PR33-15 - NDVI light sensor


I am integrating the PR33-15 with our ESP32 based edge architecture for robotics. I2C is fine, I’m happy accessing the readings in the device.

I was hoping to get some more information on best practices when connecting to a 2-wire passive analogue device - it is essentially a photodiode which outputs a microamp output or mV output with a resistor. I am hoping to read this value on the PR33-15 (well 2 signals on 2 channels actually) as we are calculating NDVI. The sensors are quite pricey, so definitely don’t want to damage them, by powering them or similar.

Attaching the documentation for the sensor - 2 CHANNEL LIGHT SENSOR-SKR 1840-DATASHEET.pdf (641.4 KB)

Anybody got helpful suggestions on how to go about this integration in a safe way?


Kristof @

i don’t see any info regarding the 4-20mA signal in both datasheets.

I agree, this is not well documented. I have found a wiring guide for a very similar sensor:

My main concern is making sure the PR33-15 doesn’t provide voltage on it’s output and thus damage the diodes:

So this sensor doesn’t need any power. its like a phototransistor. generates a small amount of current proportional to the light.
You will need this produt

Add a 10Kohm resistor and that will convert the mA into voltage.


Hey Bhaskar, thanks a lot for your quick support!

Much appreciated.

@Bhaskar just another thought.

The reason we chose the PR33-15 was to amplify the signal. Is there a way to ensure no voltage is applied on the channels of PR33-15.

I can use an ADS1115, but may lose resolution due to small input amplitudes.

Thanks again.

The input signal is micorvolt. ADS1115 has internal gain settings which can read microvolt signal.
You can amplify the signL using the resistor.