The refractometer has built-in isolated 4–20 mA analog output channel, which represents the output of the refractometer. The output range and the engineering unit depend on the concentration curve used; for example, if the unit is configured with 0–100 °Brix output, the scaling of the output channel is 4 mA = 0 °Brix and 20 mA = 100 °Brix. The default error state indication level is 3.6 mA. The output is configurable: The output value (refractive index, temperature, concentration, quality factor), scaling, and error status indication level can be configured using the Vaisala Insight software and a USB adapter.
The connection header also has an RS-485 port. This allows using the refractometer directly as a Modbus RTU server device. Alternatively, the same port is used to connect the refractometer to an Indigo520 transmitter.
For digital communications, see Modbus RTU.
A sense resistor needs to be connected to the analog output. The HART host’s probes are connected across the sense resistor.