IN Brief:
- LDH313 measures pressure dew point from −20°C to +20°C, with specified accuracy of ±2°C and repeatability of ±1°C.
- IO-Link 1.1 and a configurable 4–20mA output allow integration into digital or analogue monitoring systems.
- The sensor is rated for process pressures up to 50 bar, with IP68/IP69 protection and a replaceable filter.
ifm electronic has introduced the LDH313 dew-point sensor to UK industrial users for monitoring moisture in compressed-air and non-corrosive gas systems. The compact instrument measures pressure dew point from −20°C to +20°C and medium temperature from −20°C to +60°C, with IO-Link communication and a configurable 4–20mA analogue output.
The unit is rated for process pressures up to 50 bar and uses a G½ threaded connection. Its sensing element applies a capacitive measurement principle, while a replaceable filter protects the measurement assembly and provides a maintenance route without replacing the entire instrument.
Pressure dew point is the temperature at which water vapour begins to condense from gas at its existing pressure. The distinction from atmospheric-pressure dew point is important because a gas’s moisture saturation conditions change with pressure. Measuring at the operating pressure allows the air-quality condition to be assessed within the compressed-air network.
Condensate can cause corrosion in distribution pipework, affect valves and other pneumatic components, and introduce unwanted water into production processes. In applications such as precision manufacturing, coatings and food handling, the acceptable moisture content may be governed by particular product or equipment requirements rather than by a single universal threshold.
The LDH313’s specified pressure-dew-point measurement range is −20°C to +20°C, with accuracy of ±2°C and repeatability of ±1°C within that range. Its display-value range extends to +60°C, but that wider indication must not be presented as the accuracy-qualified dew-point measurement span.
Separate medium-temperature measurement covers −20°C to +60°C, with stated accuracy of ±1K. The two process values can be transmitted digitally through IO-Link, allowing supervisory systems to assess the moisture condition alongside the temperature of the compressed gas.
The sensor uses IO-Link revision 1.1 with a class A master port and provides a scalable 4–20mA output that can be assigned to pressure dew point or temperature. It is not specified as a device with a separate configurable switching output, contrary to some abbreviated product descriptions.
Through IO-Link, the instrument can be configured remotely and its parameter set backed up for restoration when a compatible device is replaced. Digital transmission also avoids conversion of the transmitted process values into an analogue signal before they reach the IO-Link master, although correct installation and controller configuration are still required.
The manufacturer’s response times differ depending on whether the gas becomes wetter or drier. Under the specified test transitions, the T90 response is below 20 seconds from dry to humid conditions and below 120 seconds from humid to dry. These values describe a defined change in the test medium, not a guaranteed alarm delay under every operating condition.
The different response characteristics can influence how a control system interprets trends. A fast rise in pressure dew point may signal worsening drying performance, while a subsequent improvement may take longer to appear in the sensor output. Filtering, the flow arrangement and the configured monitoring interval can add further effects at system level.
The device is supplied in a stainless-steel tubular housing approximately 30.1mm in diameter and 119.1mm long, with a four-pin M12 electrical connector. ifm specifies an 18–30V DC supply, a medium temperature range of −20°C to +60°C and protection ratings of IP68 and IP69 under defined conditions.
Those enclosure ratings describe resistance to specified external environmental exposure. They do not by themselves establish chemical compatibility with every process gas or suitability for every compressed-air installation; the manufacturer limits the stated application to compressed air and non-corrosive gases.
Continuous dew-point monitoring can support control of air dryers and detection of deteriorating air quality before moisture reaches sensitive equipment. A dryer-control system may use the value to adjust operation according to the required air quality, but the sensor does not dry the air or directly measure the electrical energy consumed by the dryer.
The attainable energy reduction, if any, depends on the drying technology, air demand, operating pressure and control strategy. A sufficiently dry reading alone does not prove that a dryer is operating efficiently, and lowering the dew-point setpoint unnecessarily may increase energy consumption.
ifm also provides monitoring equipment for pressure, air consumption and leaks. Combining these measurements can help operators distinguish moisture-related problems from changes in consumption or network pressure, provided the instruments are installed at representative positions and their readings are interpreted against the system’s operating conditions.
The LDH313 provides a defined moisture measurement and two communications options for integration into existing control environments. Selection and commissioning still require checking the intended dew-point range, response behaviour, compressed-air quality requirements and the compatibility of the installation with the sensor’s mechanical and electrical specifications.
