| 1. |
- Ahlers, F.J., et al.
(författare)
-
The EMRP project GraphOhm- Towards quantum resistance metrology based on graphene
- 2014
-
Ingår i: CPEM Digest (Conference on Precision Electromagnetic Measurements). - 0589-1485. - 9781479952052 ; , s. 548-549, s. 548-549
-
Konferensbidrag (refereegranskat)abstract
- A new joint research project (JRP) integrating metrology institutes and universities from nine countries is aimed at realization of a new generation of standards for quantum resistance metrology. The project exploits graphene's properties to simplify operation of standards without compromising the unprecedented precision delivered by semiconductor quantum Hall devices. Higher operating temperatures (above 4.2 K, and up to 8 K) and together with lower magnetic fields (below 5 T, and potentially down to 2 T) will lead to a significantly improved and cost-saving dissemination of intrinsically referenced resistance standards to all end-users relying on electrical measurements.
|
|
| 2. |
- Andersson, Bengt-Olof, et al.
(författare)
-
Calibration of Gain Ratios on nV-Meters with the Reference Step Method
- 2018
-
Ingår i: CPEM 2018 - Conference on Precision Electromagnetic Measurements. - 9781538609736
-
Konferensbidrag (refereegranskat)abstract
- The Reference Step Method for calibrators can be modified for calibration also of the gain ratios on a meter. The method has earlier been evaluated in the range 100 mV-1000 V on DMM HP 3458A1 and shows that an accuracy of typically < ± 0.2 μ V/V could be obtained. We have investigated the performance of the method when calibrating ratios in the range 1 mV-100 mV on two common nV-meters. In our comparisons with the Josephson Voltage Standard the differences are within ± ± 12μ V/V at the ratio 10m V:1mV and within ± ± 1.3μ V/V at 100mV:10mV.
|
|
| 3. |
|
|
| 4. |
- Bergsten, Tobias, et al.
(författare)
-
An active filter for Delta-Sigma modulated Josephson waveforms
- 2014
-
Ingår i: CPEM Digest (Conference on Precision Electromagnetic Measurements). - : Institute of Electrical and Electronics Engineers Inc.. - 9781479952052 ; , s. 518-519
-
Konferensbidrag (refereegranskat)abstract
- We present an active low pass filter constructed for Delta-Sigma modulated Josephson waveforms. The filter has a fifth order Butterworth characteristic with high input impedance and stable passband performance, including dc. We present results from frequency response, input impedance characteristics, passband ac-dc measurements and spectra of a Delta-Sigma modulated sine wave from a programmable Josephson voltage standard.
|
|
| 5. |
- Bergsten, Tobias, et al.
(författare)
-
An Active Filter for Delta-Sigma-Modulated Josephson Waveforms
- 2015
-
Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; 64:6, s. 1559-1563
-
Tidskriftsartikel (refereegranskat)abstract
- We present the design and electrical characteristics of an active low-pass filter. It will be used in a reference waveform source based on a programmable Josephson voltage standard with multilevel delta-sigma modulation to generate accurate and spectrally pure arbitrary waveforms. The filter has a fifth-order Butterworth characteristic with high input impedance, low distortion, high stopband attenuation, and stable passband performance, including dc.
|
|
| 6. |
- Bergsten, Tobias, et al.
(författare)
-
An electrical power reference system Up to 1 MHz
- 2016
-
Ingår i: Conference on Precision Electromagnetic Measurements (CPEM 2016).
-
Konferensbidrag (refereegranskat)abstract
- We present a reference system for calibration of electrical power at frequencies up to 1 MHz. The system consists of several components and we have developed methods of calibrating the components in order to ensure traceability to the SI units. The reference system is designed for steady state sinusoidal signals and gives a preliminary uncertainty of 50 μW/VA at frequencies up to 1 kHz, and 10 mW/VA at 1 MHz.
|
|
| 7. |
|
|
| 8. |
- Bergsten, Tobias, et al.
(författare)
-
Comparison between GaAs and graphene QHR standards for resistance realisation at SP
- 2016
-
Ingår i: Conference on Precision Electromagnetic Measurements (CPEM 2016). - 9781467391344
-
Konferensbidrag (refereegranskat)abstract
- We report the first precision QHR measurements at SP using a graphene chip. We compare the results of a resistance calibration using GaAs based chips with the results using a graphene chip. The results agree within a few parts in 109 for calibrations of 100 Ω and 10 kΩ resistors. Consistency checks indicate that the uncertainty is lower with the graphene chip, and the noise level is slightly lower. The measurements with the graphene chip were performed exclusively at 4.2 K, which simplifies the calibration procedure considerably compared with GaAs chips.
|
|
| 9. |
- Bergsten, Tobias, 1970
(författare)
-
Coulomb Blockade Thermometry and Other Aspects of Tunnel Junction Arrays
- 2001
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This report describes experimental results on a few different aspects of two-dimensional tunnel junction arrays: Coulomb blockade thermometry (CBT), Hall effect and Josephson array magnetometry (JAM). CBT is a primary thermometry method which is only a few years old. It is suitable for cryogenic temperatures between 20 mK and 30 K. The primary nature, the small size, the speed of operation and the low sensitivity to magnetic field, neutron radiation and nonuniformities in the array makes it a good choice for general laboratory work. We have investigated some new possibilities which can improve this technique. We show that in addition to one-dimensional (1D) arrays which were originally used, we can also use 2D arrays and achieve better results above 1 K. The main advantages are better robustness to nonuniformities in the array or broken/shorted junctions, lower noise and faster measurement due to lower resistance. We present a faster primary measurement method for CBT which is based on the third derivative of the current-voltage characteristics. This third derivative has a zero crossing at a well defined temperature dependent voltage. We demonstrate a feedbacked measurement circuit which is able to follow this zero crossing. We have also measured Hall resistance in superconducting arrays. We report a complex structure in the magnetic field dependence of the Hall resistance. We see that the Hall resistance only appears in certain ranges of the junction parameters. We also see that in some cases a gate voltage can affect the Hall voltage strongly, even change the sign of the Hall resistance. We were also able to increase the periodic fluctuations of the ordinary resistance in an array by ten times by aplying a magnetic field of 30-50 mT. The JAM experiments are very preliminary and we just briefly report on the first data we have taken. We hope to be able to use the S-I transition in a Josephson junction array as a megnetic field sensor.
|
|
| 10. |
- Bergsten, Tobias, et al.
(författare)
-
Determining voltage dependence of the phase response in voltage dividers
- 2012
-
Ingår i: Conference on Precision Electromagnetic Measurements, CPEM 2012. ; , s. 282-283
-
Konferensbidrag (refereegranskat)abstract
- We have developed methods to characterise voltage dependence of the phase response in voltage dividers. The voltage dependence is a combination of two parts, a linear dependence and a power dependence due to voltage and temperature dependence in capacitors respectively. The standard uncertainty of the phase at 240 V and 100 kHz is estimated to be 20 μrad.
|
|
