Application #5: Operating logarithmic transducers

Łukasz Smolnicki
Add to MyDirectIndustry favorites

An interesting example of using the MultiCon controller equipped with transducers of non-linear characteristics.

This example is applicable in a process where, for instance, pressure is measured over a very wide range, and where high accuracy is required at low values. The above function is well implemented by a pressure sensor with logarithmic characteristic.

The application features the CMC-99-PS42/E/R45/IO4/UN3-0B1 model.

Signal inputs:

The UN3 module consists of 3 insulated, universal inputs (U / I / RTD / TC / mV). Each of them is connected to an output signal coming from a pressure transducer of logarithmic characteristics.

The IO4 module consists of 4 current outputs, three of which send the calculated pressure value to other elements of the control system, where the value is represented in the linear form already.

The R45 module consists of 4 relay outputs with a load capacity of 5A, used for controlling the main valves.


The recorded data is downloaded by connecting a portable memory device to the USB port.


Signals from pressure transducers are sent to the CMC-99, where, according to the introduced mathematical formula, the logarithmic 4-20 mA signal is converted into pressure linear readings. These values get recorded and form the basis for controlling proportional and shut-off valves.

Special features:

For convenient operating a USB port is provided on the front of the device.

Application #5: Operating logarithmic transducers

Associated Trend items