XYTRONIC THREE-PHASE REFERENCE STANDARDS

RX-30, RX-31 & RX-33
Reference Standards

The RX-30, RX-31, and RX-33 by Radian Research are industry-leading energy reference standards designed for exceptional accuracy, precision, and stability in meter testing and calibration applications offering ±0.04%, ±0.02%, and ±0.01% accuracy respectively.

Engineered to provide NIST-traceable, high-precision measurements, these reference standards are essential for utilities, meter manufacturers, and calibration laboratories that demand the highest level of measurement confidence and compliance.

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Product Highlights

The RX-30, RX-31, and RX-33 represent the pinnacle of energy measurement accuracy, precision, and stability. Engineered for demanding metrology applications, the RX-33 provides industry-leading 0.01% accuracy, long-term measurement stability, and full NIST-traceability, making it ideal for meter test systems, calibration labs, and standards laboratories.

With support for both single-phase and polyphase configurations, advanced measurement capabilities, and seamless integration with WECO test equipment, the RX-30, RX-31, and RX-33 ensure unmatched performance and confidence in every test. Built with RADIAN’s legacy of excellence, they set the standard for reliable and repeatable energy measurement.

Precision Perfected with RADIAN

RADIAN RX-30

The RADIAN RX-30 provides ±0.04% energy accuracy (±0.02% at unity power factor), making it a dependable choice for meter testing, calibration, and precision measurement work. It supports wide voltage, current, power, and frequency ranges while maintaining consistent performance across typical utility and laboratory environments.

Voltage accuracy is ±0.02% and direct AC current accuracy is ±0.028% at TCAL. Power accuracy matches the energy class at ±0.04%. Long-term drift is managed by a stability specification of 0.0016% × √month, and the energy temperature coefficient is 0.0005%/°C, supporting predictable results as conditions change.

Performance Highlights

• Power and energy accuracy: ±0.04% (±0.02% at unity PF)

• Voltage accuracy: ±0.02%

• Current accuracy: ±0.028%

• Stability: 0.0016% × √month

• Energy temperature coefficient: 0.0005%/°C

A front and back image of the RADIAN RX-30 on a semi-transparent background.

RADIAN RX-31

The RADIAN RX-31 delivers ±0.02% energy accuracy (±0.01% at unity power factor), a reduced uncertainty class compared to the RX-30. The same accuracy applies to its power measurements, supporting applications that require tighter uncertainty budgets and higher traceability.

Voltage accuracy is ±0.01% and direct AC current accuracy is ±0.014% at TCAL. A stability specification of 0.0004% × √month gives improved control over drift, and the energy temperature coefficient remains 0.0005%/°C.

Performance Highlights

• Power and energy accuracy: ±0.02% (±0.01% at unity PF)

• Voltage accuracy: ±0.01%

• Current accuracy: ±0.014%

• Stability: 0.0004% × √month

• Energy temperature coefficient: 0.0005%/°C

The RADIAN RX-31 on a semi-transparent background.

RADIAN RX-33

The RADIAN RX-33 provides ±0.01% energy accuracy (±0.005% at unity power factor), the highest accuracy class in the RX-30 series. It supports advanced calibration laboratories, metrology centers, and manufacturing environments where minimized uncertainty and maximum traceability are essential.

Voltage accuracy is ±0.005% and direct AC current accuracy is ±0.007% at TCAL. Power accuracy matches the energy class at ±0.01%. Long-term drift is controlled by a stability specification of 0.0004% × √month for both power and energy, and the energy temperature coefficient is 0.0005%/°C.

Performance Highlights

• Power and energy accuracy: ±0.01% (±0.005% at unity PF)

• Voltage accuracy: ±0.005%

• Current accuracy: ±0.007%

• Stability: 0.0004% × √month

• Energy temperature coefficient: 0.0005%/°C

The RADIAN RX-33 on a semi-transparent background.

The RADIAN RX-30 transposed over grabs of readings from the equipment.

