LF & HF Voltage, Current and Microwave Metrology Section (D#6.02)

LF, HF Voltage, Current & Microwave Metrology Section, contributes by maintaining one of the world's most comprehensive national capabilities for measuring electromagnetic quantities across the spectrum using established National Standards for Low Frequency Voltage & Current upto 1000V & 20A, Microwave Power, Attenuation & Impedance Standards upto 50 GHz along with the associated calibration facilities.

The section also has additional capabilities like programmable Josephson voltage standard (PJVS), cryostat system, E-field, RF I-V impedance analyser, Phasor measurement unit (PMU), nano fabrication facility with the help of Focussed Ion Beam (FIB) system.

We regularly participate in BIPM and APMP key/Supplementary comparisons to establish mutual degree of equivalence with the corresponding standards of the leading NMIs and to ensure internationally recognised traceability of measurements. The CMCs registered in appendix C of BIPM-MRA (https://www.bipm.org/exalead_kcdb/exa_kcdb.jsp?_p=AppC&_q=india&x=68&y=21) has been reviewed and approved in Nov 2014.

Parameters:

  1. Josephson Voltage Standard
  2. PJVS forms the basis for standard of the unit ‘Volt’ in India at par to the international level”
    The uncertainty in measurement of Zener Reference Standards is ± 350 nV at k=2 (inclusive of noise of Zener) at 10V level as per the ISO/IEC 17025:2005.
    CMC: DC voltage (single value) Range: 1 V to 10 V.

  3. E-Field
  4. The E-field using a probe is precisely measured inside an indigenously designed transverse electromagnetic (TEM) cell as per IEEE Std. 1309-2013. Key parameters for precise E-field measurement is explicated with their measurement results such as probe linearity, field distortion, and mismatch losses. E-field strength of probe has been reported 9.91 V/m with an expanded uncertainty (k ~ 2) of ±0.58 V/m for +18 dBm fed power at 915 MHz frequency.

  5. LF Voltage
  6. Establishing traceability and providing apex level calibration services from 1 mV to 1000 V in the frequency range of 10 Hz to 1 MHz with uncertainty from ± 10 ppm to ± 1000 ppm.

  7. LF Current
  8. Providing traceability along with calibration services from 1 mA to 10 A in the frequency range of 40 Hz to 10 kHz and 20 A up to 5 kHz with uncertainty from ± 20 ppm to ± 100 ppm.

  9. Josephson Voltage Standard
  10. Traceability of high frequency thermal voltage converters against the primary standard of HF voltage based on calorimetric principle has been established in the voltage range from 1 mV to 10 Volt up to 1000 MHz with ±1.5 % uncertainty.

  11. Microwave Power
  12. Providing apex level calibration services and dissemination of standards for maintaining the traceability in power measurements up to 10 mW in the frequency range of 1 MHz to 50 GHz with uncertainty up to ± 1.6 %.

  13. Microwave Attenuation
  14. Establishing traceability in attenuation using 30 MHz WBCO attenuator and providing apex level calibration services from 0.05 dB to 60 dB at 30MHz, 1GHz to 18 GHz with uncertainty of ±0.02 dB/10 dB.

  15. Microwave Impedance
  16. Providing apex level calibration services and dissemination of standards for maintaining the traceability in impedance (reflection coefficient/VSWR) measurements in the frequency range 2 GHz to 18 GHz, in coaxial with uncertainty of ±0.02 in VSWR and in the frequency range 5.8 GHz to 18 GHz in waveguide with uncertainty of ±0.002 to 0.004 in reflection coefficient magnitude.

  17. Nano-Fabrication Lab: FIB
  18. FIB lab work on the synthesis and fabrication of nanodevices and nanostructures to study the quantum transport properties, understanding the enhancement in the device functionality and validating their future implementation for establishing quantum metrology related activities and applications.

  19. Phasor Measurement Unit Calibration system
  20. Evaluates the total vector error (TVE), frequency error (FE), and rate of change of frequency error (RFE), then compares those results with the original stimulus. Evaluation done against the thresholds defined in IEEE Std C37.118.1a-2014. Voltage and current are generated with up to six digits precision and accuracies better than 0.005% (50 ppm). Phase adjustment provides for 1 milli-degree or 10 micro-radian resolutions. Phase performance is exceptional, with voltage to current phase accuracy to 2.3 milli-degrees. Voltage-to-voltage phase accuracy is 5 milli-degrees.

