Differential pressure sensors for failsafe applications

Paul Boughton

Sensirion is launching new versions of its SDP600 series differential pressure sensors that are able to perform certified failsafe measurements. The digital SDP600 differential pressure sensors are already used successfully in medical and HVAC applications and feature excellent long-term stability as well as high sensitivity and accuracy, especially at very low pressure differences. The new models - namely the SDP620, SDP621, SDP630 and SDP631 - now additionally allow verification of the measured values. Thanks to their pre-certification, the sensors can be easily integrated into failsafe control systems, which is particularly relevant for applications with high safety requirements, such as gas burners.
The new types of differential pressure sensors can be configured to provide special test patterns for error checking by an external microprocessor. This makes it possible for the sensors to achieve measurement of differential pressure and mass flow values to Class C safety level, provided that the test patterns are executed properly. Specifically, the SDP620, SDP621, SDP630 and SDP631 comply with Euronorms EN 12067-2:2004, 'Gas/air ratio controls for gas burners and gas burning appliances - Part 2: Electronic types' and EN 13611:2007, 'Safety and control devices for gas burners and gas burning appliances - General requirements.'
Sensirion says the new models are tailored to different hardware designs and measurement applications to allow customers a high level of flexibility when integrating. While the mass flow temperature compensated SDP621 and SDP631 are optimally suited for measuring mass flow, the SDP620 and SDP630 sensors output the true differential pressure value. Furthermore, the SDP620 and SDP621 sensors are intended for a direct threaded connection to a pressure manifold with O-ring sealing, while the SDP63x models are equipped with standard hose connectors. The new versions can, for example, be integrated into safety-relevant combustion control systems with electronic air/gas ratio control. Because of their failsafe certification, it is not necessary to use two redundant sensors to meet high safety requirements. This permits a cost-effective design and, thanks to the outstanding performance of the sensors, the turn-down ratio of gas burners can be boosted to more than 1:10 to provide energy-efficient and environmentally-friendly combustion.
For more information, visit www.sensirion.com