Features

Accuracy, Precision, & Stability with the RX-30, RX-31, & RX-33

Ultra-High Accuracy – Industry-leading energy measurement precision with long-term stability and reliability.
Single-Phase & Polyphase Compatibility – Supports meter testing, calibration, and power quality analysis.
Multiple Accuracy Classes – Available in ±0.04%, ±0.02%, and ±0.01% accuracy levels to match specific testing needs.
Advanced Measurement Capabilities – Measures voltage, current, power, phase angle, harmonics, and power factor with unmatched consistency.
Seamless Integration – Works with WECO Meter Test Systems and other calibration equipment for comprehensive testing.
Durable & Reliable – Designed for long-term operational stability and minimal maintenance.
Backed by ISO/IEC 17025 accreditation for industry-leading measurement uncertainties and unmatched customer trust for over 35 years.

The control panel map on the back the RADIAN three phase reference standards.

Exceptional Accuracy, Precision, and Stability

Built to Connect

Communications: RS-232 with RADIAN legacy RD commands, and Ethernet with SCPI commands.
Programming guide: the application note Controlling RADIAN RX Reference Standards with SCPI, with command scripts and a Python example for automated test systems.
Programmable pulse outputs for Wh, VARh or VAh, plus a bidirectional pulse/frequency comparator port.
Reference clock input (10 or 20 MHz) and an optical sensor port.
Storage: 2 GB internal memory, plus SD card (up to 32 GB) and USB.
Display: a built-in 4.3-inch color touch screen, with an optional external touch screen display.

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Which RX Standard Is Right for You?

All three RX models share the same three-phase platform, functions and connections. They differ in accuracy class and operating environment. For a single-phase primary transfer standard in the lab, see the RADIAN RD-22.

Model	Energy accuracy	Operating temperature	Best for
RADIAN RX-30	±0.04%	-20 to 65 °C	Meter testing and calibration in the shop or field
RADIAN RX-31	±0.02%	-20 to 65 °C	Meter shops and calibration work that need tighter uncertainty
RADIAN RX-33	±0.01%	0 to 40 °C	Calibration labs, metrology centers and manufacturing

Energy accuracy is at 0.5 power factor.

Technical Specifications

Accuracy

	RX-30	RX-31	RX-33
Power and energy, 0.5 lag to 1 to 0.5 lead	±0.04%	±0.02%	±0.01%
Power and energy at unity power factor	±0.02%	±0.01%	±0.005%
Power and energy, 5 mA to <20 mA	±0.08%	±0.04%	±0.02%
Voltage, 30 V to 600 V (525 V at 50 Hz)	±0.02%	±0.01%	±0.005%
Current, 20 mA to 200 A	±0.028%	±0.014%	±0.007%
Current, 5 mA to <20 mA	±0.056%	±0.028%	±0.014%
Phase angle	0.008°	0.005°	0.003°
Repeatability	0.0001% ÷ √(test time in seconds)	0.0001% ÷ √(test time in seconds)	0.0001% ÷ √(test time in seconds)

Accuracy is stated in percent of reading, not percent of scale. Repeatability is already included in the accuracy figures. Power and energy accuracy applies to tests of 1 second or longer.

Stability and Temperature

	RX-30	RX-31	RX-33
Stability, power and energy (× √month)	0.0016%	0.0008%	0.0004%
Stability, voltage (× √month)	0.0008%	0.0004%	0.0002%
Stability, current (× √month)	0.0012%	0.0006%	0.0003%
Temperature drift, power and energy	0.0005%/°C	0.0005%/°C	0.0005%/°C
Temperature drift, voltage	0.00015%/°C	0.00015%/°C	0.00015%/°C
Temperature drift, current	0.0003%/°C	0.0003%/°C	0.0003%/°C
Specified temperature range	−20 to +65 °C	−20 to +65 °C	0 to +40 °C
Operating temperature range	−20 to +65 °C	−20 to +65 °C	−20 to +65 °C
Storage temperature	−40 to +80 °C	−40 to +80 °C	−40 to +80 °C
Relative humidity	95% non-condensing	95% non-condensing	95% non-condensing

