Home of the ICON - Instrumentation and Control Over Networks Last updated April 1, 2007

     ICONIO Board
     1-Wire I/O Devices

     ICONIO Card Installation
     ICONIO Programming

     Basic 1-Wire Installation

     2 Chan Counter (OWCTR2)

     2 Chan A-D (OWAD2)

     4 Chan A-D (OWAD4)

     1 Chan Pot Out (OWPOT1)

     Dry Contact (OWRELAY4)

     Connections (OWCONNECT)

     Temperature (OWT)

     Relative Humidty (OWTRH)

     Light (OWL)

     Weather Station (OWWEATHER) 


     Phone: (406) 599-1053

4 Channel A-D (OWAD4)


  1. This 1-wire card uses the DS2450 IC and can measure four separate single ended analog voltage input channels in the range of 0-2.55 or 0-5.10 volts.
  2. Each input has a 249 ohm resistor to common for converting 0-20mA analog current to 0-4.98V.
  3. For digital input operation a dry contact can connect +5V to an input. You can also drive an input with a digital voltage as long as it does not exceed 5.1V.
  4. For higher input impedance you may remove the 249 ohm resistors if not measuring 0-20mA current.
Card Type:
Type Description
1 Input Range 0-5.10V (Use for 4-20 mA current and digital inputs)
4 Input Range 0-2.55V (Alternate voltage input range)

Connector CN2 Pinout:
Pin Numbers Description
1 Jumper selectable for Common or +5V
2 A-D channel 4
3 A-D channel 3
4 A-D channel 2
5 A-D channel 1
6 Jumper selectable for Common or +5V

The "Type" must be 1 or 4 as described above. The "Mode" must always be "Separate power".

Modbus Register Information:
This device has four consecutive Modbus input registers, one for each A-D channel. The conversion from Modbus register value (R) to volts (V) or current in mA (C) is:
Type Voltage Range Modbus Range Conversion
4 0-2.55V 0-1023 V=R/400
1 0-5.10V 0-1023 V=R/200
The raw modbus reading is offset by about 10 counts in the A-D converter. Therefore the range is actually about 10 to 1023. For higher accuracy measurements you should take this offset into account by calibrating with two known input values at the low and high end of your range and calculating conversion coefficients to do an exact calibration from raw counts to required engineering units.

Parameter Specification
Temperature -40 to +85C (-40 to +185F)
Input Impedance 249 ohm or about 1.0M ohm if resistor is removed
Power 0.5 mA
Resolution 10 Bits
Accuracy 8 Bits

Schematic and Parts List:
Reference Part Number
CN1 Digikey 281-1451-ND
CN2 Digikey 281-1452-ND
D1 Dallas Semi DS9503P
D2-D6 Digikey SA5V0ADICT-ND
U1 Dallas Semi DS2450S
R1-R4 Digikey 249KQBK-ND

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