Examples of Digital, Analog and Temperature I/O Devices for use with IOLAN I/O Device Servers

Digital (Discrete) input (applicable for IOLAN (S)DS1 D4 or D2R2)
There are two types of Digital input contact types:
Dry contact type:  No voltage or current is supplied by the I/O device.  The device senses when a pair of contacts are open or closed

  • Open = "0"
  • Close to ground = "1"

Wet contact type:  Voltage applied by the device representat a binary 1 or 0

  • 0v - 3v = "0"
  • 10v - 30v = "1"

Examples of Digital (Discrete) input devices (dry or wet contact type)

  • Selector switches,pushbuttons, thumbwheel switches
  • Photoelectric eyes, limit switches, circuit breakers
  • Proximity switches, level switches
  • Motor starter contacts
  • Relay contacts
  • Fans, lights, horns, valves

Digital (Discrete) Output (applicable for IOLAN (S)DS1 D4 or D2R2)
Digital output exists when a voltage is applied to a pair of digital output leads.  This voltage can be sourced (sinked) by internal or external sources.  In addition, there can be pulse output when the device is active.

Examples of Digital (Discrete) output devices

  • Alarms
  • Control relays
  • Fans, lights, horns, valves
  • Motor starters, solenoids

Relay Output ( applicable for IOLAN (S)DS1 D2R2 or A4R2)
Relay output exists when contacts are closed on a pair of relay leads.

Examples of Relay output devices

  • Alarms
  • Control relays
  • Fans, lights, horns, valves
  • Motor starters, solenoids

Analog Input (applicable for IOLAN (S)DS1 A4 or A4R2)
Analog input exists when variable voltage or current values received from a sensor corresponds to a floating point decimal value.

Examples of Analog input devices

  • Temperature sensors
  • CO2 sensors
  • Pressure sensors
  • Humidity  sensors
  • Flow sensors
  • Potentiometers.

Thermocouple Temperature Sensors (applicable for IOLAN (S)DS T4)
Thermocouple Temperature Sensors are the most popular type of industrial temperature sensor (widely used in the steel industry and heating applicance safety).  They operate by placing two dissimilar metals together causing voltage to vary according to the temperature.  They are relatively inexpesive and operate over a wide temperature range. 

Types of Thermocouple Temperature Sensors

  • Type B – 500 to 1800C
  • Type E – 0 to 1000C
  • Type J  – 0 to 760C
  • Type K – 0 to 1370C
  • Type R – 500 to 1750C
  • Type S – 500 to 1750C
  • Type T –  -100 to 400C

RTD Temperature Sensors (applicable for IOLAN (S)DS T4)
Resistance Temperature Detectors (RTD), also called Resistance thermometers, are temperature sensors that exploit the predictable change in electrical resistance of some materials with changing temperature. As they are almost invariably made of platinum, they are often called platinum resistance thermometers (PRTs). They are slowly replacing the use of thermocouples in many industrial applications below 600 °C.  Resistance thermometers are constructed in a number of forms and offer greater stability, accuracy and repeatability in some cases than thermocouples. While thermocouples use the Seebeck effect to generate a voltage, resistance thermometers use electrical resistance and require a small power source to operate. The resistance ideally varies linearly with temperature.

Examples of RTD Temperature Sensors

  • PT100 - Platinum 100 W at 0 °C  - range of –200C to 400C
  • PT1000 – Platinum 1000 W at 0 °C - range of –40C to 160C
  • Ni 518 – Nickel temp coefficient of .518 - range of –80C to 100C


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