The CAEN ELS AMC-PICO-8 is an eight channel picoammeter AMC board in MTCA.4 format. The analog front-end allows measuring bipolar currents up to ±10 mA (different ranges available) with maximum sampling rate of 1 MSPS.
The analog front-end is composed of a specially designed transimpedance input stage for current sensing combined with analog signal conditioning and filtering stages making use of state-of-the-art electronics. The 20-bit resolution is obtained from independent, simultaneous sampling and low-delay SAR (Successive Approximation Register) Analog to Digital Converters (ADCs).
Different versions are commercially available.
Each channel has two full-scale measuring ranges, up to ±1 mA and ±1 µA (AMC-PICO-8 version, with bandwidth of 10 kHz) or up to ±10 mA and ±500 µA (AMC-PICO-8-C2 version, with bandwidth of 300 kHz) and the current source can be floating up to ±300 V respect to the chassis ground. The floating capability of the inputs is perfectly suitable for applications where the detector or current source needs to be biased.
The analog front end is designed in order to achieve LOW NOISE, LOW TEMPERATURE DEPENDENCY and extremely SMALL UNBALANCE BETWEEN CHANNELS.
The analog characteristics are further improved with calibration. Calibration data are stored in the on-board EEPROM memory and are loaded in the signal-processing logic on power-up.
The on board Virtex-5 FPGA performs the conversion from "raw" values acquired from ADCs to a single-precision floating point numbers, representing the measured current in amperes. The floating point format is highly suitable for additional post-processing. The signal-processing logic can also be configured to capture the signal on certain trigger condition. Additionally, the internal memory can also be programmed to store data before trigger condition happens, providing a valuable data to user.
The communication with Virtex-5 FPGA is performed with the PCI express bus. All system parameters (e.g. analog front-end range, sampling frequency) can be achieved by writing to appropriate registers from PCI express. The FPGA also embeds a Scatter-Gather DMA which can be used to transfer data to PCI express root port (e.g. CPU).