SDI-TRANS-SENSOR24, SDI-12 Sensor Translator (24-Bit, 4 Channel)

Features:

► Fully SDI-12 Version 1.3 Compliant.
► Simultaneously measures up to 4 sensors with 24-bit resolution using a delta sigma ADC.
► ADC inputs are differential, and can be configured as single sided with a change to the input resistors.
► A wide range of sensor Voltage inputs can be accepted, by modifying the input resistors.
► On board temperature sensor, in addition to the 4 sensor inputs. User must calibrate.
► Low power operation with power consumption at less than 76uA in sleep mode.
► Has the ability to power sensors only when sampling.
► Wide input voltage range.
► Surge protection on sensor inputs.
► Each measurement can be adjusted with a scaling factor and offset. (out= scale*V + offset).
► Uses extended SDI-12 commands to set and retrieve all calibration parameters.
► Indicator LED for easy trouble shooting of SDI-12 systems. It can be disabled for low power battery operation.

SDI-12 Analog Sensor Translator Details

The SDI-12 Protocol Problem:
Although SDI-12 is a cryptic hardware and software protocol, it is still a widely used standard interface between environmental sensors and data loggers. Until now, sensor vendors have had the difficult and costly burden of creating their own SDI-12 solutions from scratch. Because of the many eccentricities of the SDI-12 protocol, it is a difficult task to create a truly compliant SDI-12 sensor interface.
The SDI-12 to Sensor Solution

Vegetronix has solved the problem of interfacing sensors to the SDI-12 bus by creating a small SDI12 Sensor Translator board which contains all of the necessary functionality. The SDI-12 Sensor Translator powers the sensor, and samples it with a high resolution ADC when it receives a measurement command from an SDI compliant data logger. The SDI-12 Sensor Translator handles all of the communication, and power down features of the SDI-12 protocol.

Figure 1 shows a connection diagram for utilizing the SDI-12 Sensor Translator. Single sided or differential outputs of up to 4 different sensors are tied to the inputs of SDI-12 Sensor Translator. The Translator contains connection points for power, ground and the SDI-12 data line.

Because of its small size the sensor can often be incorporated into the sensor housing. Alternatively it can be used externally. For sufficiently large quantities, we can provide custom board shapes to fit most any form factor.

Highly Precise 24-Bit Digital Sampling:
The translator uses a highly accurate 24 bit analog to digital converter to convert analog data from the 4 channels to digital values.

Customizable for Current Loop Inputs:
Many analog sensors have current loop outputs, which have the advantage of being loop powered, and do not suffer signal degradation with long cable runs. The SDI-12 Analog Sensor Translator is normally configured with voltage reading inputs, however, it can be customized to read current output sensors, by changing the input resistor network on the boards. We have instructions below on how to do this, or we can do it for you here at our factory. Just contact us before placing your order to let us know, that you would like this customization option.

Optimized for Low Power Operation:
The Translator is extremely low power with only a 76uA current drain when it is sleeping, and it provides sensor power control, so that the sensor only receives power during a measurement cycle. This is useful for creating battery powered sensors.

Diagnostic LED for Fast Troubleshooting:
An LED indicator makes initial system configuration and debug easy. The LED will light whenever it receives an SDI-12 command. The LED can be enabled or disabled with an extended SDI-12 X command.

Fully SDI-12 Compliant:
All standard SDI-12 commands are supported. In addition, it has extended commands which can be used to calibrate sensor outputs.

Our Translator has been fully tested with the NR Systems SDI-12 Verifier.

Customizable Calibration:
Each of the measurements from the 4 input channels can be scaled and offset with user supplied calibration coefficients. This allows you to automatically convert the data, from a voltage into meaningful units.

Internal Temperature Sensor:
In addition to all these features the SDI-12 Sensor Translator has an on board temperature sensor, that you can calibrate to your application.

Optional Case:
- To keep the cost low, we sell the board by itself, or you can optionally pair it with an enclosure.
- The enclosure is made of 3D printed PLA.
- The top part is of the case is transparent, enabling you to see the internal LED.
- The bottom part has flanges with mounting holes, making it easy to mount.

Applications:
    Crop Steering.
    Ultra-fast prototyping of SDI-12 Sensor networks.
    Increasing time to market implementation of sensors.
    Protocol bridging.