Many measurement and monitoring applications in the utility and process industries need a standard AC signal converted into a 4-20mA current output for onwards transmission to a control or telemetry system.
Typical examples include current consumption of AC Drives or to check the current being drawn by pumps which may be under-rated in power terms.
Lee-Dickens’ new APT35L module is suited to this function. It is housed in a DIN-rail package that can be fitted in any convenient location, for example to interface process measurements to a control room or SCADA function. It comes calibrated to accept both 0 to 1A AC signal and a 0 to 5A AC signal – the customer selects which to use by wiring to different points on the instrument’s terminal block.
Accuracy is better than ±0.1% of span for a pure sinusoidal input and with excellent input-output isolation, high surge current capability and high output signal-to-noise ratio the device is immune to ground loop signals and RFI problems as well.
An internal transformer isolates the input from the output enabling the transmitter to withstand large momentary inputs. Site calibration is performed by means of Zero and Span multi-turn potentiometers for fine-tuning. The APT35L is also equipped with a test terminal that enables the user to measure the output current without breaking the current loop. The test terminal gives a voltage output (measured across an internal 10 ohm resistor) proportional to the output current.
The transmitters are housed in polycarbonate plastic enclosures suitable for mounting on DIN rail.
The power requirements are 8 to 32 Volt DC and the unit has a response time constant of 200msec and a Temperature Coefficient of ±0.1% of span/10 degrees C. Operating temperature range is 0 to +50 degrees C.
The APT35L supercedes the ACT-2I in Lee-Dickens’ AlphaPOWER Range.