  21. RF I-V Impedance Analyser
  22. Calibration and measurements of dielectric parameters of low lossy materials is carried out using E4991A RF I-V impedance analyzer with 16453A test fixture

  23. Specific Absorption Rate (SAR) Measurement system
  24. Technical partnership with Telecommunication Engineering Centre (TEC), Govt. of India for Mandatory Testing and Certification of Telecom Equipment (MTCTE) program with indigenously developed Specific Absorption Rate (SAR) evaluation system by CSIR- NPL. The system is capable to evaluate SAR upto 3W/kg with an expanded uncertainty of ±0.15W/kg per 1.6W/kg.

  25. Upcoming Calibration Services
  26. Plan is underway to enhance our measurement capabilities by Upgradation of LF current calibration facility up to 100A and setting up of Oscilloscope and oscilloscope calibrator calibration facility.

  27. Keycomparisons
  28. List of Key Comparisons

Scientist Technical Person
Dr. Saood Ahmad Ms Archana Sahu
Dr. Sudhir Hussale Ms. Mandeep Kaur
Dr. V. K. Toutam Ms. Sunidhi Luthra
Dr. S.K. Dubey Ms. Swati Kumari
Ms. Sandhya M. Patel Mr. Anish Bhargav
Mr. Anurag Reddy Ms. Jyoti Chauhan

Contact Person:

Dr. Anurag Gupta
Email ID: ahmads@nplindia.org

JOSEPHSON VOLTAGE STANDARD (PJVS)

The PJVS system is based on ‘Quantum Phenomena’ (Josephson effect) given by the relation 2eVn = nhf where n = 0, ± 1, ± 2, ± 3.., Vn = quantized voltage, f = frequency of irradiation, h = Planck’s constant, e = electron charge.
The salient features of the system are:

  • The non-hysteretic Josephson tunnel junctions made up of Nb electrodes and NbxSi1-x barriers.
  • The 10 V chip contains a total of 256,116 Josephson junctions organised in stacks of three junctions and distributed into 32 microwave coplanar waveguide lines.
  • The voltage steps are stable, have superior immunity to noise and have rapid settling time.


(a) 10 V - PJVS at NPL-India, established in the collaboration with NIST, USA
(b) I-V curves for 23 subarrays and Step flatness test at 18.645 GHz and 0.00 dBm.

“PJVS forms the basis for standard of the unit ‘Volt’ in India at par to the international level” The uncertainty in measurement of Zener Reference Standards is ± 350 nV at k=2 (inclusive of noise of Zener) at 10V level as per the ISO/IEC 17025:2005.

CMC: DC voltage (single value) Range: 1 V to 10 V.

CRYOSTAT SYSTEM

The system is capable to measure transport properties of superconducting thin films and devices at low temperature (down to 1.6 Kelvin) with microwave (up to 40 GHz) and magnetic field (up to 110 Gauss)


(a) Cryostat System at CSIR-NPL    (b) R-T curve of thin aluminum wire, Tc at 1.8 K.

Basic Principle: Samples are cooled by insertion into flowing helium gas exiting from the vaporizer. Pumping on the sample zone provide temperatures below 2 K. Liquid helium flows from the reservoir through the adjustable flow valve down to the vaporizer located at the bottom of the sample tube. Applying heat vaporizes liquid and raises gas temperature. This gas then cools the sample.

DESIGN DEVELOPMENT AND MEASUREMENT OF A SHIELDED CHAMBER TO SERVE AS E- FIELD STANDARD OF THE COUNTRY TO PROVIDE PRECISE MEASUREMENT TRACEABILITY FOR MOBILE TOWER RADIATION MEASUREMENT PROBE AS PER IEEE STD. 1309-2013.

