Hello,
I am working on a sensor which produces varying voltages with 5V power. I used another ADC and multimeter to give about 1.24V. However when using the ADCPi the readout is around 3.1V. I have not made any modifications on demo_readvoltage.py or ADCPi.py. Is there any conversions I have to make in the code?
I plugged into terminal + and - of all channels it seems to be giving same voltages. I have two ADC Differential Pis and tried on both they gave same numbers so I believe it is the code's problem.
Please help. Thanks!
Problem with voltage readout
1382 Views - Created 04/03/2019
04/03/2019
Posted by:
landelifestyle1
04/03/2019
Posted by:
andrew
Location:
United Kingdom
Hello
With the ADC Differential Pi, you will need to use the ADCDifferentialPi.py library instead of the ADCPi.py library.
The ADCPi.py library is designed to work with our ADC Pi boards which have a voltage divider on the inputs. The library multiplies the input value by 2.471 which is why your 1.24V is displaying as 3.1V.
With the ADC Differential Pi, you will need to use the ADCDifferentialPi.py library instead of the ADCPi.py library.
The ADCPi.py library is designed to work with our ADC Pi boards which have a voltage divider on the inputs. The library multiplies the input value by 2.471 which is why your 1.24V is displaying as 3.1V.
04/03/2019
Posted by:
landelifestyle1
Thanks Andrew! May I ask what the ADCPi is for then? I do not see a product that you have that is jusr ADC Pi.
04/03/2019
Posted by:
andrew
Location:
United Kingdom
We have this ADC Pi board which is almost the same as the ADC Differential Pi but with voltage dividers on the inputs to increase the voltage range.
07/03/2019
Posted by:
landelifestyle1
Thanks! I assume it is ok to stack up the ADC Pi and ADC Differential Pi. I know that the ADC Pi is single ended output, if I already have three ADC Differential Pis connected to sensors would noise be a big problem fro the ADC Pi? (I am trying to maintain the 0.05% accuracy)
07/03/2019
Posted by:
andrew
Location:
United Kingdom
You can stack the ADC Pi and ADC Differential Pi on the same Raspberry Pi. As they both use the same ADC chip you can only stack 4 boards in total so if you have three ADC Differential Pis you will be able to add one ADC Pi to the stack.
Each ADC chip has its own internal voltage reference which is accurate to 0.05% so you shouldn't have any issues using the ADC Pi and ADC Differential Pis together.
To get the best accuracy you will need to make sure your power supplies are stable as noise on the power lines could reduce the accuracy of the ADC inputs.
Each ADC chip has its own internal voltage reference which is accurate to 0.05% so you shouldn't have any issues using the ADC Pi and ADC Differential Pis together.
To get the best accuracy you will need to make sure your power supplies are stable as noise on the power lines could reduce the accuracy of the ADC inputs.
07/03/2019
Posted by:
landelifestyle1
Hi Andrew, Thanks for your reply! I am planning to put 4 ADCs together, that solves my problem. Thanks!
Note: documents in Portable Document Format (PDF) require Adobe Acrobat Reader 5.0 or higher to view.
Download Adobe Acrobat Reader or other PDF reading software for your computer or mobile device.