Description
The purpose of the SDI Multi Sensor Module with Charger is to provide a low power temperature compensated battery charge controller and a general-purpose interface for analog sensors.  Sensor and charge controller data are acquired via the SDI-12 port.  The 410 module provides sensor expansion capabilities for the GTX capabilities as well battery charge control.   

There are six analog sensors configured. These are:

• Solar Panel Voltage
• Battery voltage
• Battery charge current
• First user defined single ended analog input or Internal enclosure Relative Humidity
• Second user defined single ended analog input or external thermistor
• Third user defined single ended or differential analog input, (Water Level PT or barometer).

 
The 410 also contains three SDI-12 3-wire (power / ground / data) interface connectors, which allows for three SDI-12 devices to directly connect to the SBCM SDI-12 BUS. All three connections are in parallel. A block diagram of the SBCM is shown above with barometer, thermistor and internal RH in place.

Analog Sensor Inputs

The basic analog measurement is a 12 bit ADC integrated with the Microprocessor.  It may be operated in either an absolute value or ratio metric mode.  The later is used for resistive type measurements commonly found in temperature measurements or in pressure sensors used for water level or barometer measurements.  The measurement process in the SBCM has its own unique scale and offset values.  Default is a scale of 1 and offset of zero. 

The maximum number of available sensor inputs is eight.  Six are configured in the standard configuration.  Three are committed to operation of the battery charge controller.  One may be used as an analog input.  (FS is 2.2 volts).  A second is configured as a single ended analog that may be set up to use thermistors for temperature measurements (see US Sensor or YSI).  The third may be set up either as a single ended or differential sensor input. 

Using US Sensor or YSI thermistor probes accuracy to 0.1 C may be attained for water or air temperatures.