Variable Readings from ADC VP
Tim A
Posts: 1
Hi,
I am using the ADC Virtual Peripheral to read the analogue output from a pressure sensor.· My problem is that the value returned by the Javelin stamp (between 0 and 255) is fluctuating up and down when there is a constant voltage·connected to the analogue input of the circuit attached.· I am using 2 22K resistors and a 1 uF capacitor as suggested in the manual.· The value varies by around·6 units and there also seems to be an offset.
e.g. voltage measure at analogue input = 0.508 volts, expected value from Javelin = 26, recorded value from Javelin = 21-27.
The value on pin 9 (see attached pic) does not seem to be held constant at 2.5V (seems closer to 2.55V).
I have attached the pressure sensor circuit used as well.
Any suggestions/ideas you have would be great.
Tim
I am using the ADC Virtual Peripheral to read the analogue output from a pressure sensor.· My problem is that the value returned by the Javelin stamp (between 0 and 255) is fluctuating up and down when there is a constant voltage·connected to the analogue input of the circuit attached.· I am using 2 22K resistors and a 1 uF capacitor as suggested in the manual.· The value varies by around·6 units and there also seems to be an offset.
e.g. voltage measure at analogue input = 0.508 volts, expected value from Javelin = 26, recorded value from Javelin = 21-27.
The value on pin 9 (see attached pic) does not seem to be held constant at 2.5V (seems closer to 2.55V).
I have attached the pressure sensor circuit used as well.
Any suggestions/ideas you have would be great.
Tim
393 x 210 - 10K
497 x 663 - 37K
Comments
Any ripple on +Vs will appear on Vout, the larger C will lower that ripple.
regards peter