Temperature and Humidity is essential in a multitude of applications, such as:

  • Monitoring of concrete setting in construction projects
  • Monitoring building moisture levels following escape of water damage or flooding to ensure restoration is safe to start
  • Monitoring conditions in mould prone dwellings to identify root causes and safeguard occupants health
  • Providing links to Building Management Systems
  • Monitoring and managing environments for agriculture and horticulture
  • embedding technology to monitor in-situ critical health service equipment, data centres, broadcast equipment, pest control equipment as well as food and beverage dispensing equipment
  • This list describes a range of differing applications but is not an exhaustive list of application in which temperature and humidity monitoring is necessary


There are three main measurements of humidity:

  • Absolute humidity is the water content of air
  • Relative humidity [RH]  expressed as a percent, measures the current absolute humidity relative to the maximum for that temperature
  • Specific humidity is a ratio of the water vapour content of the mixture to the total air content on a mass basis
  • See Wikipedia for more information


Our customers are mostly interested in RH readings and often “in situ” (which means within specially created cavities in building materials, or air flows of drying equipment), so we have developed a range of custom sensors specifically for those applications, and this includes the award winning HygroBug.


Combined Temperature and Relative Humidity

Regardless of the application area Relative Humidity (RH) and temperature almost always go hand in hand as RH without temperature is almost meaningless. For a given amount of moisture in a set amount of air, the RH value will reduce as temperature increases, because hot air is capable of carrying a larger amount of water. This movement of RH with temperature is one of the many important reasons why it is important to record and display graphically the RH and temperature over time with monitoring systems, and not just take sporadic isolated data points on their own

DBK DRying Data Slide

The graph above demonstrates data taken from the HygroNet. The HygroNet was chosen as the system of choice for use by the BDMA in seminars and test comparisons.



Specific Humidity and Mixing Ratio are derived values from RH and temperature that are calculated on line, in real time on the CDLSmarthub so it can also be displayed graphically per sensor location along with all the other parameters, and have high and low alarms thresholds set for alarm notifications.

Case Study tab - Westminster Hall

900 year old Westminster Hall to be installed with 21st century remote monitoring systems

Caption Data will be supplying a number of battery powered wireless sensors, that will be installed throughout the structure of the hammer beam roof.

The magnificent hammer-beam roof of Westminster Hall is the largest medieval timber roof in Northern Europe. Measuring 21m by 73m (68ft by 240ft) and some 30m tall, the roof was commissioned in 1393 by Richard II, and is still standing.

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Pengersick Castle

Environmental monitoring at notoriously haunted castle in Cornwall

Caption Data were recently commissioned to install an environmental monitoring system at a notoriously haunted castle in Cornwall.

Pengersick Castle is undergoing a significant renovation program to return the Grade One listed building back to its former, impressive state.

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Case Study tab - HygroBug In Situ

How can the HygroBug™ help monitor drying of damp concrete?

Some of the problems of monitoring the drying of concrete are:

  • Drying from surface can mislead as to in depth humidity if measurements are done at the surface, or …
  • … Equalisation period is too long, and …
  • … salts and impurities can distort results.


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Case Study tab - Thank god for HygroNet

Thank God for the HygroNet

“Thank God for Hygronet!” says Borge Enga one of Polygon AS [Norway] Project Managers.

Borge explained further details in a recent conference call with CDL, the makers of HygroNet™. The story began with an instruction for Polygon to deal with water damage in a rather unusual property – a house of some 180m2. The house not only had many rooms with many different construction techniques, but it had valuable wooden ceiling panels that were to be protected at all costs!


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Case Study tab - Slim temp & RH Probe

Slim Temperature & RH probe for forced air drying systems

As the use of forced air drying systems is becoming more widespread there is a need to be able to monitor the progress of drying, real time.

Depending on the method used quite often there is a need to measure within pipe/ductwork and generally it is impractical to place a whole sensor into the air flow. This can be down to the fact it is physically not practical or the temperature within the pipe work is simply too high.


