I don't think the probe actually emits negative voltage. I think the table is an example with voltages relative to some offset that the next section describes how to measure. Essentially, you're doing a 2-parameter calibration. If you're unsure, connect a voltmeter to the sensor before connecting it to the IOIO.
On Aug 8, 2017 9:11 PM, "Maximillian" <felix.c.sapu...@gmail.com> wrote: Hi All, I need to read pH using this product https://www.dfrobot.com/wiki/index.php/PH_meter(SKU:_SEN0161). I found this table on the description: [image: Ph-mv.jpg] The table said that it will give negative voltage (0.00 mV to -414.12 mV) for pH value 7-14.. I've been searching through this group, I think I found that I should not feed IOIO analog input pin with negative value (only 0v - 3.3v CMIIW). I'm not really experienced with electicity, so any suggestion is really a big help. Is there any solution for the negative value? Maybe using another componen to convert flip it to positive, or offset the voltage to be positive since it only have around 828mV range (-414.42 mv to +414.42 mV). So maybe I can just set the 7pH from 0V to maybe 2V, then the lowest voltage will only be 2V - 414.42mV, and the highest voltage will only be 2V + 414.42mV or any better/proper solution? Thank you. -- You received this message because you are subscribed to the Google Groups "ioio-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to ioio-users+unsubscr...@googlegroups.com. To post to this group, send email to ioio-users@googlegroups.com. Visit this group at https://groups.google.com/group/ioio-users. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "ioio-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to ioio-users+unsubscr...@googlegroups.com. To post to this group, send email to ioio-users@googlegroups.com. Visit this group at https://groups.google.com/group/ioio-users. For more options, visit https://groups.google.com/d/optout.
