True-rms ammeters promise accurate reading

From Murata Power Solutions comes the Datel ACA5-20RM series of functionally complete, high current, true-rms responding AC ammeters designed to interface directly with an external 5A output current transformer (CT). Covering input ranges from 100A to 500A, the ACA5-20RM series is suitable for use in electronic equipment that uses switching power supplies such as inverters and generators, battery chargers, power distribution units and AC/DC power supplies.

True-rms responding ammeters provide accurate and reliable performance in switching power supply applications where input currents are typically distorted and do not resemble the universally recognized sine-wave shape. Other approaches to measurement such as average responding AC ammeters can result in reading errors in excess of 20 percent of their full-scale output. In critical applications, this may lead to inadvertent overloading of circuit breakers or fuses, which in turn can cause costly power outages.

The ACA5-20RM family scales and displays the output of 5A 'donut' style CTs. The series covers three ranges: 100A, 200A and 500A. A choice of 85- to 140Vac or 170- to 264Vac (at 47 to 63Hz) operating supply voltages is offered for each range. Maximum power consumption is less than 50mA and operating temperature range is 0°C to +60°C.

Crest factors for the ACA5-20RM series are as high as five and all models specify 2000V isolation between the AC power source and the external 5A CT. The complete design uses a reliable single-board construction, has a built-in low-burden toroid sensor and a bright red LED display with 9.4mm high characters. Where specific applications require, Murata can supply 100:5, 200:5 and 500:5 accessory CTs.

Pricing for ACA5-20RM ammeters is $94 for singles and drops to $79.90 at 100 pieces. Small quantities (less than ten) are available from stock, while OEM quantities are 12 weeks ARO.