I2C Sensor Isolator
Electrically isolate your sensors for better readings
- Regulated and isolated 3.3V power output from 3.3 or 5 V input
- Isolated bi-directional I2C up to 100kHz max frequency
- Based on Analog Device’s ADM3260
What it is
Take measurements from several probes at the same time while connected to the same device. Probes often interfere with each other and cause shifted readings. The environment could also be causing readings to be off, likely due to a ground-loop or other electrical noise. Using this will eliminate those problems.
There are two sides, referred to as the INPUT and ISO. The input side is the four pins of your I2C bus; either 3.3 V or 5 V power, ground, SCL, and SDA. Connect them to your master controller. The ISO side is the output side and should be connected to whatever device you want to keep isolated and is supplied with 3.3 V.
The most basic configuration would be the sensor isolated from the master.
<I2C master> - <ISO> - <sensor>
You can connect more than one device to the ISO side. In this configuration the sensors will be isolated from the master, but not from each other.
<I2C master> - <ISO> - <sensor> - <sensor>
If isolation from the controller isn’t required, but isolation from two different probes is, you can connect the ISO board between the sensors only.
<I2C master> - <sensor> - <ISO> - <sensor>
And then there is everything is isolated from everything.
<I2C master> - <ISO> - <sensor> - <ISO> - <sensor>
But do I need one…
It’s hard to answer. The short answer is you probably do.
- you will if you are using different probes through the ISE interface (like pH and ORP)
- you will if your sample has ground-loop problems
- you will if something is introducing electrical noise into your sample
- you might not if you are using the ISE and EC boards together. The EC board causes a small (usually) linear offset of your ISE reading. It makes calibration more complicated and is generally a hassle to deal with.
You will know you need isolation if you are getting bad readings when another probe is either introduced or taken out of your sample, or if you are getting skewed measurements intermittently (like when a pump is turned on or off, or maybe even when you touch the water), or otherwise unexplained measurement swings.
I2C Sensor Isolator
Support and Questions
If you have questions, find a bug, or have any suggestions you can send an email to [email protected].
Schematics are open and CERN OHL licensed.