ACI A/CTA2-50-RMS 4 to 20 mA Output Analog Current Sensor
True RMS measurement computes the actual heating value of the waveform rather than assuming a clean sine wave, so the A/CTA2-50-RMS stays accurate on distorted current. That is what makes it usable downstream of variable frequency drives, switching power supplies, electronic ballasts and SCR controls, where an averaging sensor will read low or high depending on the harmonic content.
Amperage range is field selectable across 0 to 10 / 20 / 50 A, so a single part number covers three spans and stock can be consolidated. Selecting the narrowest range that contains the expected load gives the best resolution, because accuracy is specified as a percentage of the selected range rather than of the maximum.
The output is a 2-wire, loop-powered 4 to 20 mA signal, which needs an external +8.5 to 30 VDC supply. ACI specifies a maximum run of 30 m (98.4 ft) of 2-conductor shielded cable between the sensor and the building management system. Where the controller input expects a voltage signal, ACI publishes 249 Ohm and 499 Ohm precision resistors that convert the loop to 1 to 5 VDC or 2 to 10 VDC at the panel.
The solid-core aperture requires the conductor to be threaded through the sensor, which suits new panel builds and OEM applications where the wiring is not yet terminated.
Specifications on this page are taken from the ACI 4 mA to 20 mA Output Current Sensor Series data sheet Version 2.0 and User's Manual I0000789 Rev. 10.0.
Best For
- Variable frequency drives, switching power supplies, electronic ballasts and SCR loads where the waveform is distorted
- Computer rooms and data centres with non-linear electronic loads
- Load trending and basic power monitoring on single-speed linear loads
- LEED documentation and energy project ROI justification
- Continuous amperage feedback to a BMS, PLC or DDC analog input
- Preventative maintenance programs that need measured current, not just on/off status
Warranty
Key Features
True RMS Measurement
Computes true heating value, so readings stay accurate on distorted waveforms from VFDs, switching supplies, electronic ballasts and SCR loads.
Field-Selectable Ranges
One part number covers 0 to 10 / 20 / 50 A. Pick the narrowest span that contains the expected load for the best resolution.
4 to 20 mA (2-wire, loop powered) Output
Loop-powered 2-wire signal on 2-conductor shielded cable, up to the 30 m (98.4 ft) run ACI specifies. Optional 249 Ohm and 499 Ohm resistors convert to 1 to 5 VDC or 2 to 10 VDC at the panel.
Solid-Core Aperture
Threaded aperture for new construction and OEM panel builds.
Published Accuracy
+/- 1% of selected range. All current output sensors are calibrated at an ambient room temperature of 71 °F (21.5 °C).
Patented DIN Rail Mounting Foot
Snaps onto 35 mm DIN rail for panel installation. U.S. Patent No. 7,416,421.
Technical Specifications
| ACI Item Number | 142373 |
| Core Style | Solid-Core |
| Selectable Amperage Ranges | 0 to 10 / 20 / 50 A |
| Measurement Method | True RMS |
| AC Waveform | Distorted & Pure Sinusoidal |
| Output Signal | 4 to 20 mA (2-wire, loop powered) |
| Accuracy | +/- 1% of selected range |
| Operating Frequency Range | 15 Hz to 100 Hz |
| Response Time | 600 mS (rise time) and 2800 mS (fall time) |
| Monitored Current Type | AC Current |
| Maximum AC Voltage | 600 VAC |
| Isolation Voltage | 2200 VAC |
| Supply Voltage | +8.5 to 30 VDC (reverse polarity protected); 250 Ohm load (1 to 5 VDC): +13.5 to 30 VDC; 500 Ohm load (2 to 10 VDC): +18.5 to 30 VDC |
| Supply Current | 25 mA minimum |
| Maximum Load Resistance @ 24 VDC | 775 Ohms (formula: (24 VDC - 8.5 VDC) / 0.020 A) |
| Output Signal | Maximum Output | 4 to 20 mA (2-wire, loop powered) | limited to 25 mA |
| Aperture Size | 0.75 in (19.05 mm) |
| DIN Rail Size | 35 mm (U.S. Patent No. 7,416,421) |
| Operating Temperature Range | 5 to 104 °F (-15 to 40 °C) |
| Operating Humidity Range | 0 to 95% RH, non-condensing |
| Storage Temperature | RH Range | 41 to 95 °F (5 to 35 °C) | 40 to 85% RH, non-condensing |
| Enclosure Material | Flammability Rating | PC/ABS (polycarbonate / ABS blend) | UL94-V0 |
| Wiring Connections | 2-position screw terminal block (polarity sensitive) |
| Wire Recommendations | 2-conductor shielded cable |
| Wire Size | 18 to 24 AWG (0.823 mm2 to 0.205 mm2), copper wires only |
| Terminal Block Torque Rating | 4.43 to 5.31 in-lbs (0.5 to 0.6 Nm) |
| Minimum Mounting Distance | 1 in (2.6 cm) from relays, contactors and transformers |
| Calibration Reference | All current output sensors are calibrated at an ambient room temperature of 71 °F (21.5 °C) |
| Agency Approvals | UL/CUL US Listed (UL 508) Industrial Control Equipment, File # E309723, RoHS2, WEEE, UKCA; -RMS versions CE to IEC 61326-1:2012 Class A |
| Product Dimensions (L x W x H) | 2.760 in (70.11 mm) x 3.343 in (84.92 mm) x 1.050 in (26.67 mm) |
| Product Weight | 0.190 lbs (0.087 kg) |
| Warranty | Five (5) Year Limited Warranty |
Not intended for use in life / safety applications or in hazardous / classified locations.