This solution elaborates the theoretical and measurement technique to evaluate precise and accurate electric (E)-field strength for frequency range 0.8–2.4 GHz (2G and 3G and 4G communication spectrum). The E-field using a probe is precisely measured inside an indigenously designed transverse electromagnetic (TEM) cell as per IEEE Std. 1309-2013. Key parameters for precise E- field measurement are explicated with their measurement results such as probe linearity, field distortion, and mismatch losses. E-field strength of probe has been reported 9.91 V/m with an expanded uncertainty (k ~ 2) of ±0.58 V/m for +18 dBm fed power at 915 MHz frequency.
Narang N., Dubey S.K., Negi P.S., and Ojha V.N.,m “ Design and Characterization of E- shaped Microstrip based E-field Sensor for GSM and UMTS Frequency Bands,” AIP Review of Scientific Instruments, vol. 87, no.12, p.124703, 2016.
Narang N., Dubey S.K., Negi P.S., and Ojha V.N. “Accurate and precise E-field measurement for 2G and 3G networks based on IEEE Std. 1309-2013,” Microwave and Optical Technology Letters, 57(7), 1645-1649, 2015.


Fig. 1. Experimental setup for E-field measurement inside indigenously designed TEM cell

LOW FREQUENCY VOLTAGE

Traceability of thermal voltage converters covering voltage range 250 mV to 1000 V in the frequency range 10 Hz to 1 MHz has been established to the primary standard of LF voltage (Bank of multijunction thermal converter, uncertainty + 10 ppm at 2V). Traceability of low voltage (1 mV to 300 mV) measurements has been covered using micro-potentiometers and thermal transfer standard Fluke 792A.

  AC-DC Voltage Transfer Difference

Traceability:

NPL maintains its primary and transfer standards at par with corresponding standards of leading NMIs such as PTB, Germany; NMI, Australia; NIST, USA etc. The degree of equivalence of our standards with the corresponding standards of these countries has been established by participation in BIPM, APMP and supplementary comparisons

Parameter Range Uncertainty
Low Frequency Voltage 10Hz -1MHz 1mV-1000V ± 0.001%- ± 0.1%

Periodicity:

Maximum two years

Area of consultancy:

It can be given in any specialized work involving the above parameters including setting up of a laboratory, training of personnel on measurement techniques and method of uncertainty evaluation.


AC-DC Current Transfer difference

Parameter Range Uncertainty
Low Frequency Voltage 40Hz - 10kHz 1mA-20A ± 0.002%- ± 0.01%

HF VOLTAGE

High frequency (HF) voltage primary standard at NPLI has been realized using a twin resistance coaxial power mount fitted with two tiny resistors which provides proper termination of 50 ohm at the end of coaxial line in the frequency range of 1 MHz to 1000 MHz. The rf/dc transfer difference has been assigned to HF voltage primary standard. This is the key technique for the realization of HF voltage primary standard and its traceability is obtained by assigning effective efficiency, RF impedance and the DC resistance to it against each of the parameters’ reference standard. Measurements are done at the input reference plane of the primary standard. Therefore, measurement uncertainty in assigning the rf/dc transfer difference to the primary standard is the cumulative effect of the uncertainty in determination of effective efficiency, HF impedance and the DC resistance. With the establishment of the HF voltage primary standard, one can calibrate and assign the rf/dc transfer difference to the transfer standard thermal voltage converters.

Parameter Range System Unc.
HF Voltage 1mV to 10V 1MHz to 1GHz HF TVC ± 1.5 %

Calibrating instruments includes:

  • RF Millivoltmeter with probe
  • Level meter

MICROWAVE POWER

The function of Microwave Power Section is to provide apex level calibration services and dissemination of standards for maintaining the traceability in microwave power measurements up to 10 mW in the frequency range of 1 MHz to 50 GHz with uncertainty up to ± 1.6 %

Beside this, laboratory activities include internal trainings, establishment of new set-ups according to measurement/calibration and consultancy needs and forming traceable calibration procedures as per ISO 17025.

Present capabilities:

Coaxial Microcalorimeter system in 2.4mm connector, established as the primary standard of Microwave Power in the frequency range of 1 MHz to 50 GHz is an absolute method based on thermocouple principle for the determination of effective efficiency to the thermocouple sensor.

2.4mm Coaxial Microcalorimeter Coaxial Thermocouple sensor Direct Comparison Technique

Coaxial thermocouple sensors, which are assigned calibration factors using coaxial microcalorimeter system, are used as reference standards to calibrate power sensors / thermistor mounts using direct comparison technique. VSWR is measured at all the desired frequencies with the help of Vector Network Analyzer based technique.

