A customer required a solution for monitoring very low, bidirectional pressures of waste gas within a highly hazardous industrial environment. The key challenges involved not only the measurement of a tight pressure range close to atmospheric but also meeting exceptionally stringent ATEX intrinsic safety standards for areas where highly flammable gases are continuously present. A portable, battery-operated device with data logging functionality was essential for their process monitoring and analysis. The proposed solution was a high-precision digital pressure gauge with an interchangeable sensor module specifically configured for the application.
- Application: Waste gas pressure monitoring
- Challenge: Measuring low bidirectional pressure, from -50 to +50 mbar.
- Environment: ATEX Zone 0/1 hazardous area with IIC gas group.
- Requirement: Portable, battery-powered pressure data logger.
A client involved in industrial process applications presented a challenging requirement for a pressure measuring instrument. The application involved the monitoring of waste gas, where precise pressure measurement is critical for safety and process efficiency. The pressure range was very low and bidirectional, specified as -50 to +50 mbar. This type of measurement is often associated with monitoring flue draft in stacks, ventilation systems, or pressure inside sealed process vessels like biogas digesters, where pressures fluctuate slightly above and below the ambient atmospheric pressure. Accurately capturing these small deviations is vital for maintaining stable process conditions and ensuring proper flow.
The most critical aspect of the application was the hazardous nature of the environment. The customer specified a requirement for an ATEX-certified instrument suitable for areas where the wetted parts would be exposed to a Zone 0 environment and the external housing to a Zone 1 environment. Furthermore, the certification needed to cover Gas Group IIC, which is the most stringent classification and includes highly flammable and explosive gases such as hydrogen and acetylene. This indicates the waste gas medium could have a variable and potentially highly volatile composition, demanding the highest level of intrinsic safety to prevent any risk of ignition from the measurement device. The need for a pressure datalogger also made it clear that the ability to record pressure trends over time was a mandatory feature, likely for process analysis, troubleshooting, or compliance reporting.
To meet these demanding requirements, the DM01 series precision digital gauge was proposed. This instrument features an innovative modular sensor concept, where the digital display unit is separate from the interchangeable pressure transmitter module. This allows for exceptional versatility, as a single display unit can be paired with multiple sensor modules to cover different pressure ranges or applications. For this specific case, a specialised intrinsically safe version of the display unit, certified for Zone 0 use, was selected. This particular model is distinguished by a conductive front foil, a design feature necessary to meet the stringent II 1G Ex ia IIC T4 Ga rating, ensuring it was safe for the specified environment.
The accompanying sensor module was configured with a custom bidirectional pressure range of -50 to +50 mbar and a high accuracy of 0.125% of full scale. This level of precision is essential for detecting minor fluctuations in low-pressure systems. The wetted parts, including the pressure port and diaphragm, are constructed from stainless steel grades 1.4404 and 1.4435, with FKM seals providing excellent chemical resistance suitable for direct contact with corrosive waste gas.
The integrated data logger was a key feature that directly addressed the customer’s request. The DM01 can store over 600,000 pressure and temperature readings, which can be recorded cyclically or linearly at user-defined intervals. This data can then be downloaded to a PC via a USB interface cable for analysis using the provided software, enabling the creation of detailed measurement reports. As a battery-powered device, the instrument offers over 2,000 hours of standard use, making it ideal for portable use in field diagnostics, temporary process monitoring, or as a calibration reference tool in locations where line power is unavailable or impractical. The large graphic display, complete with a 100-segment bargraph and background illumination, ensures that readings can be clearly seen in all conditions.
DM 01 Pressure Data Logger
- Part No: DM01-A2G / DM01-M0K-S050-E-B2-100-1-000 / ZUSBCD01
- Pressure Sensor Modules: -50 to +50 mbar gauge
- Accuracy: 0.125% FS
- Process Connection: G1/2 DIN3852 male
- Data Storage Type: Data Logging – DM01
- Digital Interface: USB Converter and PC Software
- Optional Extras: ATEX intrinsically safe approved (zone 0)