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CM3 RTD Module Concept

Consecutively Changing​


An analog value is a consecutively changing value, such as voltage, current, temperature, velocity, pressure, and flow rate.

For example, a temperature value is consecutively changing with time.
However, as the changing temperature value is directly input into the PLC, its equivalent analog amount of DC voltage (0V ~ +10V) or DC current (4mA ~ 20mA) is input into the PLC via a transducer.

Non-Consecutively Changing​


A constant is a non-consecutively changing value, such as 0, 1, 2, or 3. These values are called digital values.

The digital value 0 represents an OFF signal.
The digital value 1 represents an ON signal.

binary-coded decimal (BCD) and binary values are also considered digital values.

The CPU module is unable to directly input analog values to calculate their corresponding digital values. Therefore, the system converts analog values into digital values and then inputs the digital value into the CPU.

It is necessary to convert the digital value of the CPU into the analog value to output analog values to the external side.

Platinum (PT) and Nickel (Ni) Resistors​

  • There is a sensor to detect temperature as resistance.
  • Platinum100 (PT100) and Japanese Platinum100 (JPT100) resistors display 100.00Ω of output for a temperature of 0°C.
  • A Platinum1000 (PT1000) resistor displays 1,000.00Ω of output for a temperature of 0°C.
  • A Nickel1000 (Ni1000) resistor displays 1,000.0Ω of output for a temperature of 0°C.