Tunable Filter Implements Highpass, Lowpass, Bandpass

A new instrument has been developed to implement highpass, lowpass and bandpass filters. The Model 601 tunable highpass/lowpass filter contains a tunable 8-pole Butterworth highpass filter followed by a tunable 8-pole Butterworth lowpass filter. Both filter responses are flat in the pass band and roll off at 96 dB per octave beyond the corner frequency. Corner frequencies can be set from 100 Hz to 40 kHz at the front panel or over a serial link from a PC. The unit is controlled by a Microchip PIC16F873 microprocessor and includes an input analog anti-aliasing lowpass filter, a variable gain output amplifier and an analog lowpass output filter. The microprocessor is in sleep mode when not programming the filters so its clock does not add any output noise. Single quantity price for the Model 601 filter is $587 plus shipping. For more information, contact Ron Tipton at TDL TECHNOLOGY INC., Las Cruces, NM. (505) 382-3173.