Calibrating instruments includes:

  • Coaxial Thermistor Mounts
  • Power meter with Power sensors
  • RF Power Transfer Standard
  • Signal Generator
  • Spectrum Analysers
  • Frequency Counters/Universal Counter

For Calibration Charges please click on the given link :
http://www.nplindia.in/calibration-charges-d203b-lf-hf-voltage-current-microwave-standards-wef-01042018


30 MHz waveguide below cut off (WBCO) Attenuator

Attenuation measurements over the frequency range 30 MHz to 18 GHz are based on an IF substitution system using 30MHz attenuator and signal calibrator. The measurement frequency is down-converted to 30 MHz, at which it is traceable to primary standard of NPLI.


RF Attenuation Inter-comparison

NPLI offers a calibration service for the coaxial step attenuators and rotary vane attenuator (wave guide). Attenuation values from 0.05 dB to over 60 dB can be measured, depending on the frequency of measurement. In view of the wide range of options on attenuation range and frequency band customers are requested to consult CFCT, NPL on the cost and details for calibrations requirements.

MICROWAVE IMPEDANCE

The microwave impedance measurement is an essential requirement for evaluating and improving the matching properties of microwave components and sub-systems. At microwave frequencies, S-parameters are most appropriate representation of microwave impedance.
The impedance of a precision co-axial airline can be calculated in terms of its dimensions and conductivity of material used that’s whys it is considered as a primary standard of impedance above 2 GHz. Uncertainties involved in such a calculation increase rapidly with the number of different materials involved in the construction and the complexity of the electromagnetic fields.
For coaxial transfer standards coupled sliding load technique (2 -18 GHz) and for wave guide system tuned reflectometer technique (5.8-18 GHz) have been established. Reflection coefficient / VSWR of the one port/ two port commercially available transfer standards are measured.
Broadband S-parameter measurements on one/two port artefacts in Type-N, APC-7 connector upto 18GHz
Primary and transfer waveguide standards (Ku band)
S- Parameters measurements are performed using a vector network analyzer (VNA). For These measurements the VNA must first be calibrated. Below two 2 GHz VNA is calibrated using Short-Open-Load (SOL) technique and using LRL above 2 GHz.
In view of the wide range of Reflection coefficient / VSWR and frequency band customers are requested to consult CFCT, NPL on the cost and details of the measurements or calibrations required.

PHASOR MEASUREMENT UNIT CALIBRATION SYSTEM

This facility is used for calibration and performance evaluation of phasor measurement units (PMU) for wide area real time control. Today’s smart grid relies on PMUs to deliver real-time, mission critical data on the voltage, current, frequency and phase within the distribution grid. To ensure consistent, accurate and credible PMU data, it is essential that PMUs be properly calibrated. The Phasor Measurement Unit Calibration System is an ideal system for national metrology institutes (NMIs) to provide a perfect solution for third party calibration houses, electrical power utilities and organizations associated with electrical power transmission. As this system includes a three-phase Electrical Power Calibration Standard, you can also use it to calibrate wide workload of electrical power and power quality test instruments. The integrated PMU-CAL system fully complies with the IEEE C37.118.1a-2014, IEEE Synchrophasor Measurement Test Suite Specification-Version 2-2015 and C37.242-2013 standards for PMU operation and verification. The system also fully complies with the 2016 draft standard IEC/ IEEE 60255-118 Ed.1.

The PMU CAL system enables:

  • Calibrate and test a PMU from a client PC
  • Quickly set up a PMU test
  • Speed through automated calibration procedures or interactively do custom PMU testing
  • Provide the required static and dynamic voltage and current conditions that occur in a power distribution grid specified by the standard
  • Apply those signals to a phasor measurement unit
  • Capture the PMU’s reported results

  • Phasor Measurement Unit Calibration System

  • Evaluate the total vector error (TVE), frequency error (FE), and rate of change of frequency error (RFE)
  • Compare those results with the original stimulus
  • Evaluate against the thresholds defined in IEEE Std C37.118.1a-2014
  • Create test reports, graphs and calibration certificates that can be readily printed or shared electronically

The system is made up of these hardware components with an integrated test connection:

