KAD/ADC/117/EC1

The KAD/ADC/117/EC1 has eight channels of signal conditioning and data acquisition for differential voltages, strain gage, and bridge measurements. In addition to the measurement channel, the KAD/ADC/117/EC1 provides independent constant current excitation for up to eight channels. Each differential-ended signal has a separate programmable amplifier, filter, and A/D converter.

At the heart of the KAD/ADC/117/EC1 is a hard-wired state-machine that over-samples all channels and digitally filters any noise above the user-programmable cutoff frequency. This is achieved using cascaded, half-band, decimate by 2, 15 tap, Finite-Impulse-Response (FIR) filters with 32-bit coefficients followed by an 8th order Butterworth (IIR) filter with a default cutoff point set to 25% of the sampling frequency. The IIR filter is bypassed in FIR mode with samples output directly from the FIR filter. All signals are sampled simultaneously. Thus, when several channels are sampled at different sampling rates, at least at the start of an acquisition cycle all channels will be aligned.

The excitation current is programmable (0 mA to 20 mA in 5 µA steps) and is kept constant. As the resistance changes, the voltage across the bridge (and hence as seen by the amplifier) changes linearly.