Hello. I'm trying to interface the 0-10VDC analog ports on the Apex to an Arduino to issue dosing commands for fert and pH buffer (it's just a project I'm doing). I'm using V3/V4 with a 12kohm+12kohm resister network between the positive and negative rails for each analog channel (i.e. V3 and V4 separately) and taking a centre tap on each network to the Arduino so it only sees 0-5VDC - see simple network below. When measured independently with a voltmeter, both circuits provide 5VDC, however, when both connected to the Arduino and hence negative rails are joined due to common GND on the Arduino, one channel measure 5VDC and the other 10VDC - I'm sure this is because of the Thevanin resistance equivalent so I used diodes to prevent current from one channel interfering with the other. Made things worse.
Does anyone know whether the 0-10V channels are earthed separately in the Apex. Has anyone successfully done what I'm trying to do and willing to share?
Cheers in advance.
Apex-Arduino.jpg
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