Product category:
Stepper and Servo Drives, Motors, Controls
News Release from: Delta Tau UK | Subject: Acc36UK sigma-delta board
Edited by the Engineeringtalk Editorial
Team on 18 July 2007
ADC board offers high resolution and
speed
The maximum update frequency of the AD7763 is 625kHz or 625,000 samples a second.
Recognising the need in some applications for a higher performance analogue to digital processing for its UMAC motion control system, Delta Tau UK has introduced the new Acc36UK sigma-delta board Higher resolution, faster conversion speeds and better common mode rejection (CMR) were all important objectives to be addressed in a new analogue to digital conversion (ADC) board design
This article was originally published on Engineeringtalk on 19 Jun 2000 at 8.00am (UK)
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To achieve the desired performance, the analogue input device chosen was a single-channel instrumentation amplifier, AD8221.
This high-performance device has a number of advantages over operational amplifiers (Op Amps), including giving high CMR.
CMR is the ability to cancel common signal - such as noise that appears on the differential inputs - and as a result only differential signals are amplified.
The analogue to digital convertor selected was the AD7763 Sigma-Delta convertor from Analog Devices.
The output of the AD8221 is fed to the A to D convertor.
This device is a 24-bit convertor with in-built gain and offset registers as well as a series of low-pass filters.
These filters can be configured to optimise the output bandwidth relative to the input clock frequency.
The maximum update frequency of the AD7763 is 625kHz or 625,000 samples a second.
Depending on the number of filters implemented various data rates can be achieved.
The data from all the channels is then synchronised and shifted serially into hardware registers on a micro controller and thereafter into dual ported RAM and onto the Delta Tau UBUS within the company's UMAC motion controller.
An optically isolated clock from the micro controller allows user-selectable update times.
Together with three internal filters the new Acc36UK has improved resolution and reduced noise when operating at 24 bits and will update all 16 channels to the dual-port RAM during UMAC's servo update time.
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