Low-cost and minimal conditioning interface for a PbSe photoconductor array [for pollutant detection]
A low-cost conditioning structure for PbSe photoconductor arrays with few components is described. We use a PbSe array of 64 pixels in a simultaneous atmospheric pollutant detector of several gases. The sensor system is based on infrared optical absorption spectroscopy. We present a second version of the sensor. We deduced: (i) it is necessary work at high chopper frequencies to reduce the effect of 1/f noise, (ii) a conditioning circuit is necessary for each channel, (iii) the conditioning interface must be near the array. Therefore, we propose to amplify and mix the incoming signal to produce a signal at a fixed intermediate frequency (IF), in our case 1 Hz. The circuit has few components which makes possible to place 64 conditioners in a small volume with SMT technology, 10/spl times/4.9/spl times/7.6 cm. The conditioner is divided into 8 boards. Each board has eight channels and an analog multiplexor. This permits to approach the circuitry to the array. Each channel conditioner has up to 100 dB voltage gain. Low IF technique makes possible to have high-performance circuits with low-cost components.