Stanford SR600 Frequency Counter

The SR600 Series consists of three dual-channel instruments. Each instrument channel has a low-noise preamplifier, a precision high pass or low pass filter section, and an output amplifier. The filters are 8-pole, 6-zero elliptic-type with 115dB per actave rolloff, 0.1dB of passband ripple, and 80dB of stopband attenuation. Cutoff frequencies can be set between 1Hz and 100kHz making the SR600 series ideal for applications including anti-aliasing, audio analysis and frequency-domain signal conditioning.

Features:

• Two independent filter channels
• 115dB/octave rolloff
• 1Hz to 100kHz frequency range
• 0.1dB passband ripple
• 6nV/√Hz input noise
• Up to 80dB of gain
• GPIB and RS232 interfaces
• SR640 - Dual Low Pass
• SR645 - Dual High Pass
• SR650 - High Pass/Low Pass (can be cascaded for Band Pass)

Each filter channel has a floating, differential input with 1MΩ input impedance and 6 nV/√Hz of input noise. The analog ground for each filter channel is available at a rear-panel BNC connector to provide complete flexibility in grounding. The filter grounds may be tied to the instrument's chassis ground or to any other point. Both AC and DC input coupling can be selected, and an invert key allows the phase of the signal to be shifted by 180° with a single key press. Up to 60dB of preamplifier gain can be specified in 10dB increments. A simple offset adjust screw lets you null DC components in your signal.