I'm building a prototype Raspberry PI based measurement device which will sense pulse rate/skin temperature/galvanic skin response (GSR) and so I'm looking to use one of the ADC devices to cover off all these inputs (it doesn't need to be highly accurate and it won't be used in a medical use - I just need it to detect the pulse and changes from a base level for the other areas).
I'm planning to base the finger pulse detection based on the photoplethysmography techique (detecting the change in IR levels at the fingertip) using either a device similar to the Keyes KY-039 (http://www.ebay.co.uk/itm/5V-Heartbeat-Sensor-Senser-Detector-Module-By-Finger-For-Arduino/181938071824) or a VISHAY TCRT1000. This latter one looks better from a mounting perspective as I don't really want a fingertip type holder sticking above the housing and it looks like the keyes style one will require this for the IR emitter. Has anyone experience of these?
The Arduino examples seem to hook the output from the device directly to the input of the AD convertor but many examples of standalone devices need several op-amps in between to amplify/apply differentials so just wondering whether I'll need this extra circuitry (and whether I need to build similar for GSR)?
Will the ADC-Pi Plus (or for a limited input the ADC-DAC) be the best option or is there an advantage in using the ADC Differential board?