The WaterGuru unit uses a chemical pad and optical sensors to read it. The Sutro uses reagents. I’m playing with WaterGuru now, still within the 45 day return period. I’m not impressed. FC levels are consistently 1ppm below my Taylor tests, the flow sensor seems to be defective as I get as low flow alerts despite my pump running, clear debris basket, and plenty of flow past the sensor. It seems to have plenty of issues with WiFi and Bluetooth connectivity as it sometimes completely misses checking in at its scheduled test time, and on demand tests take anywhere from 10 minutes to 2 hours regardless of how you connect to the unit.
I’m working with their support but I’m likely to send this unit back unless they can fix the issues. I’m interested in trying Sutro but it’s very expensive.
Phin has an ORP sensor which is going to make it unreliable for measuring chlorine.