The card provides 16 inputs, which can be configured by jumpers to measure voltage (0 – 10V), current (0- 20mA) or resistance (PTC and NTC thermistors) in 2 ranges so as to give maximum accuracy. For reading digital signals, thresholds are set and can be adjusted over the Modbus network. Inputs can provide accurate pulse-counting and frequency calculation of a varying signal. Each input has an LED that can be set over the Modbus network to display the status of the digital and analogue inputs.
The card is communicated with by Modbus over a two-wire RS-485 network. The data format is 8bit RTU, with a choice of address, baud-rates and message formats configured by dip switches (see Section 1.3). A software set-up tool is also available for commissioning the cards via a supervisor port in the absence of the master controller and Modbus network.
The input values can be read directly out of the card by selecting one of 34 pre-installed profiles via the Modbus register. These profiles cover all the common current, voltage and thermistor types (see Section 2.3 and Appendices A & C).
The card must be powered off a 24VDC power supply. The inputs are protected against static discharge, but normal static precautions should be taken when handling the cards.