Product Highlights
The RD-22 Ultra Stable is a variant of the RADIAN RD-22 primary transfer standard. Instead of covering a wide range, it is optimized for the points most labs use to carry traceability: 120 V and 240 V at 5 A. A potential transformer and range switching designed for 120/240 V operation, plus a current comparator with a fixed winding around the core, give it ±0.002% (20 ppm) energy accuracy and a transfer uncertainty of 0.0002% (2 ppm) within five days and 0.5 °C.
It transfers accurate, traceable measurements from the RADIAN calibration laboratory into your lab, or it can be calibrated directly by a national metrology institute such as NIST.
In a stable test environment, a 10-second test repeats within ±0.6 µWh/VAh at 120 V and 240 V at 5 A, with a 95% confidence interval. Typical experimental repeatability is below ±0.25 µWh/VAh. Over five days, reproducibility is ±2 µWh/VAh at the same points, also at 95% confidence.
The Ultra Stable keeps the low temperature coefficients of the RD-22, typically below 0.0002%/K (2 ppm/K). Each calibration report lists the temperature coefficients for twelve cardinal test points, so your uncertainty budget is built on measured values rather than assumptions.
Features
- Power and energy accuracy: ±0.002% (20 ppm)
- Optimized operating points: 120 V and 240 V (±15%) at 5 A (±15%)
- Transfer uncertainty: 0.0002% (2 ppm), within five days and 0.5 °C
- 10-second repeatability: ±0.6 µWh/VAh at 95% confidence (typical below ±0.25 µWh/VAh)
- Five-day reproducibility: ±2 µWh/VAh at 95% confidence
- Temperature coefficients typically below 0.0002%/K (2 ppm/K), reported for twelve cardinal test points
- NIST-traceable calibration from RADIAN, with ISO/IEC 17025-accredited calibration available
What Makes the RD-22 Ultra Stable Different
- Optimized potential input. A newly designed potential transformer and range switching built for 120/240 V operation.
- Fixed-winding current comparator. The electronically compensated concentric core current comparator uses a fixed winding around the core to improve repeatability and reproducibility on the current input.
- Non-galvanic current connection. Current is measured through the comparator rather than a direct electrical connection.
- Isolated auxiliary power. An external converter supplies 24 VDC to the standard, minimizing 50/60 Hz line interference in the measurement circuitry.
- Software-only calibration. No physical adjustments; all calibration is performed in software.
RD-22 or RD-22 Ultra Stable: Which Fits Your Lab?
Both are single-phase primary transfer standards on the same platform. The difference is range versus stability. The RADIAN RD-22 autoranges across a wide range of voltage and current. The RD-22 Ultra Stable is optimized for 120 V and 240 V at 5 A, where it delivers lower uncertainty.
Either one can carry traceability to a RADIAN RS-933 sourcing standard in your lab. Not sure which fits your program? Our team can help you compare them against your test points and uncertainty goals.
| RADIAN RD-22 | RD-22 Ultra Stable | |
|---|---|---|
| Model | RD-22-332 | RD-22-332S |
| Energy accuracy | ±0.005% (50 ppm) | ±0.002% (20 ppm) |
| Voltage | 40 to 600 V, autoranging |
120 V or 240 V ±15% (60 to 276 V operational) |
| Current | 0.2 to 125 A or 0.2 to 200 A, autoranging |
5 A ±15% (1.25 to 10 A operational) |
| Frequency | 45 to 65 Hz | 45 to 65 Hz |
| Temperature | 23 °C ±2 °C (18 to 30 °C extended) |
23 °C ±2 °C (18 to 30 °C operational) |
| Recalibration | 365 days | 365 days |
| Best for | A primary transfer standard across a wide range |
The lowest uncertainty at 120/240 V and 5 A |
Technical Specifications
Accuracy
| RD-22 Ultra Stable | |
|---|---|
| Power and energy | ±0.002% (20 ppm) at 120 V or 240 V and 5 A |
| Transfer uncertainty | 0.0002% (2 ppm), within five days and 0.5 °C |
| Repeatability, 10-second test | ±0.6 µWh/VAh at 120 V and 240 V, 5 A, 95% confidence (typically below ±0.25 µWh/VAh) |
| Reproducibility, five days | ±2 µWh/VAh at the same points, 95% confidence |
Accuracy is stated in percent of reading, not percent of scale.
