WattmonPRO is an embedded data logging and control device. This version has several I/O lines on-board, making it easier to develop intelligent machine automation applications in addition to performing data logging.  The device comes with 128KB of RAM which allows for up to 50 data points to be logged.  To read about our more powerful device, see WattmonMEGA.

Wattmon is a versatile platform which can be configured for countless applications. The inbuilt web server provides all of the tools necessary to customize the device. No programming is required to set up actions based on various triggers, which can control I/O lines, send emails and more.


WattmonPRO Datasheet

Power Requirement

WattmonPRO can run on a DC power source between 6 and 60V DC. It has a built in high efficiency switching buck regulator that ensures that it consumes less than 2 watts of power without accessory devices. The device can be shipped with an AC adapter or a DC power cable to be directly connected to your battery bank of up to 48V DC.


WattmonPRO has two ways of connecting to the Internet. The built-in LAN can be connected directly to a laptop or router, and is used for setup and local monitoring. The USB Host port works with a selected number of USB Cellular dongles, allowing both outbound and inbound data via the Internet. Although we provide instructions on configuring your local dongle, not all of them work. Need a compatible USB dongle for remote monitoring? Use one of our Huawei dongles, the E303F or E3531

Hardware Features

Serial (RS-232)

An RS-232 serial port allows you to interface with Inverters or other devices that can provide data. Drivers for Studer and Victron inverters are now provided along with the Wattmon, making it simple to remotely monitor your PV panels and energy information from the inverter itself.

Modbus RTU (RS-485)

An RS-485 Modbus RTU interface is built in and Wattmon acts as a Modbus master to collect data from various devices such as power meters, current sensors, etc.

If you are planning to monitor a battery bank with Wattmon, you will require a current sensor device such as the C252 (25A), C502 (50A) or C752 (75A).

Inputs and Outputs

The inputs and outputs and their various applications are described below.

4 digital inputs

Pings 16-19 are digital inputs. They are opto-isolated and can handle anywhere between 4 and 24V DC between the input pin and the DIGND pin. Pins 16-18 (DI1-DI3) can also be configured as pulse/frequency counters for measuring data from flow meters/anemometers, etc

4 digital outputs

These are open collector type (using a ULN2003 chip) and can be directly connected to 12V relays (with external power supply) to control high power loads - they can handle up to 500mA per pin.

Onboard relay

An on-board latching relay can switch DC or AC loads of up to 5 A. If higher loads are required, this relay can be used to power a larger one. The latching relay takes very little power to switch state and no power once toggled, so there is no difference in power draw whether the relay is on or off.

3 Analog inputs

WattmonPRO has three analog input channels, each with a 10-bit ADC on board (1024 possible values for the full scale).

Channel 1 also doubles as the voltage supply for the device. This is done so that when the device is running of a battery it's possible to measure the battery voltage directly from the supply. Max voltage is 60V DC.

Channel 2 is a voltage sense input that can be used to measure up to 330V DC for high voltage battery banks. The negative voltage terminal is shared with the main ground on pin 1.

Channel 3 is used to measure up to 5V DC, perfect for sensor inputs from devices such as the PYRA300 Solar Irradiation Sensor or pH meters.

Onewire Bus

WattmonPRO has a Dallas Onewire bus that allows for DS18B20 temperature sensors to be connected. This can be used for ambient temperature or battery temperature measurement. You can connectup to 8 sensors per device. See here for more information: Onewire Temperature Sensor

Standard Compliance

WattmonPRO is classified as a device for Industrial use. The device complies with the following standards:
IEC-61000-4-2 - Electrostatic Discharge
IEC-61000-4-4 - EFT Immunity - 1kV
IEC 61000-4-5 - EMC Immunity - 1kV
CISPR 11 Class A - EMC


Supported Cellular Dongles

Huawei E303C

Huawei E3531

Huawei E3531-s2

D-Link DWM-156

ZTE 180


Pinout Diagram


Typical Application Diagrams

Monitoring Battery Banks of Upto 48V DC

The following diagram shows the components required to monitor battery banks of up to 48V DC. Depending on the current, the C252 or C1002 Dual Current Sensor  could be used.

Diagram: Monitoring battery bank setups of up to 48V DC

Monitoring Battery Banks of Upto 330V DC

The following diagram shows the components required to monitor battery banks of up to 300V DC. This requires an additional AC to DC or DC/DC power adapter to power the WattmonPRO device.

Diagram: Monitoring high voltage battery banks (up to 330V)

Monitoring Temperature

Wattmon works with all Onewire DS18B20 temperature sensors.

Diagram: Monitoring temperature with external sensor(s)

Pulse Counting and Water Flow measurement

There are 3 digital inputs with pulse counting capability, which can be used to measure wind speed, water flow, or anything that generates a frequency.

Diagram: Pulse counter input to measure water flow

RS-485 Modbus RTU

Any third party Modbus RTU compliant device can be hooked up to Wattmon using the following diagram:

Diagram: RS-485 Connectivity

RS-232 Serial Interface

Legacy devices or some brands of inverter such as Studer and Victron can be connected up using RS-232.

Diagram: RS-232 DB9 Connection Diagram

Monitoring Solar Irradiation

The PYRA300 irradiation sensor provides a 0-3V analog output. This can be connected as shown below. Any other analog (0-5V) signal can be hooked up in a similar manner.

Diagram: Monitoring solar irradiation

See how WattmonPRO works for Inverter Monitoring Inverter Monitoring.

For more information, see the WattmonPRO Datasheet

Wattmon Add On Devices