Stand-alone solution for calibrating meters, clamp meters and current transformers

29 October 2013

The Yokogawa 2558A is a new compact bench AC voltage/current unit that is said to offer a simple stand-alone solution for the calibration of measuring instruments and power sensing devices including power meters, clamp meters and current transformers.

The unit is said to offer high accuracy - 0.04% on AC voltage and 0.05% on AC current - and a choice of output ranges from 1.00 mV to 1200.0 V AC and 1.00 mA to 60.00 A AC (expandable to 120 A by using two units in parallel).

Operation is via front-panel rotary dials and switches for each function and each digit of the 4½-digit display. A sweep function, output divider and internal phase shifter are incorporated, and a range of computer interfaces allows the 2558A to be incorporated into an automatic test system in a production environment.

The instrument operates over a frequency range of between 40 and 1000 Hz with a frequency accuracy of ±50 ppm, including the provision of fixed frequencies of 50/60 Hz (commercial) and 400 Hz (marine and aviation).

Multiple 2558As can be synchronised using the internal phase shifter, allowing two instruments to be used as accurate sources of voltage and current for calibrating power meters. An output divider enables linearity tests to be carried out efficiently.

Dials and switches are provided for each digit and function, and traditional seven-segment LEDs provide visibility. When the deviation dials are adjusted to check the full scale value on the meter, the deviation from the main output setting is displayed as a percentage of full scale.

Typical users of the system will include calibration laboratories, suppliers of panel meters, indicating instruments, analogue testers, clamp meters, protection relays and current and power transducers.

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