2558A Precision AC Standard
AC Voltage / Current – 50 A ("75A") Max. output current

Simple standalone solution for calibrating meters, clamps and CTs
High Accuracy 0.05% AC Current and 0.04% AC Voltage, Wide Output Range from 1.00 mA to 60.00 A and 1.00 mV to 1200.0 V

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  • Intuitive operation
    Dials and switches are provided for each digit and function, and traditional 7-segment LEDs provide clear visibility
  • 6 voltage ranges (100 m/1/10/100/300/1000 ([V])
    4 current ranges (100 m/1/10/50 ([A])
  • Sweep (Voltage/Current/Frequency)
  • Output Divider
    Linearity tests can be simply performed by dividing the output into steps. For example, a setting of 4 will generate steps of 25, 50, 75 and 100% of the set output value.
  • % Deviation readout
  • Common current output terminals
    The same output terminals are used for all current ranges. Test times are therefore reduced by avoiding the need to change the wiring for meters which have different ranges.
  • Wide frequency range-: 40 to 1000 Hz (Frequency accuracy : ±50 ppm)


  • Calibration and inspection of measuring instruments and meters
  • Calibration agencies and company standards laboratories
  • Developers and manufacturers of indicating instruments, clamp-on testers, electric relays, and CTs
  • OEM Applications


The 2558A precision DC calibrator is an easy-to-use, yet highly accurate instrument that can be used to calibrate analog power meters, thermometers, and temperature controllers that use a thermocouple or a resistance temperature detector (RTD).

The 2558A can output a wide range of AC voltages (1.00 mV to 1200.0 V) and currents (1.00 mA to 60.00 A) at frequencies of 40 to 1000 Hz. The accuracy (maximum error) is ±0.04% for AC voltage and ±0.05% for AC current, ensuring accurate calibration, and the stability is as high as ±0.005%/h. The easy-to-read digital display and dials for setting each digit are intuitive to use. The current output terminals can be used for all measurement ranges, which improves work efficiency by eliminating the need to change cables for a specific current level.

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The wide output ranges of 1.00 mV to 1200.0 V AC and 1.00 mA to 60.00 A AC mean that the 2558A is the instrument of choice for the cost effective calibration of AC analog meters. Rotary controls and a range of computer interfaces enable the 2558A to be intuitively operated through the front panel or controlled by and ATE system.

  • Literature
  • Specifications
Literature and Technical Information
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AC Voltage / Current Standards

++ Yokogawa 2558A AC Standard Specification Brochure | 3.4 MB
Model: Yokogawa 2558A AC Voltage / Current Standards
Frequency range
Accuracy (internal): ± 50 ppm (180 days)
± 100 ppm (1 year)
Mode: Internal / External / FREQUENCY METER
Internal: 50 / 60 / 400 Hz
VAR (40 to 1000 Hz, 0.001 Hz resolution)
External: EXT1 / EXT2 (Use the terminals for the synchronized operation)
Frequency Meter: MIN/MAX
Range: 20 to 1000 Hz
Resolution: 0.001 Hz
  Sweep, output divider and deviation functions are used for the frequency
Target: Voltage / Current / Frequency
Speed: Approx. 16/32/64 sec. selectable during 0 to 100%, 100 to 0% of setting
Output divider
Target: Voltage / Current / Frequency
Denominator: m 4 to 15
Numerator: n 0 to 15 (n ≤ m)
Target: Voltage / Current / Frequency
Variable range: Two dials
Resolution of the first dial : 0.2% of the main setting
Resolution of the second dial : 0.01% of the main setting
Operation: Two dials
Resolution of the first dial : 0.2% of the main setting
Resolution of the second dial : 0.01% of the main setting
Deviation preset: OFF / 0 / 2% / 5%
Output terminal
Voltage: Plug-in terminal (safety terminal)
Current: Large binding post
Selectable LO terminal to earth or floating. Max. floating voltage to earth : 12 Vpk
Main setting: 5 digits LED
Output Divider: 2 digits LED (mm and m)
Deviation: 4 digits LED
Output: 5 digits LED
Frequency/Phase 6 digits LED
External I/O
Sync. Terminals (two input terminals and two output terminals)
I/O voltage: 3±0.1 Vrms, 2 phase sine wave
Frequency: 40 to 1000 Hz
Input resistance: Approx. 1 MΩ
Output resistance: Approx. 50 Ω
USB PC interface (for PC connection)
Connector: Type B connector (receptacle
Electrical and mechanical specifications: Complies with USB Rev. 2.0
Supported transfer modes: High Speed, Full Speed
Ethernet interface
Connector: RJ-45 connector
Electrical and mechanical specifications: Confirms to the IEEE 802.3
Transmission methods: 100 BASE-TX / 10 BASE-T
GP-IB interface
Electrical and mechanical specifications; Complies with IEEE St’d 488-1978
Functional specifications: SH1, AH1, T6, L4, SR1, RL1, PP0, DC1, DT1, C0
Address: 0 to 30
Warm-up time: Approx. 30 minutes
Power Voltage: 100 to 120 VAC / 200 to 240 VAC / 50/60 Hz
Power Consumption: 200 VA
Power supply voltage fluctuation range: 90 to 132 VAC / 180 to 264VAC / 48 to 63 Hz
Temperature Range: 5 to 40°C
Storage Temperature: -15 to 60°C
Humidity Range: 20 to 80%RH (no condensation)
Dimensions: 426(W) x 132(H) x 400(D) mm
Weight: Approx. 20 kg