Harmonics and Measurement

	RX-30, RX-31, and RX-33
Measurement bandwidth	3,840 Hz (to the 64th harmonic at 60 Hz)
Fundamental frequency	45 Hz to 75 Hz
Sampling	20-bit, 1 million samples per second
Measurement modes	Broadband (all harmonics) or fundamental only
VAR methods	All ANSI and IEC VAR algorithms
Metrics	Watts, Wh, VA, VAh, VAR, VARh, totalized values, volts, amps, phase angle, power factor, and frequency
Voltage input	30 V to 600 V, 1 MΩ input impedance
Current input	1 mA to 200 A on one range, so there is no range switching across the full span; input impedance less than 500 µΩ

Automation and Interfaces

	RX-30, RX-31, and RX-33
Integration time	0.5 seconds by default, adjustable in 0.5-second steps in PCSuite. Integration time is how long each reading is measured; it is separate from the test time.
Ethernet	1 port, SCPI commands (see the SCPI application note)
RS-232	1 port, RADIAN legacy RD commands
USB	2 ports
Pulse outputs	4 programmable bidirectional ports, up to 4 MHz
Reference clock input	10 MHz or 20 MHz
Warm-up	Less than 60 seconds

Physical, Safety, and Calibration

	RX-30, RX-31, and RX-33
Power supply	100 V to 240 V, 50 Hz or 60 Hz, about 35 VA
Dimensions (D × W × H)	190 × 394 × 114 mm
Weight	6.8 kg (15 lb)
Maximum altitude	2,000 m
Enclosure	IP30
Conformity	CE; protection class I (EN 61140)
Overvoltage category	CAT IV 600 V, voltage and current measurement
Recommended calibration interval	1 year
Calibration	NIST-traceable; ISO/IEC 17025 accredited calibration with stated uncertainties available
ISO/IEC 17025 calibration uncertainty	Voltage ±0.003%; current ±0.005%; power and energy ±0.005%; frequency ±0.000005%
Documents	Sample calibration reports: RX-30: ISO/IEC 17025 · ANSI/NCSL Z540-1 RX-31: ISO/IEC 17025 · ANSI/NCSL Z540-1 RX-33: ISO/IEC 17025 · ANSI/NCSL Z540-1 ISO/IEC 17025 scope of accreditation
Brochures	RX-30/RX-31 Brochure and RX-33 Brochure

Accuracy

	RX-30	RX-31	RX-33
Power and energy, 0.5 lag to 1 to 0.5 lead	±0.04%	±0.02%	±0.01%
Power and energy at unity power factor	±0.02%	±0.01%	±0.005%
Power and energy, 5 mA to <20 mA	±0.08%	±0.04%	±0.02%
Voltage, 30 V to 600 V (525 V at 50 Hz)	±0.02%	±0.01%	±0.005%
Current, 20 mA to 200 A	±0.028%	±0.014%	±0.007%
Current, 5 mA to <20 mA	±0.056%	±0.028%	±0.014%
Phase angle	0.008°	0.005°	0.003°
Repeatability	0.0001% ÷ √(test time in seconds)	0.0001% ÷ √(test time in seconds)	0.0001% ÷ √(test time in seconds)

Accuracy is stated in percent of reading, not percent of scale. Repeatability is already included in the accuracy figures. Power and energy accuracy applies to tests of 1 second or longer.

Stability and Temperature

	RX-30	RX-31	RX-33
Stability, power and energy (× √month)	0.0016%	0.0008%	0.0004%
Stability, voltage (× √month)	0.0008%	0.0004%	0.0002%
Stability, current (× √month)	0.0012%	0.0006%	0.0003%
Temperature drift, power and energy	0.0005%/°C	0.0005%/°C	0.0005%/°C
Temperature drift, voltage	0.00015%/°C	0.00015%/°C	0.00015%/°C
Temperature drift, current	0.0003%/°C	0.0003%/°C	0.0003%/°C
Specified temperature range	−20 to +65 °C	−20 to +65 °C	0 to +40 °C
Operating temperature range	−20 to +65 °C	−20 to +65 °C	−20 to +65 °C
Storage temperature	−40 to +80 °C	−40 to +80 °C	−40 to +80 °C
Relative humidity	95% non-condensing	95% non-condensing	95% non-condensing

