DC Input Isolator, Signal Splitter - Q404-4

Application

DC input four-wire transmitters are used to isolate and convert DC voltage or current signals into proportional, standard industrial control signals such as 4-20mAor 0-10V. Typically an industrial control system such as a DCS or PLC requires standard industrial control signals with full isolation to ensure reliable, strong signals.

In most industrial process control or data acquisition applications, several different input sources, including voltages and currents from various field instruments (e.g. level, flow, pressure and position sensors), are common. Four-wire transmitters accept these field inputs and provide the controller (DCS & PLC) the standard industrial signals they require. The four-wire transmitter will increase the signal drive to high impedance loads and may improve resolution of the process variable.

The 2000VAC isolation capability of the Q404 prevents ground loops from causing errors in DC voltage and current signals and may reduce susceptibility to Electro Magnetic Interference (EMI) and Radio Frequency Interference (RFI). Isolation also provides protection from high voltages and current spikes which may damage expensive Supervisory Control And Data Acquisition (SCADA) equipment.

Operation

The ActionI/Q model Q404 operates as a fourwire transmitter; each channel derives its power from an independent, transformer isolated, DC to DC power source (10.8 to 26.4VDC). Typically a 12 or 24VDC source is used for power.

The Q404 has fixed input and output ranges. Standard input and output ranges in Table 1 are calibrated to rated accuracy. Units are configured for one range per module and one or two channels per module.

Note: To maximize accuracy and thermal stability, final calibration should be performed with the intended output load and the unit should be mounted in the operating installation, allowing at least 1 hour for warm up and thermal equilibrium of the system.

Calibration

1. To check calibration, connect the input to a calibrated DC source. Connect the output to a DC voltage or current meter and the input power to DC source (10.8 to 26.4VDC) capable of providing up to 0.5 Amps.
2. Set the calibrator to the specified minimum DC input value and adjust the zero potentiometer for minimum (e.g. 4mA) output.
3. Set the calibrator to the specified maximum DC input value and adjust the span potentiometer for maximum (e.g. 20mA) output.
4. Repeat steps 2 and 3 to validate calibration to the output load.

TECHNICAL SPECIFICATION (Q404-4)