Modular Sensors for Versatility and FlexibilityApril 1, 2005 By: Thomas Griffiths Sensors
Leading-edge sensor suppliers are embracing a modular approach to sensor design. This methodology allows suppliers to use both their design and their manufacturing capabilities for markets where the use of several sensors is common. Customers benefit from both the flexibility and the cost savings that this approach provides.
In the broad context, modular sensors are product designs that can interchange a variety of different attributes including but not limited to different sensors, e.g., pressure and pH, sensor ranges, and packaging configurations. The benefit of the modular approach is cost savings. In many cases they occur immediately, and they tend to continue over time.
Electrochemical sensors for industrial applications are particularly well suited to the modular approach. Typical sensors for industrial process control measure contacting conductivity, pH, dissolved oxygen, and oxidation-reduction potential (ORP). Common applications of these sensors include wastewater control (especially for dissolved oxygen), water quality, boiler applications, utilities, and pharmaceutical manufacturing.
The typical mounting technique for industrial sensors uses a probe or electrode as the physical housing for the sensor that interfaces to the process. This type of assembly lends itself to a modular approach. The probes provide a millivolt or current signal to either a locally mounted instrument or a remote panel in a control room. The modularity concept can best be described at the instrument level. Two product types provide examples of available modular sensors.
Modular Analyzer Platform
The first example, the UDA2182 analyzer (see Figure 1), is Honeywell's most sophisticated approach to modular sensing. The analyzer provides a basic platform for the measurement of various process control parameters, where the user determines the configuration required for specific measurements and, based on the modular approach and the help of the analyzer, reconfigures the unit for different sensor measurements. The UDA2182 has single or dual input for pH, ORP, contacting conductivity, or dissolved oxygen, and accepts a dual input in any combination of measurements.
Figure 1. The UDA2182 dual-input analyzer provides a platform for modular sensing. Sensors include contacting conductivity, pH, dissolved oxygen, and oxidation-reduction potential.
The basic UDA2182 has a CPU card and power supply card—common elements that are required for acquiring sensor signals. Input cards for a specific sensor measurement are easily installed or changed depending on the desired measurement. The dual-input measurement system allows two simultaneous measurements, eliminating the need for a dedicated instrument for each sensor.
Factory precalibration of the input cards for the different types of measurement simplifies their installation. The user simply plugs in the desired card for the particular measurement as needed (see Figure 2). The instrument detects the type of card, e.g., a pH card, so it has all the information required to take the pH measurement automatically loaded to the instrument. This includes the menu and setup structure that are automatically set in the instrument. The pH sensor must be connected to a pH board for proper operation, but the mating of the proper sensor to its counterpart card makes it ready to operate—a modular match. It is an industrial sensing version of plug-and-play.
Figure 2. These examples of typical information displayed on the UDA2182 are pH in Input 1 (A) and conductivity in Input 2 (B).
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