Zirconia oxygen sensor modules with standardized output

The FCX-MC type has built-in functionalities that meet some requirement in respect to certification without additional control electronics. The FCX-ML modules are simple modules with a low-noise amplification circuit that translates the µA signal from the sensor into a 4-20 mA standard output signal. Also, the module has a high-precision heater controller built-in for an accurate control of the heater voltage and current.

The accuracy of the FCX-ML module follows the accuracy of the sensor element itself. The resolution is determined by the sensor element or the amplification dependent on the application. As an example, the FCX-ML module combined with a FCX-UC sensor has a very good resolution and accuracy in a working point around 10-25% O2, but is somehow limited in resolution for oxygen concentrations below 5% O2. On the other hand the FCX-ML module combined with a FCX-UL sensor has a very good resolution and accuracy in a working point from 5000 ppm to 5% O2, but cannot give an output signal in air.

The FCX-ML OEM modules come with an integrated sensor/flow housing on the PCB board and hose connections, making it easy for the customer to integrate it into applications requiring forced flow. Standard is also a FCX-ML module with the oxygen sensor integrated onto the board, but with no flow housing. The latter form the basis for an oxygen transmitter, where the customer normally only has to apply a casing and the required cabling in order to build the finished transmitter. Another popular type, and standard in the Pewatron OEM module product program is a combination of board and sensor with a 30 cm cable connecting the two. The sensor itself is either delivered as a “free” element for customer specific built-in approaches or with in a flow casing for forced flow operation of the sensor.

All standard OEM FCX-MC modules come with the same possible configuration as the FCX-ML; i.e. integrated sensor/flow housing or sensor alone on the PCB board, plus sensor standalone or sensor/flow housing connected to the PCB board via a 30 cm cable. The difference between the FCX-MC and FCX-ML module is the extra intelligence built into the FCX-MC module. FCX-ML makes the amplification of the sensor signal direct via an amplification circuit, but the FCX-MC has a microcontroller integrated onto the PCB, which enables more accurate control of the heater and sensor signals, plus the possibility to store values in an EEPROM. The microcontroller allows for a certain watchdog function of the sensor and for a multiple of different analog and digital output signal formats to be defined. The FCX-MC OEM module comes standard with a linear 4…20mA output signal. By sensor heating errors the output signals show 0 mA indicating a broken sensor. FCX-MC OEM module also enables settings to be controlled and changed via a display box. Settings such as calibration and reset functions are enabled in the FCX-MC OEM module using the display box.

To summarize, the OEM modules come in two formats. The FCX-ML module with heater control and amplification of the sensor signal into a standard output signal. The sensor module output signal follows the logarithmic function of the oxygen sensor. The FCX-MC with amplification and linearization of the output signal, and including several functionalities for optimum usage of the module. Both types are delivered standard with solutions for forced flow or diffusion and/or with connecting cables between the sensor and the PCB board or with the sensor integrated direct on the PCB board. Pewatron has developed a number of customer specific solutions for any customer specific requirements outside of these specifications.