ADAS1000 FAQ Index
AC Lead Off Operation
Thank you for the nice compilation. I have few questions on ADAS1000-3/4.
1. Can the analog inputs be configured as digital/single ended mode and used to measure 'V' leads?
2. Can the AFE be configured different modes ( Analog/Digital/Single ended) between two captures without resetting the device?
3. What is the drive strength ( current) of Shield Drive and RLD Drive?
Thanks for message.
1. In single ended mode, any electrode can be applied to any input, with the output of the ADC = ECG input - CM amp output. The CM amplifier output can be configured to whatever you want, typically this would be WCT.
In digital lead mode, a lead calculation is performed after the ADC, the digital lead calculation is fixed, so CH1 = ECG1 - ECG3, CH2 = ECG2-ECG1 and CH3 = ECG2-ECG3. Therefore depending on what you are referencing the V lead too, the digital lead mode may/may not be suitable.
2. It's not intended to change operational modes on the fly. While you would not need a reset in between changing modes, there might be some settling as the channel changes to another mode, this would likely be seen as a disturbance in the ADC results.
3. The Shield driver is not expected to drive much current, it's just biasing the shield of the cable. The RLD drive is similar, it's not intended to drive much current either, also, it will be driving the patient, so there will always be an external patient protection resistor in series to limit the current pushed into the patient as dictated in the medical standards.
Does Shield drive and RLD drive same ( derived from same source)? We have seen with our experiment using RLD as shield provides better immunity to noice issues. Also, there need to be certain current ( may be in nA) to drive these shiels, it cant be just a voltage reference. You may like to verify this.