Support Circuits for Air Quality Sensors

Alphasense (UK), established supplier of electrochemical gas sensors, also offers support circuits for the new ranges of A4 and B4 four-electrode sensors, together with a 4-20mA transmitter board for their NDIR CO2 infrared sensor.

Individual Sensor Boards (ISBs) have been built with lowest noise for the new B4 family of sensors, designed where best resolution at very low ppb levels is required in permanent fixed site networks. Requiring 3.5 to 6.4 VDC input, they provide buffered voltage output from both the working and auxiliary electrodes. Boards are pre-configured when you order for the type of sensor, with fixed zero and electronic gain. Each ISB supports one B4 sensor and requires less than 1.5 mA power.

The Analogue Front End (AFE) family of circuits is designed for use with the Alphasense A4 family of four-electrode gas sensors where space is critical, such as with mobile air quality monitors. Options include a 2-sensor AFE, 3-sensor AFE and 3-sensor +PID AFE.  All AFE circuits include a low noise bandgap to provide 200 mV bias voltage for NO sensors. Requiring from 3.5 to 6.4 VDC supply, the 3-sensor board for example only needs 2 mA power. Each board includes a Pt1000, providing 1mV/K signal for your software temperature corrections. The AFE can measure both oxidising (CO, H2S, NO, SO2) and reducing (O3, NO2) gas sensors; AFE configuration is specified when ordering.

Alphasense NDIR transmitter boards offer both 4-20mA and USB outputs. Concentration ranges can be recalibrated via PC/USB port using the proprietary software.

Technical Data Sheets can be downloaded from Alphasense’s newly updated website.