  • Three-phase Electrical Power Standard: Includes one Electrical Power Standard Master Unit and two Electrical Power Standard Auxiliary Units. Provides voltage and current stimuli to the PMU under test.
  • System Timing Unit: controls timing and synchronizes the tests done throughout the calibration system
  • GPS receiver: supplies the PMUCAL system and the PMU under test with a source of Universal Coordinated Time (UTC)
  • Server PC: functions as a dedicated application controller, receiving commands from the client PC to control the calibration system

The Electrical Power Standard Three Phase System at the heart of the PMU calibration system can be operated in standalone mode, independent of the System Timing Unit and the server PC. The sets a new benchmark for accuracy in electrical power calibration standards. Voltage and current are generated with up to six digits precision and accuracies better than 0.005% (50 ppm). Phase adjustment provides for 1 milli-degree or 10 micro-radian resolutions. Phase performance is exceptional, with voltage to current phase accuracy to 2.3 milli-degrees. Voltage-to-voltage phase accuracy is 5 milli-degrees. Use this system to generate a wide variety of complex signals, including flicker; harmonics; dips and swells; inter-harmonics; fluctuating harmonics; simultaneous application.
This feature gives us enormous flexibility to calibrate a wide workload of electrical power test instruments.

RF I-V IMPEDANCE ANALYZER

Calibration and measurements of dielectric parameters of low lossy materials is carried out using E4991A RF I-V impedance analyzer with 16453A test fixture. Open ended coaxial probe based dielectric parameter measurements are performed for higher frequency using Vector Network Analyzer. It is a Measurement and Calibration setup for high lossy dielectric materials.
Research work is also being undertaken for template assisted fabrication of Microwave absorbing materials and specialty dielectrics as reference standard (BND) for microwave metrology.

Measurement setup of Solid dielectric parameters using RF I-V impedance analyser

E4991A RF Impedance/Material Analyzer 16453A Dielectric Material Test Fixture

NANOFABRICATION FACILITY AT CSIR-NPL: FIB LAB

FIB lab work on the synthesis and fabrication of nanodevices and nanostructures to study the quantum transport properties, understanding the enhancement in the device functionality and validating their future implementation for establishing quantum metrology related activities and applications. It is believed that nanofabrication will be very essential tool for the next generation’s technologies and metrological standards will be truly based on quantum phenomena. As per this mandate, we have fabricated superconducting meander lines, very thin superconducting nanowires or nanostructures, proximity coupled 2D layered material-based junctions, superconductor 2D electronic gas superconductor junctions, topological insulators-based devices etc. that have very useful metrology applications. Further, FIB lab also works on the fabrication and characterization of calibration artifacts, samples from the textile, pharma and biotech industries e.g. Drug Eluting Stent System (DES).

Characterization / fabrication parameters:

  1. Quantitative elemental analysis using energy-dispersive spectrometry (EDS)
  2. Dimensional measurements of nanostructures using FESEM (Zeiss Auriga)
  3. Device Fabrication using focused ion beam microscopy and ebeam lithography

Establishment of Indigenous Specific Absorption Rate Measurement System (SAR W/kg) for Mobile Exposure Assessment on Human Being during communication
Statement: Technical partnership with Telecommunication Engineering Center (TEC), Govt. of India for Mandatory Testing and Certification of Telecom Equipments (MTCTE) program with indigenously developed Specific Absorption Rate (SAR) evaluation system by CSIR- NPL. In this setup E-Field Sensor, Tissue equivalent liquid, Robotic automation and a controlled GUI are being indigenously developed. The system is capable to evaluate SAR upto 3W/kg with an expanded uncertainty of ±0.15W/kg per 1.6W/kg.


Fig. SAR measurement setup at CSIR-National Physical Laboratory


Fig. SAR measurement setup at CSIR-National Physical Laboratory

DDG Radio approved CSIR-NPL technology for commercial compliance testing of mobile phone SAR based on IEEE-1528 2013 and IEC-62209-1,2 (Technology Developed). A very first center will be established at TEC, New Delhi based on this technology as transfer standard.

UPCOMING CALIBRATION SERVICES

We are planning to enhance our measurement capabilities by providing calibration services for the following parameters:

Upgradation of LF current calibration facility up to 100A.


High Current calibration Measurement Setup

Oscilloscope and oscilloscope calibrator calibration facility at NPL.


Oscilloscope Calibration

CONTACT INFORMATION