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BioMed Signals - What to buy?

Which product is right for your exact requirements

BioMed Signals - What to buy?

Postby GalenEvans » Tue Jul 15, 2003 9:49 pm

Hi,

I am testing BioMed devices. Can you recommend equipment to measure and evaluate all of the following? Please note any required probes other than 1x/10x OScope probes.

1) Signals ranging from 0.15 mV to 5 mV at 4 Hz to 100 Hz. They are BioMed test patterns and patient simulations (ECG, EKG, Blood Pressure, etc), so the "frequency" is actually a wave form repeat frequency. The wave forms can be simple sine, square, and triangle waves, but also AAMI standard waveforms. The AAMI waveforms are made up of steps and ramps of about 0.5 mV, each lasting from 1 to 120 mSec, with the entire sequence repeated at 4 to 100 Hz. The measurements required are peak voltages and cycle repeat time interval. (Voltage measurement accuracy is important, 1% of reading being OK, 0.25% being excellent.) We would also like to eyeball evaluate "step flatness" and "ramp straightness." A printed 'scope sweep would likely be more than sufficient for this requirement.

2) 1 to 10 V at 4 to 100 Hz; square waves, 10 to 50% duty cycle. The required measurements are duty cycle (or pulse width is OK), rise time to nearest 0.01 mSec, and frequency to 0.01 Hz. (1% accuracy would be excellent.)

3) Sine and square waves; 1.000V and 1.000 second period (1 Hz). The minimum measurement accuracy and resolution is +/- 5 mV and 0.0025 Sec.

The emphasis on resolution and accuracy is because we have to document it for each measurement.

Thanks,
Galen Evans
Atlanta, GA. USA
GalenEvans
 

Postby markspencer » Wed Jul 16, 2003 7:55 am

Hi,

We do not recommend our products for medical purposes.

However, the unit which will meet your requirements is the ADC216. This unit has a 16 bit resolution, with a maximum voltage range of 20V. The voltage has a selectable range which will reduce the LSB value. The unit can measure 333ksps (166 kHz) on one channel and 166 ksps (83 kHz) when both channels are used. The units accuracy is 1%.

For a full description please visit here.

Picoscope software is provided free with this product as our upgrades from the web.

Best regards,

Best regards,
Regards,

Mark Spencer
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20 mV accuracy & resolution

Postby GalenEvans » Wed Jul 16, 2003 10:52 am

Hi,

Is the accuracy specification 1% of scale or 1% of value, i.e. for 20 mV scale, 200 microVolts; but for a 5mV measurement, still 200 microvolts? Would the 212 measure peak voltage of a 1V square wave with +/- 5 mV overall accuracy?

In the "High resolution oscilloscopes" application note I read, "... and a 16 bit oscilloscope is equivalent in resolution to a 4.5 digit 'benchtop' meter. " Will the meter or picoscope software with a model 216 actually display 4.5 digits (15-20 ppm)?

I find the accuracy specification, "1%" to be a bit terse. Is a more detailed "meter style" specification available? What I am looking for is a range by range, or parameter by parameter, specification in the form of "% of reading plus % scale" or some variation of that format that would allow max-error computation at a specific measurement.

Thanks,
Galen Evans
GalenEvans
 

Postby markspencer » Thu Jul 17, 2003 8:02 am

Hi,

The accuracy is 1% of the full scale. This means that the reading in the worst case senario will be 1% of the choosen range. It could be less.

Picoscope multimeter and scope view will only give you 4 digits. However, the ADC216 will provide more digits if you wrote your own software.

Unfortunately, I am unable to provide accuarcy results for all the scales available except for what I have said above.

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Regards,

Mark Spencer
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Postby GalenEvans » Thu Jul 17, 2003 9:39 pm

Hi,

Is the high resolution data available from the ADC216 via the excel macro?

Thanks,

Galen Evans
Atlanta, GA. USA
GalenEvans
 

Postby markspencer » Fri Jul 18, 2003 7:49 am

Hi,

The values returned by the excel macro are ADC counts which have to be converted into voltage. Therefore it would be up to you on how the result is displayed.

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Mark Spencer
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