A manufacturer of low-power IoT data loggers needed a pressure sensor solution for a new water utility monitoring system. The application involved measuring pressure differentials across water meters in underground pipelines, demanding a sensor that was not only accurate and reliable when submerged but also extremely fast and energy-efficient to maximize the battery life of the remote logging equipment. The key challenge was to find a component that met these stringent performance criteria while also being compliant for use in potable water systems.
- Low-power data logging in remote water distribution networks.
- Requirement for fast, dual-pressure measurements to determine pressure drop.
- IP68 rating for complete, continuous submersion reliability in flooded chambers.
- Material suitability for potable water applications.
A manufacturer specialising in the design of low-power data loggers for remote environmental monitoring was developing a new system for the water utility market. Their data loggers, which utilise GSM/4G-NB-IoT and LoRa/LoraWAN communication protocols, are engineered for long-term deployment in the field where power is at a premium. The new application required the simultaneous monitoring of water pressure and the logging of pulses from a water meter, a common requirement for analysing water distribution network efficiency and detecting anomalies.
The specific use case involved installing two pressure sensors with each data logger, one positioned upstream and one downstream of a water meter within a pipeline. This setup allows for the calculation of the pressure differential across the meter, providing valuable insights into flow conditions and meter performance. The installation environments are often challenging, typically in underground chambers or vaults which are susceptible to flooding. Therefore, a primary requirement was for a pressure sensor with a robust IP68 ingress protection rating, ensuring it could be fully and continuously submerged in water without compromising its function or longevity.
Performance-wise, the sensor needed to have a very fast response. The customer specified a settling time of less than 20 milliseconds, which is critical for their low-power data logging equipment. A faster sensor allows the logger to wake up, take a measurement, and return to a low-power sleep state more quickly, thereby conserving battery life. The system could supply up to 12V, but a sensor that could operate efficiently on a much lower voltage was preferred to align with the low-power design ethos. An accuracy of 2% or better was sufficient for the application, and CE certification was mandatory for compliance. A crucial and nuanced requirement was that the sensor must be suitable for use in potable water systems. The customer was concerned about the sensor’s materials leaching any substances into the drinking water supply. While they were not familiar with the specific certifications, they needed formal assurance that the product would not affect water quality, a common requirement for components used by water utility companies.
The proposed solution was the TPTLRa series pressure sensor. This sensor was identified as an ideal fit due to its unique combination of features that directly addressed the customer’s highly specific technical requirements. The product’s suitability for use by water utility companies in flooded underground locations was a key factor in its selection.
To meet the critical low-power and fast-response needs, the 3-wire ratiometric output version of the TPTLRa was selected. This model operates on a supply voltage between 2.7 and 5.5 Vdc, well within the customer’s available power budget and perfectly suited for battery-powered IoT devices. Its current consumption is a mere 2.5 mA typically , and its response time is less than or equal to 10 milliseconds. This rapid response time easily surpassed the customer’s requirement of under 20 milliseconds, enabling the data logger to perform measurements with minimal power usage.
The sensor’s construction is purpose-built for harsh environments. It features a welded stainless steel housing and carries an IP68 rating, confirming its suitability for permanent submersion. The sensor is supplied with a specified length of robust, PUR cable that includes an integral vent tube for stable gauge pressure measurement. This integrated design ensures that the entire assembly, not just the sensor body, maintains its integrity when submerged, provided the cable end is terminated correctly within a waterproof enclosure.
The issue of potable water compatibility was addressed through material selection. While the TPTLRa series does not hold a specific drinking water approval like WRAS or DVGW as standard, its wetted parts are made from high-grade materials, including a stainless steel and EPDM seals. For many applications, a formal declaration of conformity for these materials is sufficient to satisfy regulatory bodies that the product is safe for contact with drinking water. Finally, the sensor’s standard accuracy of 0.25% FSO comfortably met the customer’s requirement of 2%.
TPTLRa Submersible Low Powered Fast Response Pressure Sensor
- Pressure Range: 0 to 10 bar
- Range Type: Positive Gauge (atm to +P)
- Output Signal: 0.5-4.5V (3-wire, ratiometric)
- Accuracy Class: 0.25%
- Electrical Connection: Submersible Cable IP68
- Cable Length: 5
- Cable Length Units: Metres (m)
- Housing Material: 316 Stainless Steel
- Seal Material: EPDM
- Diaphragm Material: 316 Stainless Steel
- Process Connection: G1/4″ male DIN 3852