Harmonics and Measurement

	RX-30, RX-31, and RX-33
Measurement bandwidth	3,840 Hz (to the 64th harmonic at 60 Hz)
Fundamental frequency	45 Hz to 75 Hz
Sampling	20-bit, 1 million samples per second
Measurement modes	Broadband (all harmonics) or fundamental only
VAR methods	All ANSI and IEC VAR algorithms
Metrics	Watts, Wh, VA, VAh, VAR, VARh, totalized values, volts, amps, phase angle, power factor, and frequency
Voltage input	30 V to 600 V, 1 MΩ input impedance
Current input	1 mA to 200 A on one range, so there is no range switching across the full span; input impedance less than 500 µΩ

Automation and Interfaces

	RX-30, RX-31, and RX-33
Integration time	0.5 seconds by default, adjustable in 0.5-second steps in PCSuite. Integration time is how long each reading is measured; it is separate from the test time.
Ethernet	1 port, SCPI commands (see the SCPI application note)
RS-232	1 port, RADIAN legacy RD commands
USB	2 ports
Pulse outputs	4 programmable bidirectional ports, up to 4 MHz
Reference clock input	10 MHz or 20 MHz
Warm-up	Less than 60 seconds

Physical, Safety, and Calibration

	RX-30, RX-31, and RX-33
Power supply	100 V to 240 V, 50 Hz or 60 Hz, about 35 VA
Dimensions (D × W × H)	190 × 394 × 114 mm
Weight	6.8 kg (15 lb)
Maximum altitude	2,000 m
Enclosure	IP30
Conformity	CE; protection class I (EN 61140)
Overvoltage category	CAT IV 600 V, voltage and current measurement
Recommended calibration interval	1 year
Calibration	NIST-traceable; ISO/IEC 17025 accredited calibration with stated uncertainties available
ISO/IEC 17025 calibration uncertainty	Voltage ±0.003%; current ±0.005%; power and energy ±0.005%; frequency ±0.000005%
Documents	Sample calibration reports: RX-30: ISO/IEC 17025 · ANSI/NCSL Z540-1 RX-31: ISO/IEC 17025 · ANSI/NCSL Z540-1 RX-33: ISO/IEC 17025 · ANSI/NCSL Z540-1 ISO/IEC 17025 scope of accreditation
Brochures	RX-30/RX-31 Brochure and RX-33 Brochure

RX Reference Standards FAQ

What is the RX operating range?

30 to 600 V potential and 20 mA to 200 A direct current, three-phase. Optional current cable sets are rated for 120 A (RX-120CK3) or 200 A (RX-200CK3).

The RX-30, RX-31, and RX-33 in ascending order on a transparent background.

What does an RX standard measure?

Watts and watt-hours, volts, amps, VARs and VAR-hours, VA and VA-hours, phase angle, power factor and frequency, plus volt-hours, amp-hours, V²h and A²h, with minimum, maximum and average readings.

How does an RX standard connect to a test system?

Over RS-232 with RADIAN legacy RD commands or Ethernet with SCPI, and through programmable pulse outputs. RX standards work with WECO meter test boards, and the RADIAN RM-111 can compare them against other standards or meters.

Can I use an RX standard in the field?

The RX-30 and RX-31 operate from -20 to 65 °C with CAT IV 600 V safety ratings, so they suit field and shop work. The RX-33 is rated CAT II 600 V and specified from 0 to 40 °C, which fits the lab. All three weigh about 15 lb and run on 24 VDC or a 100–240 VAC converter.

How often should an RX standard be recalibrated?

The recommended calibration interval is one year. RADIAN Calibration Services recalibrates RX standards in our ISO/IEC 17025-accredited lab, with results traceable to NIST.

A young woman using a RADIAN DC reference standard on a WECO 4330X as a part of RADIAN Calibration Services.

Accessories

Whether you need a cost-effective solution for routine testing or the highest level of accuracy for laboratory-grade calibration, these models deliver unmatched reliability and performance.