Stability and Temperature
| RD-22 Ultra Stable | |
|---|---|
| Temperature coefficients | Typically below 0.0002%/K (2 ppm/K), measured and reported for twelve cardinal test points on each calibration report |
| Ultra Stable temperature range | 23 °C ±2 °C |
| Operational temperature range | 18 °C to 30 °C |
| Ultra Stable humidity range | 30% to 65% relative humidity |
| Operational humidity range | 0% to 95%, non-condensing |
| Warm-up | 60 minutes |
Harmonics and Measurement
| RD-22 Ultra Stable | |
|---|---|
| Harmonic analysis (option) | Same as the RD-22: to the 50th harmonic; accuracy ±0.030% for the 1st to 23rd and ±0.075% for the 24th to 50th |
| Frequency | 45 Hz to 65 Hz |
| Phase angle range | 0° to 360° |
| Voltage input | Ultra Stable range: 120 V ±15% (102 V to 138 V) or 240 V ±15% (204 V to 276 V); operational range 60 V to 276 V, autoranging |
| Current input | Fixed-winding concentric core current comparator (non-galvanic). Ultra Stable range: 5 A ±15% (4.25 A to 5.75 A); operational range 1.25 A to 10 A |
Automation and Interfaces
| RD-22 Ultra Stable | |
|---|---|
| RS-232 | 8-pin RJ-45 jack for PC communication (PCSuite available) |
| Pulse output (port 2) | BNC, open collector, up to 2.1 MHz (200 ns minimum pulse width); selectable Wh, VARh, or VAh; 0.00001 Wh/pulse by default |
| Pulse and gate input (port 1) | BNC, 200 ns minimum pulse width, 20 Hz maximum repetition rate |
| Display and keypad | 4-line by 16-character backlit LCD with a five-button keypad |
Physical, Safety, and Calibration
| RD-22 Ultra Stable | |
|---|---|
| Auxiliary power | External converter, 120 V or 240 V at 50/60 Hz input, supplying 24 V DC to the standard |
| Size | RD-22: 190.5 mm high × 139.7 mm wide × 139.7 mm deep (7.5 × 5.5 × 5.5 in); platform: 19 mm × 152.4 mm × 508 mm (0.75 × 6 × 20 in) |
| Weight | Standard, current comparator, and platform: 5.45 kg (12 lb); auxiliary power converter: 1.36 kg (3 lb) |
| Isolation and withstand | Complete isolation of input, output, power, case, and control; dielectric withstand 2.3 kVrms (60 Hz, 60 seconds); surge withstand IEEE 472 and ANSI C37.90; shock and vibration 50 g |
| Calibration | Software only, with no physical adjustments; 50 Hz or 60 Hz calibration available |
| Recommended calibration interval | 365 days |
| Traceability | NIST-traceable calibration from RADIAN, with ISO/IEC 17025 accredited calibration available, or direct calibration by a national metrology institute |
| ISO/IEC 17025 calibration uncertainty | RADIAN’s accredited capability for watt-hours: ±0.0009% (9 ppm) at unity power factor and ±0.0016% (16 ppm) at ±60° phase angle, over 120 V to 600 V, 0.2 A to 200 A, 50 Hz to 60 Hz, and 5 to 1,000 second tests (A2LA certificate 3784.01) |
| Calibration documents | Sample RD-22 calibration report (ISO/IEC 17025) and ISO/IEC 17025 scope |
RADIAN RD-22 Ultra Stable FAQ
What is the RD-22 Ultra Stable operating range
How is the RD-22 Ultra Stable different from the RD-22
What do the repeatability and reproducibility figures mean
How is the RD-22 Ultra Stable calibrated
What options are available
Related Resources
Strength in Numbers: Reducing Uncertainty with Three RD-22 Primary Transfer Standards
Strength in Numbers: Reducing Uncertainty with Three RD-22 Primary Transfer Standards
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