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Introducing the RDL//1000

The RDL//1000 easily connects up to 256 sensors with a 500m line of sight range, and is ideally designed for applications in structural and environmental monitoring

RDL//1000 temperature and humidity monitoring system for environmental monitoring for Specifications

  • Parameters measured: ambient temperature and humidity, WME, plus more with external sensors connected via digital inputs. Sensors are interchangeable.
  • Up to 500m line of sight sensor range
  • Total system range (Diameter) 1000m – can be further increased with repeaters
  • Battery powered sensors
  • Fully roaming SIM


More information


Introducing the HygroNet

HygroNet remote data logging systems are designed to support the water damage restoration industry by measuring key data throughout the drying cycle

Hardware Tab - HygroNet

  • Parameters measured: ambient temperature, ambient humidity, surface temperature, in wall temperature, in wall humidity and WME
  • Calculated parameters: Specific humidity and dew point
  • Logging interval: 1 sec to 24 hours


More information


Types of sensors


Works by measuring the change in electrical capacitance of a polymeric “sandwich material”

This type of digital sensor is very widely used in a myriad of devices in automotive, industrial &  consumer electronics applications, with literally billions of sensors produced.

We use the industry leading Swiss company Sensirion’s SHT21 [link to data sheet] which offers a small footprint of 3mm, viable RH & T accuracy across a useful range&  is pre calibrated.

Limitations can be experienced around prolonged exposure at very high RH levels when upward drifting of results is experienced. Also the “drying out” process following such exposure can be cumbersome.



GE* HygroStick

An Alternative to the Capacitative sensor type is the Resistive sensor.

GE developed their market leading HygroStick product for measuring humidities in building materials using this technology, and have licenced Caption Data to integrate these sensors into their Remote Monitoring Systems, particularly useful for Construction, Damage Restoration, Flooring, and other industries where prolonged exposure to high humidities happens.

*The Sensors division of GE was sold to Amphenol in 2013

These sensors can be used immediately and seamlessly with the RDL//1000 system from CDL, offering the following advantages:

High stability at high RH values over extended time periods – no appreciable drift over time

High accuracy +/- 1.75% RH [cf +/-  >4-5% for Capacitative type at high RH]

Built in Unique ID calibration data, retrieved and used by the CDL system


Wood Moisture & WME


The varying electrical resistance of wood depending on its moisture content has been known for over a century, and forms the basis of the Hygrobug. Rather than inserting probes into the wet building material a hole is drilled and a Hygrobug inserted. This standardised wooden dowel equalises to the humidity of the ost material and the electrical resistance  is measured via any Hygronet or RDL//1000 wireless sensor. The advantages compared to a capacitative type sensor are the speed of response and resolution of measurements to quickly detect the impact of drying regimes within the host material.  The Hygrobug overcomes the various problems of using electrical probes for long term monitoring

The HygroBug recently received an award for innovation of the year at the BDMA 2013 annual award conference.

Electrical probes

All CDL systems have a standard 3.5mm jack plug socket and will accept data form proprietary electrical resistance probes. Our hardware and firmware offers resolution down to 13% WME values



All CDL sensors are supplied with our own or the sensor manufacturers  standard calibration.

The RDL//1000 and Hygrostick systems offer a unique calibration management system, with visibility down to individual sensor level within a monitoring system

Actually it’s not software! It’s SaaS, Software as a Service. We host all the software on our super secure servers (see more on security), and provide you with real time access to data in graphical format via the CDLSmartHub, which is completely web based and means there is no need to install software – making the CDLSmartHub accessible from any device, anywhere, at anytime.

CDLSmartHub Tab

Features and Benefits

  • Accessible online via the CDLSmarthub
  • No need to download / install software
  • Auditable trail of data for due diligence
  • User friendly interface
  • Initial and ongoing support
  • Multi-tiered user access levels
  • Remote management of system configurations


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