SDI-12 Digital Network Card RS-485/ Modbus Network Card Copyright Keynes Controls 2015-2016 Tel: 0118 327 6067


This page shows the Keynes Controls single channel intelligent interface cards that can be used used to interface a wide range sensors to the SDI-12, 485 and Modbus over 485 digital networks.

The cards contain all the single conditioning and data acquisition components required to energise a sensor, make a measurement and transmit the data in engineering units across the chosen network. Full User Configuration option and calibration

The single channel cards take the difficulty out of converting a standard sensor into an intelligent device and take away all the difficulty for developing and testing software for the different networks.

60 mm 19.7 mm Download Q-LOG Download a free copy of Q-LOG at Daisy chained Network connection

In order to simplify card integration into projects, or to test with a new sensor, Keynes Controls offers a free Windows based Data Acquisition & Display Software named Q-LOG. This package supports all of the sensor interface cards and can be configured for 3rd party sensors and interfaces.

3.3 V DC + Vin - Vin 0 V Dimensions Free Q-LOG Data Display & Recording Applications Software

Q-LOG gives the User a fast and simple way to test our cards and make measurements prior to integration into data loggers and SCADA systems.

The standard single channel card dimensions are shown below.

The cards can be supplied for OEM applications So the dimensions can be changed to suit the application.

Contact Keynes Controls for further details.


Part No



+/- 5V single channel Card -       SDI12 network


+/- 500mV single channel Card - SDI12 network


+/- 250mV single channel Card - SDI12 network


+/- 50mV single channel Card -   SDI12 network


+/- 5V single channel Card -       RS485 network


+/- 500mV single channel Card - RS485 network


+/- 250mV single channel Card - RS485 network


+/- 50mV single channel Card -   RS485 network

Part No



Half Bridge with SDI-12 Comms


Full Bridge with SDI-12 Comms


Quarter Bridge with SDI-12 Comms


Half Bridge with 485 Comm Port


Full Bridge with 485 Comm Port


Quarter Bridge with 485 Comm Port

Standard Part Numbers Product Data Sheets

Part No



Potentiometer / Resostance  -       SDI12 network


+/- 500mV single channel Card - SDI12 network


+/- 250mV single channel Card - SDI12 network


+/- 50mV single channel Card -   SDI12 network


Temperature PT100/ PT1000 - SDI12/585 card

Precision RTD Sensors Modbus over 485 Network SDI-12 / 485 Network PC Data Acquisition USB Port Part No. USB-SDI12-Pro USB-485-Pro Isolated media converters All of the precision 4 Wire RTD sensors can be directly connected to any of the SDI-12/ 485 / Modbus networks using NP-RTD-4-RSD-1 temperature sensor interface card. Precision Temperature Measurements AquaDAT, CR800, CR200 CR1000 DataTaker Etc…. Customised Modbus Interface for Water level sensor Sensor Input This protects the devices dust and the ingress of moisture and water. All of the single channel cards can be fitted inside the custom environmentally seal plastic enclosure. Part No. NP-Case-1 Part No. USB-SDI12-Pro USB-485-Pro Isolated media converters Custom Enclosure SDI-12 RS-485 Modbus over RS-485 1 2 3 4 5 6 Const Curr Excitation 1 mA +V Sense -V Sense 0V Strain Gauge Measurements The circuit above demonstrates how a full bridge strain gauge is connected to a model NP-Strain-1 card. Any strain gauge based sensor such as load cells can be used. The measurements can be supplied directly in engineering units. Any third party data logger or network media converter can be used with the cards The image below demonstrates how the single channel cards can be fitted into the custom enclosure field based applications. Type PT-100/ PT-1000 Communications Options SCADA / Modbus / 485 Digital network






2 values in time tt given by stats



Raw data/ Engineering value & temperature values



Statistical values max S, min S, max T, Min T



Identification string



Calibration data  (No temp compensation - default)

E = [0] + [1]*s

with read back.

s is in mV

E is in engineering units



Ensemble Averaging Command

t → filter type

(should be 0 - mean only)

nn → number of filtered values 1 to 12

xxxx → interval between measurement * 200ms

Thermistior Linearisation Callendar - Van Dusen equations Sensor Interface card fits inside sensor housing Rt = R0[1 + At + Bt2 + C(t - 100)3] A,B &C are calibration factors Steinhart-Hart Calibration Factors Summary Supported Industry Standard Commands Low noise Precision Silicon Pressure sensor Ceramic Pressure sensor Pressure Sensors Elements Customised Pressure Sensor interface PCB Length - mm Width- mm Customised PCB for OEM / 3rd party applications

OEM Applications

All the cards shown on this page are designed and manufactured by Keynes Controls, and as such are available for customisation and OEM applications. Keynes Controls can supply units to fit directly into sensor housings and custom enclosures. Specify the length, width and maximum height available for a PCB when requesting this service.  

Displacement Sensor Interface Card SDI-12 RS-485 Modbus over RS-485 Digital Networks Draw Wire Sensor To Data Acquisition System or Logger Unit The displacement sensors cam be connected to the NP-Volt-1 voltage Input card. SCADA / Modbus / 485 Digital network Intelligent Sensor Development Intelligent Single Channel Interface Cards Keynes Controls Systems Contact US Go Home Strain Gage Cards SDI-12 Voltage - SDI-12/485 Crack Meter SDI-12 Potentiometer SDI-12 Temperature SDI12/485/Modbus Web Shop Leaf Wetness Sensor