Range Selection and Commissioning
All models with selectable amperage ranges ship with the range selection jumper factory set on the high range; set the jumper to the correct range at commissioning. The selected range is the maximum current that may be applied to the monitored conductor and must not be exceeded. An extra jumper shunt is supplied and may be discarded if not needed; in high-vibration installations ACI recommends using the jumper shunt without the tab.
Output Conversion Resistors (ordered separately)
| ACI Item # | Description |
|---|---|
| 100307 | 249 Ohm, 1/4 W, +/- 1% tolerance, 50 ppm resistor (converts output to 1 to 5 VDC) |
| 100306 | 249 Ohm, 1/4 W, +/- 0.1% tolerance, 50 ppm resistor, recommended for best accuracy (converts output to 1 to 5 VDC) |
| 100469 | 499 Ohm, 1 W, +/- 1% tolerance, 50 ppm resistor (converts output to 2 to 10 VDC) |
Documentation
ACI 4 mA to 20 mA Output Current Sensor Series Data Sheet (Version 2.0)ACI 4 mA to 20 mA Output Current Sensor Series User's Manual (I0000789 Rev. 10.0)Related Products
Frequently Asked Questions
What output signal does the ACI A/CTA2-50-RMS produce?
The A/CTA2-50-RMS produces a 4 to 20 mA (2-wire, loop powered) signal. It is loop powered and needs an external +8.5 to 30 VDC supply.
What amperage ranges does the ACI A/CTA2-50-RMS cover?
The A/CTA2-50-RMS covers 0 to 10 / 20 / 50 A, selectable in the field. Accuracy is specified as a percentage of the selected range, so choosing the narrowest range that contains the expected load gives the best resolution.
Can the ACI A/CTA2-50-RMS be used downstream of a variable frequency drive?
Yes. True RMS measurement computes the actual heating value of the waveform, so the sensor remains accurate on the distorted current produced by VFDs, switching power supplies, electronic ballasts and SCR controls.
What is the published accuracy of the ACI A/CTA2-50-RMS?
+/- 1% of selected range. All ACI current output sensors are calibrated at an ambient room temperature of 71 °F (21.5 °C).
How is the ACI A/CTA2-50-RMS converted to a voltage signal?
ACI publishes precision resistors for this: item # 100307 or # 100306 (249 Ohm) convert the loop to 1 to 5 VDC, and item # 100469 (499 Ohm, 1 W) converts it to 2 to 10 VDC. The resistor is ordered separately and installed at the controller input.
ACI Five (5) Year Limited Warranty. This product is covered by Automation Components, Inc.’s Five (5) Year Limited Warranty, published in the front of the ACI Sensors & Transmitters catalog and on the ACI website. Warranty terms are set by the manufacturer and are subject to change without notice.
- Mounting Type:
- Solid-Core
- Selectable Range:
- 0-10/20/50A
- Output Signal:
- 4-20 mA
- Measurement:
- True RMS
- AC Waveform:
- Distorted and Pure Sinusoidal
- Sensor Power:
- Loop Powered
- Warranty:
- 5-Year Limited
