pH meters are traditionally hands-on devices, used within a fixed physical location. Increasingly, R&D organizations are looking for real-time measurements, acquired with little or no human intervention, often from remote locations, in a format compatible with simple data logging software, laboratory information systems (including LIMS and ELNs), or enterprise-wide data management systems.
Wireless-enabled pH probes address these needs, and in most cases provide their own data management capabilities and analytics beyond pH.
Process industries have been enamored with at-line or inline analytics for decades. Endress+Hauser, a manufacturer of analytical, laboratory, and process probes, estimates that 30 percent of quality-related assays in foods, chemicals, pharmaceuticals, and other process industries involve pH measurements. Remotely located, wireless pH sensors have similarly changed the game for monitoring the status of wastewater, drinking water, and environmental remediation sites, and fueled the trend toward real-time collection and remote acquisition of data.
Remote pH probes often incorporate sensors for two or more additional parameters; for example, turbidity, temperature, conductivity, dissolved solids, etc. Acquiring this data remotely greatly expands coverage for a monitoring site and replaces several instruments with one probe, while harmonizing data collection from multiple sources.
Remote sensing generally demands a higher level of trust than is required for instruments monitored at the point of use. With probes and associated instrumentation out of sight, operators cannot immediately tell if something has gone wrong. pH sensors deployed remotely should therefore exhibit very low drift over time. For example, In-Situ (Fort Collins, CO) claims that its Aqua TROLL 500 multiprobe remote pH sensor drifts no more than 0.1 pH unit every 125 days.
Most pH sensors capable of wireless data transmission also perform data storage and processing on the device itself. pH sensor probes from Turtle Tough (Victoria, Australia) incorporate on-board sensor memory that stores calibration, configuration, and service history, enabling both onsite and remote utilization of that data. Storing information both onsite, and having it available remotely, eliminates day-to-day interaction between users and sensors, while “greatly simplifying the change-out of sensors,” the company says on its website.
Remote data logging for traditional electrode-based pH meters has been available for some time, in both built-in form and as an add-on. Numerous vendors offer wired (e.g. LAN) or wireless (most often wifi but also cellular and Bluetooth) pH sensors, for both standard electrode and solid-state pH probes. Many models include an SD memory storage card to back up data when the wireless is down or experiences radiofrequency interference.
For example, the HALO® wireless soil pH meter from Hanna Instruments (Smithfield, RI) features a built-in temperature sensor that transmits “laboratory-grade pH and temperature measurements“ directly to mobile devices through Bluetooth. MicroDAQ (Contoocook, NH) offers its Bluetooth pH and temperature data logger, a field-worthy instrument suited to long-haul measurements, which stores up to 43,000 pH measurements for backup or emergencies. MicroDAQ also sells generic wireless data loggers for use with a wide range of instruments. JUMO USA (East Syracuse, NY), which offers a broad line of liquid and process measurement systems, sells the JUMO digiLine pH sensor-transmitter interface, which screws onto the company’s pH probes.
Remote logging, more or less free of human intervention, provides greater spatial and temporal coverage of an event, be it a drug production line or the status of a Superfund site. By interfacing directly with information management systems, wireless also assures data integrity—no more paper notebooks and no more lost or mis-transcribed readings. Going wireless also assures you’ll never ask, “was that a seven or a one?”