316 Stainless Steel with 42mm filter
Electrical Connection Supplied with weatherproof connector and cable specified length up to 50m
Heater Yes
Internal Thermocouple Type ‘K’
Response Time Typically <4 seconds
Head Temperature 100°C Max
Reference Air Connection 1/4” tube
Gas flow <50cc/min
Particulate Filter 30µm sintered titanium alloy
Weight 2.1Kg + 160g per 100mm insertion length
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