Q
My questions to ADAS1000-4:
a) Does ADAS1000-4 also work with only two electrodes e.g. LA and RL ?
b) How does the respiration measurement (respiration-path) work and where do
you have to connect the three outputs/inputs ?
c) Does each ECG input channel an own high-pass filter?
d) Can you configure/adjust the high-pass filter?
e) What is the function of Shield Drive Amplifier? We want to connect the
shields to GND.
f) Could you send example source code written in C or C++ for ADAS1000-4?
g) Can we provide a standard connection diagram?
A
a) The minimum number of electrodes required for ECG measurement would be 3, so
2 ECG electrodes, e.g. RA and LA and the RLD. This would give a one lead
measurement. If RLD is not used, then the CMRR performance will degrade which
will affect the quality of the ECG measurement.
It really depends on what your customer is trying to do, the type of ECG
instrument they are trying to develop. Note that an ECG measurement is always a
pair of ECG electrodes, e.g. RA/LA…. Etc.
b) The respiration measurement is made on a pair of electrodes (a lead). This
pair of electrodes can be the ECG electrodes, e.g. LEAD I/II/III. Page 34 of
the datasheet provides a detailed description but in summary a programmable
high frequency differential current is driven out onto two electrodes and. The
resulting impedance variation caused by breathing causes the differential
voltage to vary at the respiration rate. The current is AC coupled onto the
patient. There is a shallow modulation envelope that equates to the respiration
frequency. RFI filtering, ESIS filtering in addition to the cable impedance
will affect the ability to measure this small ohm variation in the presence of
a large series resistance, Table 13 on the datasheet gives you the maximum
allowable cable and thoracic loading.
c) Low pass filtering is covered by the ADAS1000 (e.g. on chip
40Hz/150Hz/250Hz/450Hz) For HP (0.5Hz/0.05Hz) or Notch (50/60Hz) this would be
something likely better done in the digital domain by yourself.
d) See above.
e) It is used to drive the shield of the ECG cables. It can be disabled if not
used.
f) There is in fact some ucontroller code available. This should provide some
insight/starting point. Please take a look at
http://wiki.analog.com/resources/tools-software/uc-drivers/renesas/adas1000
g) http://www.analog.com/static/imported-files/circuit_notes/CN0308.pdf In this
circuit note there is a very useful connection diagram. It can be applied to
the ADAS1000.
Please also note that the evaluation board hardware is for use only for
evaluation purposes, it was not designed to be connected to humans or animals.
In terms of ADAS1000 configuration, it demonstrates the key elements in terms
of decoupling and possible configuration for a 12-lead solution. However,
please note it is not intended as a reference design. The component selection
used on the evaluation board may not be suitable for end system use. The
evaluation board schematic has not been tested against defib/esis signals. The
end system design and component selection is the responsibility of the system
integrator.